West, Ian M. 2013. Dinosaur footprints in Jurassic-Cretaceous boundary beds on the Isle of Portland: Geology of the Wessex Coast (Jurassic Coast - World Heritage Site). Internet field guide. http://www.southampton.ac.uk/~imw/portdino.htm. Version: 18th December 2013.

Dinosaur Footprints in Jurassic-Cretacous boundary beds on  the Isle of Portland

Ian West,
Romsey, Hampshire

and Visiting Scientist at:
Faculty of Natural and Environmental Sciences,
Southampton University,
Webpage hosted by courtesy of iSolutions, Southampton University

Aerial photographs by courtesy of The Channel Coastal Observatory , National Oceanography Centre, Southampton.

|Home and Contents |Maps and Introduction |Portland - Geological Introduction |Portland Bill |Portland - dinosaur footprints |Portland - Mutton Cove to Wallsend |Portland Harbour |Withies Wall, Portland |Portland Group Fossils |Chesil Beach |Chesil Beach Pebbles |Chesil Beach Lodestone, Magnetite |Portland Bibliography |Bibliography of the Purbeck Formation |Durlston Bay - Peveril Point, Upper Purbeck Formation |Durlston Bay, Middle Purbeck Durlston Bay - Lower Purbeck |Durlston Bay - Central Zigzag Part & Coast Erosion |Durlston Head - Lower Purbeck Formation & Portland Stone |Durlston Bay - Bibliography

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Three dinosaur footprints with possible slip towards a large depression, Hard Slatt, Isle of Portland Ornithopod testing the salt-crust before placing a foot firmly down? Ornithopods enter the Purbeck forest at the edge of the salt lake (painting by Anthea Dunkley)

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ISLE OF PORTLAND -LIST OF FIELD GUIDES AND BIBLIOGRAPHIES

Isle of Portland - Geological Introduction

Isle of Portland - Geology of the Inland Quarries
Portland, West Side, Mutton Cove to Wallsend
Portland, West Side, Mutton Cove to Wallsend
Portland Bill Geology
Portland Harbour
Withies Wall, Quarry Section, northern Isle of Portland
Portland Group Fossils
Chesil Beach - Introduction
Chesil Beach Pebbles
Chesil Beach Lodestone, Magnetite Occurrence
Chesil Beach - Storms and Sea Defences
Chesil Beach - Bibliography and References
Dinosaur Footprints, Purbeck Formation, Isle of Portland (this webpage)
Bibliography of Portland and Portland Stone Geology

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INTRODUCTION:

General:

Slabs of the Hard Slatt, some with footprints,  from the Lower Purbeck Formation, Isle of Portland

Dinosaur footprint slabs of Portland, lifting in progress. With Richard Edmonds and Ian West

Several different types of relatively small dinosaur footprints have been found in slabs of limestone from the Purbeck Formation on the Isle of Portland, Dorset. They have already been figured to a limited extent in a report by Edmonds et al. (2002 ). More than 70 individual tracks, mostly three-toed, have been found so far. Some of these are in trackways of several prints. Both herbivorous Ornithopod and carnivorous Theropod dinosaur tracks have been found during the preliminary observations. Some anomalous tracks seem to have the central toe impression either missing or very feebly impressed. They are difficult to explain because they do not have the correct symmetry for a dromaeosaur print with a raised claw, although an origin from this type of dinosaur was first considered as a possible explanation. Small, apparently juvenile, prints from a "baby" ornithopod are present. Richard Edmonds of the Devon-Dorset World Heritage Coast (Jurassic Coast) section of Dorset County Council is supervising both study and conservation on the slabs. Grateful acknowledgement is made to Hanson for allowing access and for conserving the specimens, which are their property. This present webpage is merely an initial photographic record of the finds as they are made, not the full scientific study which will follow. Its purpose is to ensure that early observations are recorded and little is lost, but any interpretive comments should be regarded as provisional and subject to revision at a later stage. It is intended that the full scientific study will by dinosaur footprint specialist - Paul Ensom of the Natural History Museum, London. His investigation will commence in October 2003. A useful undergraduate project by Caroline Clasby (2003) has discussed the environment of deposition and the research potential of the tracks. Her work took place when the main set of tracks was visible, but before the moving of some of the slabs by crane in September 2003, which revealed some new types of footprints.

Other interesting fossil remains are present in associated strata. In addition to the footprints Richard Edmonds has a dinosaur bone from adjacent strata. An impressions that appear to be of reptile skin has been found by Stuart Tabner in marl associated with dinosaur slabs. To avoid damage or loss of tracks the exact location on the Isle of Portland is not given here.

Dinosaur footprints are well-known features of the Purbeck Formation, mostly of early Cretaceous age (Berriasian) of Dorset. The basal part of the Purbeck Formation is uppermost Jurassic. They have been found particular in quarries and cliffs which expose the Middle Purbeck lagoonal and shelly limestones. They deposits are sub-humid origin at a palaeolatitude of about 37degrees north. A few have been found in Upper Purbeck strata and they are well-known in the Wealden strata which follow but usually in other parts of southern England. For a valuable review and a comprehensive bibliography of Purbeck dinosaur tracks and trackways see Ensom (2002) .

Although tracks also occur in the Lower Purbeck Formation which originated in dryer, semi-arid conditions, they are much less common in this part of the sequence. The Isle of Portland, a peninsula in the middle of the Dorset coast, does not seem to contain any significant amount of Middle Purbeck strata because it has been removed by erosion. There are some blocks moved by solifluction into the debris of a Pleistocene raised beach and there is the possibility of a very small amount existing near Southwell, but this is unlikely. Thus the most promising horizons for footprints are missing and until recently no footprints had been found. However, in 1996 a single tridactyl dinosaur footprint was discovered by Dr Jane Francis in the Transition Bed at the very base of the Purbeck Formation near Freshwater on the east side of the peninsula. On the basis of recent dating (not an easy matter because of the lagoonal rather than marine facies) by (Feist, Lake and Wood, 1995) this would be of very late Jurassic age. No others were found on Portland until a few years later a dog-walker noticed footprints in large slabs of Lower Purbeck limestone which had been tipped on the grass at the top of an active quarry. The quarry manager, Ben Murray, was kind enough to initially protect and preserve these and draw attention to them by email. Thanks to his interest and that of Richard Edmonds of Dorset County Council, they became a subject of initial studies with the prospect of a full investigation later. These footprints occur in blocks of the so-called "Hard Slatt" which is clearly seen to be present in the Lower Purbeck sequence between the Caps and Dirt Beds of the basal Purbeck and the gypsum (Portland Alabaster) of the Soft Cockle Member of the Lower Purbeck Formation. The present author considers the Hard Slatt to correspond to the Hard Cockle Member of the Lower Purbeck Formation which is a prominant limestone with similar high-energy (relatively), cross-laminated, carbonates and similar pseudomorphs after halite. The Hard Cockle Member can be examined at Lulworth Cove and adjacent area. Using the correlation of (Feist, Lake and Wood, 1995) this would be basal Cretaceous. It is very close to the Jurassic-Cretaceous boundary, although the position of this is not known with great precision.

Very well-preserved, but relatively small, dinosaur footprints occur in the slabs. Several of them are associated with the salt crust of a salt lake. Photographs and preliminary descriptions are given here with emphasis on the unusual limestone in which they occur and the sedimentary structures which are present. These help in understanding the palaeoenvironment. The preservation of the footprints is now under the control of Richard Edmonds of Dorset County Council and he has already published photographs of them. This webpage is a branch of the general Geology of the Isle of Portland webpage, and that should be referred to for background information on the geology of the Purbeck Formation on Portland in which the dinosaur footprints occur. It also provides maps and sections and information on various geological localities on the peninsula and various fossil remains.

The reader wishing to understand dinosaur footprints in general should see the excellent introduction - "Tracking Dinosaurs" - by Lockley (1991) . For more advanced and detailed study see - "Dinosaur Tracks and Traces" - a symposium of many papers on the subject and edited by Gillette and Lockley (1989). The Lower Cretaceous Wealden dinosaurs of the nearby Isle of Wight are well-described by Martill and Naish (2001) . Lower Cretaceous dinosaur footprints are discussed here too.

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INTRODUCTION:

Safety on Field Trips on Portland

Before discussing the footprints the matter of safety, therefore requires attention. General information regarding safety on Dorset geological field trips is provided in a separate webpage and you are requested to read this.

There are various hazards with regard to Portland and great care should be taken with cliffs, rocks and boulders, quarries and quarry machinery. Specific risk regarding the dinosaur footprints are mentioned here. There is some risk in scrambling over blocks of stone in the search for footprints. It is very easy to slip and fall from the sloping slabs when studying or photographing them and great care must be taken. Since at times relatively few people may pass the blocks incapacity resulting from a slip amongst the blocks could be very dangerous, especially in bad weather. While there is no safe and easy access to them they are not recommended for visits by school parties.

There is always a hazard of falling rocks, and in quarries the rock is often loose and even more likely to fall. Safety helmets should always be worn beneath cliffs and in quarries, and any places with loose rock or where it is clear that rock has recently fallen should be strictly avoided. Quarry regulations must be followed if these are visited and care taken to keep clear of heavy plant and machinery and loose rocks. High-visibility tabards may be needed. It is important not to hammer the chert in the Portland and Purbeck strata because dangerous splinters can easily penetrate the body and may cause blindness. When preoccupied in geological work take care not to walk backwards over a quarry cliff or fall down fissures in the Portland Stone. A hazard of injury exists if persons attempt to lift a large block of stone.

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FOOTPRINTS:

The Portland Dinosaur Footprints - The Footprint Slabs

Moving the dinosaur footprint blocks from the pile at the quarry

Richard Edmonds supervising lifting of a dinosaur footprint slab, Isle of Portland, Dorset

Slab with dinosaur footprints is swung away, Isle of Portland, Dorset

Dinosaur footprint slab, lowered

The best of the dinosaur footprint slabs have recently been lifted out of the pile of blocks to be placed in a safe and secure site. In due course it is hoped that they will be on public display, but this will take time. The study of the slabs and arrangements for their future is in the hands of Richard Edmonds from the Dorset-Devon World Heritage Coast (Jurassic Coast) section of Dorset County Council. Richard is shown in the above photographs. The moving of the slabs is by courtesy of Hanson Quarries, who are the owners of the fossils.

Typical dinosaur slab with amateur geologists

A typical slab from the Hard Slatt is shown here, together with enthusiastic amateur geologists, including the Tabner family who have helped by searching the smaller blocks of laminated limestone associated with the dinosaur slabs. Their help is much appreciated. Stuart Tabner discovered the strange markings on a thin limestone, probably from above the dinosaur footprint bed, and discussed below.

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STRATIGRAPHY:

The Hard Slatt, Dinosaur Footprint Bed, and Associated Strata

The Hard Slatt in the Purbeck strata at Mutton Cove

The Hard Slatt Bed in situ is shown in the cliffs south of Mutton Cove. Underneath the Hard Slatt is the Shingle, rather crumbly, ripple-bedded, argillaceous and sandy limestone. This is probably the equivalent of the Linsen Shale, beneath the hard limestone of the Hard Cockle Member and a conspicuous bed in the Lulworth Cove and Worbarrow area. This contain sand linsen or lenses of ripple origin and within shale. The sand is mostly carbonate sand.

Lower Purbeck succession with the Hard Slatt, Mutton Cove to Wallsend

Above is shown the succession in the cliffs from Mutton Cove to Wallsend to show the stratigraphical position of the Hard Slatt in relation to associated strata. The succession ranges from mildly hypersaline strata to evaporites including gypsum.

Thick Hard Slatt in cliff-top ledge, Mutton Cove

Here is a cliff-top exposure of the Hard Slatt at Mutton Cove. There are well-developed ripple marks on the top surface of the bed. A dinosaur footprint is visible within the Hard Slatt.

Position of Hard Slatt in part of Coombefield Quarry, northern face

Hard Slatt in the northern part of Coombefield Quarry

Hard Slatt with herring-bone cross-stratification, northern part of Coombefield Quarry, Portland

Southwestern face of Coombefield Quarry, Isle of Portland

Purbeck succession in the southern part of Coombefield Quarry, Isle of Portland

The Hard Slatt can be seen in several quarries in the central part of the Isle of Portland. The images above show the bed in both the northern and southern parts of Coombefield Quarry. It is to some extent variable in thickness and often thinner than in the blocks with footprints. It is frequently fractured and partly obscured by associated marly debris. It is thus not as obvious in the quarry cliff face as might be expected.

The dinosaur footprints are present in some very large and heavy slabs that have been removed by machines with other overburden from above Portland Stone in a working quarry. The site is within the quarry property and is to some extent protected and under observation. It is not accessible to vehicles except through the working quarry. The slabs are not systematically arranged and footprints occur here and there in slabs at all angles. Some slabs are the right-way up and these normally show a rippled surface. The footprints are seen as natural casts on some of those slabs which are inverted. The footprints are generally at or near the base of the bed, but not necessarily confined to the exact base. The slabs are joint-bounded with some slickensides showing strike-slip movement and with some travertine with stalactitic structures on certain faces.

Bottom centre and right: The dinosaur footprint bed or Hard Slatt is clearly visible in several quarries. Shown here is the position of this bed in a sequence of Lower Purbeck marls and clays with limestones at Coombefield Quarry, near Southwell. Here, the bed is distinctive with a thickness of near a metre (at maximum) and with a rippled top and halite casts below.

Dinosaur footprints, Hard Cockle Member, Lower Purbeck Formation, Portland

Dinosaur footprints -oblique view

Fairly close view, dinosaur footprint

Dinosaur footprints are shown in the photographs above. These have come from the Hard Slatt which seems to correspond to the Hard Cockle Member of the Lower Purbeck Formation, which is better known on the mainland of Dorset. There appear to be more than one type. The examples with the very rounded toes (type 1) could be from an ornithodpod dinosaur like the Iguanodonts but smaller. Several of the prints seem to have been impressed into a salt crust (discussed below), with a raised impact rim or bourrelet around them. This rim is now seen in the casts from beneath so that it appears to descend around the margins into the inverted block of limestone. Some footprints (type 2) have no impact rims and these seem to be from a higher level in the bed of calcarenite.

The footprints discussed here are present at or near the base of the Hard Slatt, the equivalent on the Isle of Portland of the main limestone, the Hard Cockle Oolite, of the Hard Cockle Member on the Dorset mainland. Some possible, but very uncertain, footprints from this bed at Worbarrow Tout are discussed below.

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STRATIGRAPHY:

The Underlying Spore Beds

Marl and shaley marl with spores and pollen, under Hard Slatt, Portland

Beneath the Hard Slatt are thin-bedded marlstones or argillaceous limestones, each about a centimetre thick, alternating with very thin grey clays or marls (often less than 1 mm thick). These beds represent the relatively argillaceous top of the Shingle, a sequence of ripple-laminated limestones. If the sequence is regarded as cyclical this part is the regressive top of a cycle and analogous in terms of position within a cycle to the Great Dirt Bed of the Caps. In an undergraduate research project, Clasby (2003) studied the footprint slabs and in particular these argillaceous beds. Pseudomorphs after halite occur in these. Insect remains include wings and elytra.

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SEDIMENTOLOGY:

The Salt Flat and the White Sand Beach

Coarse carbonate sand at the base of the Hard Slatt, Portland

On the Isle of Portland the Hard Slatt is a calcarenite limestone of rather less than a metre in thickness with cross bedding. It is partly oolitic, consisting of small ooids together with intraclasts and algal features. The ooids are not of marine Porland Stone type and not reworked from this lower formation. The carbonate allochems are particularly coarse-grained at the base, as shown in the photograph above. This basal layer, just above the salt-crust, consists of rather poorly-sorted, subangular to subrounded, carbonate grains. The deposit is unusually coarse for the Lower Purbeck lagoonal sediments, and may represent the nearest approach to "beach shingle" as the transgression washed carbonate material across the flooded sabkha. The main part of the Hard Slatt originated as a broad, low-profile (rather flat) storm beach of the lagoon (to the southeast). This beach was of white carbonate sand.

Mud-clasts with pseudomorphs after halite, Hard Slatt, Portland

A feature of the lower part of the bed is an abundance of flat mud-clasts which decrease in abundance upwards. Halite pseudomorphs within the mud-clasts show that they originated as desiccated mud sheets on a salty sabkha, like that which preserves the dinosaur footprints. These mud-clasts are also numerous in the equivalent bed on the mainland. The limestone shows cross-bedding, in some cases of herring-bone type, which is also a notable feature of the bed on the mainland. Its origin is probably quite rapid storm deposition of high-energy lagoonal, carbonate sediment. This must have been previously accumulated over a period of time and probably includes debris from the erosion of nearly contemporaneous sediments, including those of supratidal origin.

Salt-crust with dinosaur footprints

Moulds and casts of halite crystals from a salt crust, the Hard Slatt, Purbeck Formation, Bowers Quarry, Isle of Portland, Dorset, 2012

Human footprints in a modern salt-crust

Reconstruction of the Early Cretaceous salt-flat environment

Most of the tracks are associated with casts of small, concave-faced, cubes of halite at the original surface, with clay beneath. It would seem that in most cases the dinosaurs walked over salt-encrusted, firm but slightly plastic mud. Some comparision with modern salt-crusts, like those common in sabkhas and playa lakes, is shown above (although it is important to note that the climate was not as extreme as that of modern Middle Eastern deserts - note the presence of trees). The seasonal Mediterranean climate would imply that the prints were formed in the dryer summer season, or perhaps spring or autumn, but probably not in the winter. A rapid spread of carbonate sediment over the sun-dried mud would have preserved not only the indentations but also the impressions of the halite crystals. Although the carbonate shows rather high energy conditions, there was no major erosion just here but relatively rapid deposition associated with a transgression. The large mud-flakes show that the surface of dried mud was ripped up nearby. The extent of carbonate sand accumulation at this particular level in the Lower Purbecks in the region is interesting. It is located at the northwestern margin of the basin on the Lulworth and Portland Swells, but is not developed in the Durlston Bay basin facies. The position of the relatively coarse-grained carbonate accumulations in relation to the broad palaeogeography suggests that southeasterly storm winds were driving waves onto the shallows of the structural highs. Those footprints which originated above the salt layer, and generally without impact rims, were formed on the beaches or shoal of carbonate sand that thus developed at the lagoon margin.

For more on Purbeck sediments associated with dinosaur footprints see the Durlston Bay, Middle Purbeck webpage.

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FOOTPRINTS:

Introduction to Dinosaur Footprints

Many examples of dinosaur tracks and trackways are known around the world. The prints are usually in sandstone, limestone or hardened clay. The original track may be seen or an undertrack in which parallel laminae beneath are pushed down. The footprint or track may be seen as a mould or a cast or as both.

Dinosaur footprints - Theropod and Ornithopod types

Although there are many different types of dinosaur footprints, in very simple terms most, but not all, can be classified into one of three categories. These are: 1. Sauropod Footprints - large roundish prints like those of an elephant's foot and made by the large quadrupedal dinosaurs like Brachiosaurus or Diplodocus; 2. Ornithopod Footprints - tridactly (three-toed) prints of broad, rather flabby type made by the bipedal herbivorous dinosaurs like Iguanodon ; 3. Theropod Footprints - tridactlyl footprints of narrower type, with claws, made by the bipedal carnivorous dinosaurs. The first category - the Sauropod footprints, are quite distinctive. The diagram above shows the main differences between the Ornithopod and Theropod footprints. This is simplified and there are many variations of shape and complications of preservation which can make it difficult to place a track or trackway in one of these categories. This simple classification does not take into account some smaller quadrupeds. Apart from the description, in a full study the dimensions of the footprints must be measured, and, in addition, the pace between two prints and the stride between two prints of the same foot (i.e. two paces). Other variables include the angles between the toes, and the extent to which the prints turn out or turn in (pigeon-toed) in relation to the direction of the trackway. For more information on the study of dinosaur footprints particularly see Lockley (1991)

Notice in the images that follow that most of the prints (tracks) from this locality are relatively small for the Purbeck Formation and are not longer in the anterior-posterior direction than a man's foot. Some seem clearly to be of the broad Ornithopod type, although a small variety. Fortunately, one example, a small one reveals in cross-section that it is not an undertrack, but was made directly into a salt crust. Thus the broad shape is original and not due to some distortion at a depth beneath the true print. Since no print as large as that typical for an Iguanodon was seen an origin from smaller Ornithopod dinosaurs must be considered. Other tracks are narrower and may be of Theropod type. In one case there is some overlap of prints. Is this the result of one dinosaur following the trackway of another or has it been produced by some genus of quadrupedal dinosaurs. These apparently Theropod-type tracks are also small. It is possible that the semi-arid Lower Purbeck environment was less favourable for dinosaurs than the sub-humid Middle Purbeck environment. Examine the footprints, now, with these various ideas in mind.

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FOOTPRINTS:

Probable Ornithopod Tracks

Dinosaur footprints, Hard Slatt Bed, Hard Cockle Member, Lower Purbeck Formation, Isle of Portland

Dinosaur footprints with impact rims, Portland, Dorset

Dinosaur footprints -oblique view

Fairly close view, dinosaur footprint

The most impressive of the dinosaur footprints on Portland are those with well-defined impact rims. Examples are seen on a partially inverted slab here. These prints are present at or near the stratigraphical base of the Hard Slatt Bed and were impressed into a thin salt-crust over mud. The pseudomorphs or, more strictly, sediment casts, of halite are obvious. The impact rims were in some cases almost entirely of halite and in other cases involved mud. In one case, shown below, the impact rim was of a few millimetres of carbonate sand on salt-crust on mud. The features are clear in the photographs.

The footprints of this type have broad-toes and in this respect resemble Ornithopod prints. They are like small versions of "Iguanodon footprints". They are, however, about the same size as the Theropod-type prints shown further below. That is they are about 17 to 20 cm in length with a pace or step of about 0.8 cm. The impact rims are particularly well developed, and it is significant they may include a sand layer, as shown in a photograph below. This does mean that the toes appear wider than they really were. Thus although these prints seem to have originated from a broad-toed ornithopod, some degree of caution is needed in interpreting them.

Close view dinosaur footprints - allochems and pseudomorphs

Dinosaur footprint - halite between toes

Many of the footprints are impressed in a salt-crust, as shown by a surface of halite pseudomorphs or halite casts. These particular pseudomorphs are a surface type in which the downward protruding lower parts of the halite crystals have been filled with carbonate sediment. They are not where isolated halite crystals within a carbonate bed have been dissolved and the cavities filled with calcite. This latter type is common in the Soft Cockle dolomites and is of different origin. The pseudomorphs at the base of the Hard Slatt are in lateral contact, forming the preserved remains of the salt crust. Some halite has been squeezed up between the toes of the dinosaur footprints and preserved as pseudomorphs. There is clear evidence as shown by the photographs that the crust was deformed by dinosaurs walking over it.

dinosaur footprint and pseudomorphs after halite

Two dinosaur footprints, Hard Slatt, Isle of Portland

Here are some more with impact rims, shown with different type of surfaces and in different light conditions. In both cases the footprints are relatively small for dinosaurs, with a short step or pace. As in the other examples there is no impact rim at the rear of the footprint. This is evidence that the dinosaurs were semidigitigrade (partly on the toes) with some impression of metatarsals but not the heel. They were not fully digitigrade as is the horse.

Another three dinosaur footprints, Hard Slatt, Isle of Portland, Dorset

Three dinosaur footprints with possible slip towards a large depression, Hard Slatt, Isle of Portland

Shown in different light conditions, here are three prints of similar type and size, about 18cm in length, but with one them being offset and perhaps part of another trackway. Note the signs of slippage towards the large depression of contorted salt-crusts. The origin of the depression is not clear. It might have been a large sauropod print or it might have been produced by a dinosaur struggling in the mud and salt. If it already existed at the time when the small dinosaurs passed this way it might well have caused some minor sliding of one foot towards it. Notice incidently that there is some evidence of interference ripples and the environment had clearly had been very shallow water at one stage.

One natural print-cast enlarged showing mud in the impact rim

The first footprint seen in closer view. There are imperfect cubic casts of halite crystals, with concave faces, on the limestone surface (the under-surface). Notice how in this case mud has been pushed up into the impact rim or surrounding bulge. This is visible as some grey mudstone in the view from underneath. Notice the anterior-posterior ridges with parallel depressions developed in the central toe. The toe prints seem to end anteriorly in a rather indistinct rounded outlines, without any claw being obvious. The front of the footprint is not deep as is the print of a horse hoof when the horse is cantering. It is more the like the print of an animal that is just walking.

Development of multiple impact rim, dinosaur track, Hard Slatt, Isle of Portland

Details of sand rim, dinosaur track, Hard Slatt, Isle of Portland

Here are two more prints of broad-toed type. Shown more clearly in one photograph is the evidence of a thin carbonate sand impact rim. The presence of this shows that the salt crust was covered in this case by a thin sheet of carbonate sand and the animals were not walking directly on the salt. The evaporite was concealed under the sand layer. Notice the curved brittle-fractures. The dinosaur footprints were projecting downward as casts when compaction occurred. They would have impacted on the stratum beneath and consequently have been pushed upwards when the rock was in brittle-fracture condition.

Ornithopod testing the salt-crust before placing a foot firmly down?

These prints may give some indication of dinosaur behaviour. There seems to have been some testing of the the salt-crust by this Ornithopod, using the side toe and also the central toe. Presumably when satisfied that the creature would not sink deep it placed its foot fully on the crust. This was pushed down for a few centimetres and mud was squeezed up around the foot to form an impact rim. Seen from the underside of the Hard Slatt, this impact rim appears as a depression surrounding the footprint.

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Ornthipod-type Tracks of Smaller Size

Two of a set of three small dinosaur footprints, Hard Slatt, Isle of Portland Medium-sized and small footprints on the same slab, Hard Slatt, Isle of Portland Small and large dinosaur footprints

Medium-sized dinosaur footprint associated with a small print

Small dinosaur footprint associated with  medium-size print

Cross-section of a small type of dinosaur footprint, Hard Slatt, Isle of Portland

Some small prints of the same broad-toed type with impact rims are shown here. There are three small footprints in an approximate line and with regular spacing and two of these are shown here. On the far side of the slab is a larger footprint. There are impact rims and mud which was below the thin salt-crust has pushed up around the toes. This mud is now visible as grey mudstone. The directions of the larger and smaller tracks are not exactly the same, but both are in the same general direction and they are very close. Both have been impressed into the same salt crust. A cross-section of the first of the small footprints is shown above and this indicates that it has originated at the level shown and has not been pushed down from a higher layer. It is not an undertrack or underprint.

Dinosaur tracks, Hard Slatt, Isle of Portland

Cross-section through a dinosaur footprint, Hard Slatt, Isle of Portland

A cross-section of a larger footprint, already shown above, provides further confirmation that the tracks seen are true tracks and not undertracks formed several layers below the surface at which they originated. The cross-section is the natural break through the right-hand track of the left image. As noted above it is possible and, in fact, quite likely that a few mms of carbonate sand may separate the original surface from that which is seen, but the separation is small.

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DINOSAURS:

Ornithopod Iguanodon-type Track

Iguanodon-type footprint, Hard Slatt, Isle of Portland

A single large footprint of the broad, flabby Iguanodon type, like those well-known from the Middle Purbecks is present in the same slab as that containing the very small footprints. Compare this to the Middle Purbeck examples, shown below.

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DINOSAURS:

Theropod-type Footprints - without Impact Rims

Four narrow-toed dinosaur footprints with offset

Here are four small footprints of the narrow-toed type. They seem to be in two pairs with offset, and slight angular change of pointing direction. This is presumably being because they are both right and left foot prints. For scale the two white bands on the pen are at 5 cm. These prints are deeper at the toes and the heel is not properly developed.

Narrow-toed prints, wettened for visibility, Lower Purbeck Formation, Portland, Dorset

Shown above are narrow-toed footprints, wettened to increase visibility.

Three small dinosaur footprints in line on the upbulge slab

Narrow-toed dinosaur footprint in the Hard Slatt, Portland

Brittle-fracture upbulge with dinosaur footprint

Three photographs shown above, some taken in different light conditions, are all of the same slab. These prints are of narrow type without Impact Rims or marginal bulges. In particular the narrow-toed print at the front of the series seems almost theropod-like. The one at the rear has toes that are broader and flatter in appearance and although incomplete it is more like some of the others with broader toes. Clearly the prints from one animal can appear rather differently according to the behaviour of the mud and the details of preservation. Thus, interpretation has to be cautious.

Dinosaur footprint in the Hard Slatt at Mutton Cove

Dinosaur footprint in the Hard Slatt at Mutton Cove - labelled photograph

This example is not from the pile of slabs at the quarry, but is in situ in the west cliff of Portland . The Hard Slatt is well-exposed in a cliff-top ledge directly about the centre of Mutton Cove . It is just above an old cliff quarry in the Portland Stone. The bed here is thicker than at some other places and is divided into two parts by a central parting of shale. At the base of the upper part is what appears to be a cast of a tridactyl dinosaur footprint. The surface at the top of the shale, or mud, as it was, has been indented by three toes and a slight impression of a heel. There is no obvious impact rim and halite pseudomorphs were not seen at this level (although they occur in associated strata beneath the Hard Slatt). The significance of this footprint is that dinosaur footprints are not confined to one locality and not confined to the base of the Hard Slatt. The conditions were not only favourable for dinosaurs in this region during deposition of the Hard Slatt, but that the special sedimentary characteristics of this bed, particularly the content of coarse carbonate sand, were appropriate for preservation of footprints. It is hoped that more footprints may be found in this bed elsewhere, although they are certainly not common enough to be obvious at other localities. For more information on the Mutton Cove locality, see the Mutton Cove webpage and the undergraduate project report by Will (2003), which contains some petrographic information.

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DINOSAURS:

More Theropod-type Dinosaur Tracks

Footprints of theropod dinosaur type,  Hard Slatt, Isle of Portland

Footprints of theropod dinosaur type,  Hard Slatt, Isle of Portland - oblique view, unenhanced

Some footprints of theropod dinosaur type, unenhanced image, Hard Slatt, Isle of Portland

Some footprints of theropod dinosaur type, enhanced image, Hard Slatt, Isle of Portland

Superimposed footprints of theropod type

Details of overlapping dinosaur footprints, Hard Slatt, Isle of Portland

Two superimposed dinosaur footprints of theropod type

Two footprints of theropod type with computer tinting for clarity

Comparison of the Portland overlapping tracks with theropod tracks of Lockley

Clawed toe of theropod type, Hard Slatt, Isle of Portland, Dorset, UK

These tridactly footprints are rather larger than most at this locality. Two of the prints are partially overlapped by others. In addition to these four there are two indistinct and incomplete tracks in a different direction. These footprints differ from most of those on Portland. They have the narrow-toed characteristics of theropod dinosaurs as shown by the diagram above. Notice the impression of the pads on the feet and of claws in some cases. They might have been produced by two theropods (bipedal) following the same route. (Note that in the comparison diagram the drawings of the tracks of Lockley have been specifically positioned for comparison, and one has been cut, but the shapes of the prints have not been altered. See the original, complete diagram in the recommended book of Lockley (1991) for more information.)

Wider-spaced dinosaur tracks of possibly theropod type, Hard Slatt, Isle of Portland

These footprints seem to be of theropod type. They are spaced at about 95cm and only two are visible. If this was the pace (between right and left footprints) then this was made by a larger dinosaur than indicated by the other footprints. The lack of a third print between them seems to show that this was the pace and not the stride, which would, of course, have been twice as great. However, this is not proven because there is an indistinct mark to the right of the trackway, and it is just possible that the right foot impression has not been clearly made in the salt crust. A dinosaur might have been turning slightly left with more pressure on the left foot.

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DINOSAURS:

Ridges on Theropod Footprints

Ridges on dinosaur footprints

Some footprints show ridges on the base of the central toe. An example is shown above. These are in a antero-posterior direction and presumably form a sort of "tyre-tread". The particular footprint has some resemblance to the theropod-type discussed elsewhere on this webpage.

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DINOSAURS:

Anomalous Theropod Tracks with Faint or Missing Middle Toes

Two-toed tracks made with the middle claw raised

Last two tracks of the raised-claw type prints

Raised-claw type dinosaur footprints, close-up, Portland, Dorset

The middle (right) print of a theropod dinosaur with slightly raised claws, close-up

When the slabs were moved under the direction of Richard Edmonds on the 16 September 2003 some new and interesting tracks were revealed. Brushing a dirty slab revealed prints that have only two well-defined toe impressions, not three as is normal. There central toe print is light and indistinct in all three tracks, i.e. for both right and left feet. Favourable lighting conditions, however, does show a narrow central toe with a claw in two of the three prints. The dinosaur seemed to have had rather narrow toes and to have been walking plantigrade or even heel-down rather than in digitigrade manner, as was the case for most of the tracks. It was difficult to explain this.

The possibility of a Deinonychus or a similar dromaeosaur type of theropod dinosaur was initially considered. The second toe with the large claw of Deinonychus was held clear of the ground, and this seemed to me to provide some explanation. Thus it was thought at first that perhaps the tracks were produced by a dinosaur like Deinonychus or similar dromaeosaur. However, the raised "killer claw" of Deinonychus is the second toe of four toes. The first toe on the outside was small and would probably have made no impression. Considering just the three, it would have been the outside one with the large raised claw that should have resulted in the weakest marking, if any. This does not seem to correspond with the images. As is clear from the images here, it is the middle one of these three toes which is very narrow and shallowly impressed.

Theropod footprints with perhaps traces of the middle, partially-raised claw

Shown above is another image of the slab photographed from a different angle. This view seems to indicate traces of the termination of the middle claw. Notice again the 'flat-footed' stance of the dinosaur and also the weak impression of claw-marks of the side toes. These claws seem to have been raised to a limited extent.

A single footprint of a  dinosaur probably of a theropod with partially raised claws, Hard Slatt, Portland

Selectively enhanced image of theropod footprint with partially raised claws, Hard Slatt, Portland

Two photographs superimposed of the footprints with partially raised claws

The left-hand photograph (slightly oblique and therefore apparently narrowing the print) shows one of the prints in some detail. It is effectively unmodified, just having had some adjustment to gamma and sharpness overall. The middle image (also slightly oblique) has been enhanced but in a subjective manner after study of the left image. This image has the apparent area of the footprint shown in higher contrast than the surrounding which have been intentionally faded. If the the selection is correct (and you can judge for yourself) then the footprint is very bird-like with a narrow and light impression of the central claw. The right-hand image (near normal direction but not precise with regard to x-y ratio) has been constructed on the computer by superimposing one image on another of the same footprint. This method also seems to produce a bird-like footprint.

The origin of these footprints is at present a mystery. Is the absence or faintness of an impression of a central toe the result of a dromaeosaur-type sickle claw, raised above the surface, or is there some other explanation?

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DINOSAURS:

Imperfect Footprints - with with flat bases

Three dinosaur footprints in a track, Hard Slatt, Isle of Portland

Imperfect dinosaur footprint with halite pseudomorphs, Lower Purbeck Formation, Portland

These examples are rather poorly preserved and are almost flat at the base, with very limited depression. This bottom layer is the salt crust. They are probably being viewed at a few centimetres below the level at which they were made. The result is that they are less distinct and well-shaped and one of those on the left photograph is very broad, probably because of some oblique shearing. The upward injected mud, the impact rim is at the margin of this broad area. These probably represent a later passage of dinosaurs across a few centimetres thickness of carbonate sand above the salt and mud. The difference in type of preservation supports the view that the footprints are not all at one horizon.

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DINOSAURS:

Very broad-toed Dinosaur Footprint

Very broad-toed dinosaur footprint, Hard Slatt, Isle of Portland

Another view of the very broad-toed footprints, Hard Slatt, Portland

Here is a very broad-toed footprint with a circular print of some type in front of it. They might represent the tracks of pes (foot) and manus (hand) of a small quadrupedal dinosaur, but this is not confirmed and there could be some other explanation. There seems to be evidence of a varied assemblage of small dinosaurs of several different genera.

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DINOSAQURS:

Large Depression of Unknown Origin

Large depression in plastic sediment, base of Hard Slatt, Isle of Portland

An unexplained feature of the base of the Hard Slatt at the dinosaur footprint locality on the Isle of Portland is discussed here. An unusual and large depression of sediment with salt-crust that had been disturbed when still plastic was found. It in association with some small dinosaur footprints, three of which have been described above (notice that there is also a poorly-defined fourth example on the left). The depression is at least a metre in size, but the containing slab is broken and its limit on one side is not known. It has zigzag distortions that seem to be folds in the salt-crust. Some collapse or mechanical force was necessary for this type of deformation. It was formed before the brittle-fracture stage, shown by some structures on the slabs, and is not, therefore, the result of deep burial processes or late tectonism. The feature might be some early sedimentary structure such as a spring-pit, or, alternatively, like the small tracks, it may have resulted from dinosaur activity. A large sauropod footprint origin is possible, but there is no certain evidence for this. At present it remains a mystery.

Depressions in evaporite bed beneath the Hard Cockle Oolite, Worbarrow Tout, Dorset

Depressions in calcitised evaporites - possible footprints or inorganic structures

Depressions in gypsum beneath the Hard Cockle limestone, Worbarrow Tout

At Worbarrow Tout, on the Dorset mainland, depressions were found at about the same level, just under the Hard Cockle Oolite, the equivalent of the Hard Slatt. They are shown for comparison. These are of about the same size and are also impressed into evaporites, although in this case a bed of gypsum, since calcitised. These depressions also could be sedimentary structures or they might be sauropod footprints.

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TOOL MARKS:

Tool Marks and Unexplained Grooves etc.

Tool marks - oscillation marks in the mud, Hard Slatt, Lower Purbeck Formation, Isle of Portland

Tool marks, Hard Slatt, details

Tool marks, Hard Slatt, details of loop

Tool marks with burrow-like feature, Hard Slatt, Isle of Portland

The base of the Hard Slatt is characterised by well-developed halite casts, not only at the main site of the dinosaur footprints but elsewhere on the Isle of Portland. The main salt crust at the base in which the footprints are present contains some other features of interest at another locality. Here there are tool marks made by some pointed or blade-like object cutting into the mud. The tool marks are preserved as casts, relatively narrow but often with a flat base. They were grooves cut in the mud and then infilled with carbonate sand like that of the main part of the Hard Slatt. Some streaks and the manner in which one part of the mark crosses another suggests that the object moved overall from left to right. It is particularly interesting to note, though, that there are two set of oscillations recorded by this ancient blade. This is shown in the images above, where the groove swings back again in the reverse direction. The two reversal grooves (right to left) are of about the same length. At the loops the grooves seem deeper and oblique. In other places the grooving is not well-developed and all that is visible is a disturbance of the mud by the moving object.

A probable explanation of the origin of the markings follows but it is not by any means certain. The grooves have most likely been made by a floating object such as a log with a projecting branch, or a dead saurian or bird body with a hanging spine or beak. As noted, the shallow lagoon was subject to desiccation and development of salt crystals and dinosaur footprints. At other times, as during deposition of the main part of the Hard Slatt it was flooded by shallow saline or hypersaline water. During the course of such a flood some floating debris would have been transported landwards at the margin of the lagoon. Small waves would be expected to have been present, particularly since oscillation ripple marks are common in the Hard Slatt. Transport of the floating and mud-penetrating object landward by the flood 'tide' at the lagoon margin was likely but it was disturbed by small waves with back-wash. Large waves would have been unlikely in the shallow Purbeck lagoon and would have destroyed delicate structures. The deeper loops in the grooves might indicate small breaking waves. Shallow indentation or mere disturbance of the mud suggest that at these phases the object was lifted by the brine, presumably near the crest of a wave.

Since such delicate and sharp grooves were not likely to be preserved in good condition for long, it is likely that the sedimentation of the carbonate sand of the Hard Slatt took place almost immediately after the grooving. The sand would have been drifted in with this transgression. It is probable that the grooving and filling took place at the same time as the dinosaur footprints were preserved as casts by the carbonate sand.

These markings warrant further study because they may reveal more information about the conditions during this transgression by the lagoon that brought in coarser carbonate sediment at the start of deposition of the Hard Cockle Member. The traces are in a loose block but it might be possible to establish some directional data, using structural features in the block for orientation.

Sinuous groove in salt crust - tail mark or inorganic? Hard Slatt, Isle of Portland

Location of sinuous groove in relation to dinosaur tracks, Hard Slatt, Isle of Portland

This zigzag mark is present in the slab (at the main dinosaur footprint site) which has three broad-toed tracks and with a very large irregular depression. If this mark had been found with a direction corresponding to the footprints it would have been interpreted as a tail mark with some confidence. Unfortunately it trends at right angles to the small tracks. It is close to the large impression which might be of sauropod origin and could be due to some fracturing of the salt crust affected by the impact, or of some inorganic origin. Thus its origin is unknown but it is shown here in case some future finds shed light on it.

Possible claw-marks, Lower Purbeck Formation, Isle of Portland

These small curved indentations resembling claw-marks were found in a relatively thin (a few cm thick) slab of white, pelletoidal, lagoonal limestone. This is amongst the debris of finer material dumped alongside the large slabs with the dinosaur footprints on the Isle of Portland. The probable reptile skin impression came from this pile of debris. The thinner-bedded limestone here is likely to be from above the Hard Slatt horizon, because some thin beds of limestone are present there, and the material seen does not resemble the Shingle which lies beneath. No thorough investigation of its source has been made though. The origin of these marks is unknown, but they might possibly be from the claws of turtles, mammals or lizards or the beaks of birds. Clearly recognisable footprints have not been found in the slab. There is some indication that the marks are paired with a separation of about 1.5 cm to 2 cm. There are three possible pairs present.

Hemispherical marks in a former salt-crusts

These markings were found in a replaced salt crust that is probably the base of the Hard Slatt, at a more northern locality. They are not typical footprints because they do have a distinctive shape with toes and are isolated and not parts of trackways. They have been calcium sulphate nodules like those of modern sabkhas but such nodules normally form beneath the surface and not at the surface. One of them has an impact rim which suggests that it results from some object pressing down into the salt-crust and underlying mud. Although found in blocks, not in situ, which are at present about 200 metres apart, and in slightly different sediment, they are similar in shape and size. There is no obvious explanation as to their origin. Could they have been coprolites?

Reptile scratch marks or vegetation impressions? Middle Purbeck Formation, Durlston Bay

These problematical markings are not from the Portland dinosaur site but are from the Middle Purbeck Formation of Durlston Bay and are shown for comparison. They might possibly be scratch marks made by swimming or floating reptiles because of some limited similarity to marks figured by McAllister (1991, fig. 37.1 - fig. 37.3, p. 345) in the Cretaceous Dakota Formation of Kansas. However, they are much more elongate and do not have clear features which prove them to be of reptilian origin. Another possibility is that they are impressions of some plant debris, perhaps of cycadophytes. They are shown here, merely as another puzzling trace fossil of the Purbeck Formation which, just might be of reptilian origin. The block of limestone (in the possession of Ian West) is ex situ from the debris of the upper part of the Middle Purbeck Formation (Upper Building Stones up to Chief Beef Member). It is of lagoonal shell limestone, a biosparrudite with Neomiodon shells, of a type common in the beach material of Durlston Bay. It is a rather distinctive, blue-hearted, somewhat irregular limestone. It was encountered in landslide debris at the Zigzag path in the centre of Durlston Bay, many years ago. Should the block prove to be of any significance it is likely that further study would enable the limestone to be matched to that of one of the biosparrudite beds and the exact horizon identified.

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UPBULGE:

Small Upbulge Structures of the Hard Slatt

A brittle-fracture upbulge, Hard Slatt, Portland

Brittle-fracture upbulges, Hard Slatt, Portland

Brittle-fracture upbulge with dinosaur footprint

These circular and oval features occur at the base of the Hard Slatt at the dinosaur footprint slabs in association with the dinosaur footprints. The footprints, however, show no brittle-fracture cracks, whereas the circular or oval objects are marked out by such cracks and in some cases parallel pairs of cracks. The footprints are casts of downward impressions, but the brittle-fracture structures are upward (although they are seen now in overturned blocks and thus appear superficially as depressions). Because these strange features show brittle fracture presumably they are much later in origin than the footprints. The bed has presumably become partly or completely lithified before these were formed. The features represent bulges made by something that was resistant when the bed was compressed under burial and collapsed to a small extent around the circular or oval plates of a resistant substance. The most likely cause were large disc-shaped mud-clasts, but there are other possibilities.

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SEDIMENTARY STRUCTURES ASSOCIATED:

Ripple Marks etc

Oscillation ripple marks characterise the top of the Hard Slatt at most localities on Portland. They are also present on the mainland. The Hard Slatt, the bed from which the blocks containing dinosaur footprints have come, is well-exposed at the cliff top above Mutton Cove . There is also a dinosaur footprint here. At Mutton Cove the ripple marks on the top are particularly conspicuous.

Ripple marks from the top of the Hard Slatt, dinosaur site, Isle of Portland

Oscillation ripple marks in Hard Slatt, cliff-top ledge, Mutton Cove, Dorset

Hard Cockle Limestone with oscillation ripples at Durdle Door, Dorset

Cliff-top ledge of Hard Slatt, Mutton Cove

Oscillation ripple marks are present on the slabs of Hard Slatt limestone at the dinosaur footprint site. These slabs are associated with those which contain dinosaur footprints and seem to show the top of the bed of limestone. They show some features of oscillation ripples. A very shallow-water environment, like that of a beach, is implied. Some truncation of the ripple marks shows that the water was only a couple of centimetres deep before burial and preservation.

Similar ripple marks are present on the top surface of the Hard Slatt in situ in the cliff at Mutton Cove . Ripple marks also occur at partings within the bed.

Thick Hard Slatt in cliff-top ledge, Mutton Cove

Shingle-Hard Slatt junction with ripple cross-bedding

Vee-shaped structures in the Hard Slatt, Portland

General view of the Hard Slatt Bed above Mutton Cove is shown. Ripple cross-lamination is abundant in this bed and there are many rip-up clasts of clay. Ripple cross-lamination occurs close to the junction of the Shingle and the Hard Slatt, in the cliffs south of Mutton Cove

These vee-shaped markings were found on a slab of the Hard Slatt which has fallen to the undercliff in the climbing area, south of Mutton Cove, near the topple. They are probably two intersecting sets of ripple-marks at different levels.

It is clear that the Hard Slatt is an extremely shallow water deposit from bottom to top. The interesting petrography with abundant intraclasts and reworked ooids shows relatively high energy conditions for the lagoonal Purbeck Formation. Halite pseudomorphs and blue-green microbial ('algal') remains indicate high salinities. It seems to have formed as a type of lagoon-beach of white carbonate sand, but was very flat and extensive with little sign of development of any large bank or berm.

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PROBLEMATICA:

The Tabner Find - Reptile Skin Impression or Sedimentary Structure?

Problematica - anomalous markings in Purbeck limestone, dinosaur site, Isle of Portland

Whorls in the anomalous structure in Purbeck limestone

Problematica in Purbeck limestone, dinosaur footprint site, imw specimen

Problematica from the Purbecks, another block

Prolematica - enhanced and modified image

Anomalous markings compared to alligator skin

In loose blocks at the site of the dinosaur footprints some anomalous markings have been found by Stuart Tabner. These are present in thin-bedded Purbeck limestone where there is contact with a lamina of black shale. The facies is typical lagoonal Lower Purbeck (usually hypersaline to some extent) but fish remains in the form of a vertebra are associated. Another vertebra has been found in associated blocks.

The origin of these impressions is a matter of much interest. Early discoveries suggested that they seem to cover an area of at least 30 cm square, and perhaps more, as a thin continuous flat sheet. They have small whorls and roughly parallel rib-like features. There is no recognisable bone, other than an attached fish vertebra, and no significant quantity of carbonized plant debris is preserved. The present writer's first thought was that they represent an impression of reptile skin in the soft carbonate mud at the margin of the shallow lagoon. Comparison was made with the skin of an alligator, as shown above, and there seems to be some similarity but there has been no definate confirmation of a crocodilian origin. The markings do not include clearly-defined scales such as have been seen in dinosaur skin impressions, although Ankylosaur skin has been mentioned as a possibility. They have not been recognised as of plant, fish, burrowing ichnofossil or sedimentary-structure origin. The markings are not those of a calcified stromatolite or microbial mat; they are just an impression in pelletal carbonate silt. That they are possibly the remains of some thin organic mat has not been completely eliminated but nothing similar has yet been noticed.

It is perhaps worth mentioning that the rib-like features and the whorls seem to have fairly constant characteristics, although there is some variation. The rib-like features are mainly parallel, so there is a lineation to the structure. It gives an impression of having been made by some well-organised organic sheet or film. The whorls are rather cone-like with very thin darker laminae descending into them at low angles. No large tears, breaks or folds have been seen. The limestone is very ripple-laminated and mostly unfossiliferous like several of the Purbeck limestones of the Hard Cockle Members of Portland. The way-up has not yet been determined.

Problematica - double Y markings

Between the whorls there are double-Y shaped structures, almost like girder bracings on a bridge. A photograph of these is shown above, with some colour enhancement. Examination of the main specimen photographs higher up will reveal several examples of these markings. Closer study of the whorls suggests that they are layered in a shallow conical manner with two or three parallel 'dishes'.

Further searching by a group including Stuart Tabner, Debbie Tabner and Linda in October 2003 revealed more of the markings in several blocks found in different parts of the pile of Purbeck debris. This suggests that the markings cover an appreciable area, perhaps to be measured in metres. No folds, tears or special structures were found. Unfortunately, this seems to indicate a sedimentary structure origin, because it would be surprising for a skin impression to be so even and so extensive. The markings have been located at a very finely laminated, almost varved, argillaceous limestone layer at the margin of a 10 cm thick bed of Purbeck lagoonal limestone. This may be the "Coombefield Thin Limestone Bed" above the Hard Slatt. (more information will be added).

Shed skin of a living gecko lizard

Comparison of fossil markings in Purbeck limestone and modern reptile (gecko) skin

The markings resemble to some extent those in the shed skin (left image) of a gecko lizard, which my wife keeps. The comparison is shown in the image on the right, although, of course the gecko is small and the markings are small. The gecko skin is from the underbelly. The features are not identical, of course, but there is much resemblance. There is, indeed, sufficient similarity, in the view of the author, to support the view, which came initially from illustrations of crocodiles, that these fossil markings really are an impression of reptilian skin. If the markings are roughly in proportion, the fossil skin would have been of a creature at least an order of magnitude larger than a small pet gecko. Reptiles of this size were common in the Purbeck environment.

Confirmation of a reptilian and probably dinosaur origin comes from an illustration in Edmonds (1979) of an impression of Iguanodon skin found with 30 Iguanodon skeletons from the famous Cretaceous Bernissart locality in Belgium. The discoveries were made in 1878. The illustration is not of good quality and is not reproduced for copyright reasons (it is hoped to obtain a good copy in due course). The skin has ridges rather like those in Stuart Tabner's specimens, although not so straight. It has the Y-shaped junctions. The scale is not given. Edmonds wrote " According to experts the pattern of markings could mean only one thing: it was an impression of the iguanodon's skin. From this we can assum that the animal was not so much scaly as covered by a skin with regular little bumps." No typical Iguanodon footprint has yet been found at the Portland locality but the small broad prints are effectively smaller versions of Iguanodon - type prints and may well have been made by a related ornithopod. The origin of the Tabner impression is, of course, not firmly proven but it is very likely that it really is reptilian skin and may well be of dinosaur origin.

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SEDIMENTARY STRUCTURES:

Small Channels or Gutter Casts

Small channels with lag concentrates of ostracods and gastropods, Portland, Dorset

Ostracod and minute gastropod concentrate in a small channel, Portland, Dorset

Gutter marks in the upper striped beds, Jet Wyke, Staithes

Some small channel-like features, resembling gutter casts, occur in some slabs of Purbeck lagoonal limestone at the dinosaur footprint site. These are not from the Hard Slatt with the footprints, but from a different and thinner bed of limestone, probably from a short distance above. At the base of the small curved channels are lag concentrates of ostracod valves and minute gastropods. Although these are small objects they are coarser than the general sediment of the bed which is probably pelletoidal limestone.

Right: Compare these to gutter marks or gutter casts at Staithes, Yorkshire, in the Middle Lias. There the small channels are in a marine deposits and may have been formed in subtidal sea conditions. The Purbeck example is from a very shallow and restricted lagoon. If further work shows that these are true gutter marks then the possibility should be considered of such sedimentary structures having been formed in very shallow environments such as the "intertidal" zone.

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QUARRY SECTIONS

The Hard Slatt (Dinosaur Bed) in Some Quarry Sections

There are several quarry sections which include the Hard Slatt or dinosaur footprint bed. Footprints have been found in situ in a cliff exposure at Mutton Cove, referred to above, and have also been found in a loose block on the West Cliffs. They may well be found in place in more of the quarries sooner or later. The Hard Slatt is well seen and accessible at Windmill Quarry (North Perryfield); it is present at the main Perryfield Quarry.

A dinosaur footprint in the base of the Hard Slatt, Lower Purbeck Formation, Bowers Quarry, Isle of Portland, Dorset, 2012

Here is a single footprint from the Hard Slatt at at Bowers Quarry, which I noticed in 2012. This footprint is of Ornithopod type, and was found at the same halite crust horizon in one of the many loose, blocks of the Hard Slatt present in this quarry. Footprints are very rare at that locality though. The Hard Slatt in which the print was found is equivalent to part of the Hard Cockle Member of the Purbeck Formation. Thus it is not surprising that the "cockles", Protocardia purbeckensis are present within the fill of the footprint, probably in association with the usual lagoonal ooids that characterise this bed.

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PURBECK FOOTPRINTS:

Middle Purbeck Footprints for Comparison

Reconstruction of an Iguanodon dinosaur making footprints in the carbonate sand of the Purbeck lagoon in early Cretaceous times

Dinosaur footprint from Middle Purbeck limestone, Swanage

Dinosaur footprint in the Intermarine Member of the Middle Purbeck Formation, Worbarrow Bay, Dorset, old photograph

Dinosaur footprints in the Intermarine Member at Worbarrow Tout, 1978

A broad-toed Dinosaur footprint in the Intermarine Member at Worbarrow Tout, 1978

Dinosaur footprints have been found from time to time in the quarries inland to the west of Swanage. They are present mostly in the Intermarine Member of the Middle Purbeck Formation, particularly the Roach Bed and adjacent strata. These footprints, unlike those in the Hard Slatt, are in biosparrudite limestone composed of lagoonal bivalve shells such as Neomiodon. Some of the footprints are of Iguanodont type. These broad-toed footprints resemble the broad-toed examples from the Hard Slatt but they are much larger. An example is shown here.

Some old photographs (1978), above, show dinosaur footprints in a dipping slab of biosparrudite of the Intermarine Member of the Middle Purbeck Formation at Worbarrow Tout. Mud has been placed in the footprints to give them emphasis for the photographs. These footprints are still visible but rather worn and degraded now.

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Footnote:
"An enormous three-toed track was imprinted in the soft mud before us. The creature, whatever it was, had crossed the swamp and passed on into the forest. We all stopped to examine the monstrous spoor.... 'Iguanodons,' said Summerlee. 'You'll find their footmarks all over the Hastings sands in Kent, and in Sussex. The south of England was alive with them where there was plenty of good lush green-stuff to keep them going'. " (Arthur Conan Doyle, The Lost World, 1912)
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Dinosaur trackways were found in Suttle's Quarry at Herston near Swanage, received much publicity in 1962 when they were discovered. There several newspaper articles about them (see under Anonymous). They were discussed briefly by Charig and Newman (1962) and a photograph has been shown in a book on dinosaurs by Charig. The trackways seem to be of the narrow-toed type.

The discovery of dinosaur footprints at Lock's Quarry, Acton, Swanage in 1967

Dinosaur tracks found at Lock's Quarry in 1967

Footprints shown above were found in a quarry at Acton, near Langton Matravers, west of Swanage, Dorset in 1967. After more excavation about 31 prints of theropod type were found in two trackways which intersected twice (Delair, 1982). The anterior-posterior measurement of the footprints (not the pace or stride) averaged 28 cm in one track and 34 cm in the other. Measurements of the spacings of the prints were given by Delair in a plan of the footprint site. The footprints occurred in the Pink Bed of the Roach of the Intermarine Member. Part of the trackways were acquired by the Royal Scottish Museum, Edinburgh and have been put on display.

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PURBECK FOOTPRINTS - Middle

Purbeck Dinosaur Footprints, with a Long Toe, in Durlston Bay

(This is an extract from the Durlston Bay - central part - webpage.)

Dinosaur footprint with a long toe, in bed DB 118, Intermarine Member, Durlston Bay, Dorset, England

Dinosaur footpint with a long toe, loose block on the beach from the Purbeck Formation, Durlston Bay, Dorset, England

A speculative interpretation of a dinosaur footprint from the Lower Cretaceous Purbeck Formation, Durlston Bay, Dorset

The footprints shown above come from the central part of Durlston Bay. There is more information on dinosaur footprints in the Middle Purbeck strata of Durlston Bay in the Durlston Bay, Middle Purbeck webpage. Two photographs are shown above of natural casts in limestone of prints with usually long central toes. The impressions of claws can be seen. As is the case of the dinosaur footprints in the Purbeck strata of the Isle of Portland the central claw is partially turned to the side in one of these prints. One of the dinosaur footprints is in situ in the Lias bed DB 118 of the Intermarine Member and this has been described by Nunn (1990). The other one is on the beach and has chisel holes in the block suggesting that an unsuccessful attempt has been made to remove it from the shore. The two prints are very similar but no detailed comparison has been made of the prints or of the limestone in which they occur. Thus it is not known at present whether they are from the same bed. This is quite possible as they are not far from each other.

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SUPPLEMENT:

Dinosaur Footprint from the Wealden Ashdown Sands, Hastings

A dinosaur footprint with partial impression of the hock, Ashdown Sands, Pett Level, Hastings, East Sussex, photograph courtesy of James Codd

Shown for comparision is a dinosaur footprint from the Ashdown Sands of Hastings (photograph kindly sent to me by James Codd). This seems to be of Ornithopod (Iguanodon) type. It is interesting in suggesting that the hock was down and at a very low angle. This does not agree well with modern reconstructions that show Iguanodons with the hock raised. Old kangeroo-type reconstructions do, in fact, place the hind cannons at low angles. Of course there may be some special explanation for a single footprint with these characteristics.

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ACKNOWLEDGEMENTS

I am particularly grateful to Richards Edmonds, Earth Science Manager of Jurassic Coast, the Dorset World Heritage Coast organisation of Dorset County Council and also to Ben Murray the Manager of the Hanson PLC quarry for showing me the footprints and arranging visits and meetings. Richard has encouraged and organised study of the footprints and Ben has drawn attention them from time to time and seen to their protection within the quarry site. There has been valuable discussion and various field trips with Paul Ensom, Justin Delair, the late Michael House, Justin Delair, Caroline Clasby, Stuart Tabner, Debbie Tabner, Shiela Alderton, Linda and many members of the Dorset Geologists' Association Group and the Open University Geological Society and this is much appreciated. It is particularly good of Stuart and Debbie Tabner to allow me to provide illustrations of the strange markings which Stuart discovered at the dinosaur site. I am grateful to James Codd for kind permission to reproduce a photograph of a dinosaur footprint from the Ashdown Sands. I am particularly grateful to Paul Ensom for discussion on these footprints and for a pdf copy of his paper with Justin Delair on the subject of these dinosaur footprints. I thank Chris Robson of Royal Holloway, University of London for drawing my attention to new literature on dinosaur footprints. The running of this website on the University server by the Faculty of Natural and Environmental Science of Southampton University is very much appreciated.

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OTHER BIBLIOGRAPHIES, References and Internet Links

Go to Bibliography and References on Geology of the Isle of Portland.. Most papers referred to in this webpage are in this bibliography.

Go to Bibliography of the Purbeck Formation. This in alphabetical order by author and not by topic.

Go to Bibliography of the Purbeck Formation, Topics. . This is split into topics in alphabetical order.

Go to Select Bibliography of Dinosaurs in the Purbeck Formation (in preparation) .

Go to Middle Purbecks of Durlston Bay. This also refers to Purbeck dinosaur footprints.

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SELECT BIBLIOGRAPHY AND REFERENCES

(see also Bibliographies of the Purbeck Formation.)


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Anonymous . 1962a. Dinosaur passed this way. Evening Echo, Bournemouth , January 17 1962. "In a quarry high above Swanage the footprints (seen above) of an ancient dinosaur have been unearthed. It is believed to the first complete track of such footprints found. The foot-wide prints were made by a giant Iguanodon lizard over a hundred million years ago..." continues. Also article entitled: 'Echo' man follows the 100,000,000 year trail. Also photographs of the footprints in Suttle's Quarry.

Anonymous. 1962b. The slow march of a Purbeck Iguanodon. New Scientist, No. 271, 25 January 1962. p. 186 in Notes and Comments. [But see Charig and Newman (1962) , below, who described three trackways and consider that they were not necessarily made by an Iguanodon and consider that a carnivorous bipedal dinosaur may have been responsible.

Anonymous. 1963. New discovery of dinosaur prints in Swanage Quarry. Evening Echo, Bournemouth, Tuesday, 25 June 1963. "Sensational discovery made on Saturday by a team of experts from the British Museum investigating the dinosaur tracks in a Swanage quarry is that a series of smaller prints running with the tracks are made by the front legs of the massive creatures. Mr B.H. Newman of the Fossil Department of the British Museum, in charge of operations, claims that this supports his theory that the creatures walked on all fours, not upright, as commonly supposed in the past. " I regard this as conclusive proof of a theory that I have canvassed for many years," he told a reporter in the quarry on Saturday afternoon. The team had spent that day lifting and packing on to a lorry the last of the pieces of stone bearing dinosaur footprints. He told how earlier that day he had been painting in the last numbers on fragmented pieces of stone, so that they can be reassembled at the Museum, when he noticed that small indentations near the larger footprints recurred frequently along the trackway. So he examined them very closely, washed out the small cavity and checked the dimensions of each one. They were three toed and symmetrical and he is satisfied that they were made by the front paws of the pre-historic creatures. .. As reported previously the iguanodon tracks found in the quarry of Messrs J. and E. W. Suttle near the Municipal Caravan Site on Swanage quarries land are the longest continuous stretch of double prints ever found in this country. ..The original discovery 17 months ago was of a single line of 13 footprints running north to south. Six of these prints have been taken up to London. "This of course is a herbivorous creature and the nature of the foot much more fleshy, much less birdlike than the other prints, which were bigger and perhaps more importantly set. These ran transversely from the others, being east to west and were made by a megalosaurus. This was a "fairly large carnivorous bipedal dinosaur" and the prints were one foot by one foot (30cm) and in parts over an inch (2.5 cm) deep. .. Pointing out the front footprints he said that they were made by one curved digit and two smaller digits, he added "and they occur so regularly in association with the hind prints that they cannot be dissociated. He wished to make it clear that though earlier reports referred, correctly, to 150 yards (about 150 metres) total length of trackway discovered, not all was taken to the British Museum. About 75 ft ( 23 m) of the side by side tracks had gone and 35 ft (11 m) of the single track. .. Mr. Newman paid tribute to Mr John Suttle and his younger brother Mr Wilf Suttle who had given tremendous help and made the operation possible. This must have been at great financial cost to themselves and their only reward is the knowledge that it is due to them that this important discovery - the most significant of its kind in Europe - will be preserved for ever in the national collection." [There are other newspaper cutting of 1962 and 1963 discussing the excavation and study of these footprints. Other person involved were Mr E.F. Oppe of Worth Matravers, Mr P.A. Brown of Corfe Castle, Mr J.B. Delair, and Dr A.J. Charig of the British Museum, who has published photographs of the trackway.]

Anonymous. 1981. (Title not known but on dinosaur footprints from Townsend Road, Swanage.) Daily Telegraph, Newspaper, 12 September, 1981. [More than 100 dinosaur footprints discovered on a plot of land at Swanage, Dorset, five weeks ago, were moved to the County Museum at Dorchester yesterday. Most of the prints were made by the three-toed Megalosaurus 150 million years ago.]

Anonymous. 1987. Footprints of 'new' dinosaur found in quarry [Sunnydown Farm Quarry, near Swanage]. Evening Echo, Bournemouth (newspaper), 28 April 1987. Extracts: " A series of footprints found in a small quarry near Swanage, which were made by a type of quadrupedal dinosaur, have been recovered from .. the Purbeck Beds. The first clue to the unusual nature of the discovery was the extraction of a very large, 76 cm long and 61 cm wide cast of an apparently four-toed footprint (photograph was provided). .. With the agreement and help of the owners Mr. and Mrs. R. Notley, Dorset County Museum, owned and run by the Dorset Natural History and Archaeological Society, has so far lifted an area of limestone and revealed many more footprints on the site at Sunnydown Farm Quarry. These have truncated and therefore much shorter, front foot casts just in front of those made by the back foot. Not only are there at least three tracks made by quadrupedal dinosaurs, but also a large number of tridactly footprints criss-crossing the site. ..So far sieving and painstaking sorting of residues has yielded many hundreds of minute crocodile teeth, a small teeth of carnivorous dinosaurs, a fragment of a tooth belonging to an herbivorous dinosaur, numerous fragments of lizard jaws and the teeth of a flying reptile (pterosaur)... Still more exciting and quite unexpected is the discovery of mammal teeth. These are very small, some less than half a millimetre across. They represent the first major finds of such remains sicne first half of the last century when S.H. Beckles opened his famous mammal pit above Durlston Bay, near Swanage." [For more information on Sunnydown Farm Quarry and the discoveries see the work of Paul Ensom of the Natural History Museum, London. ]
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Delair , J.B. 1982. Multiple dinosaur trackways from the Isle of Purbeck. Proceedings of the Dorset Natural History and Archaeological Society, vol. 102 for 1980, 65-67. [ Brief discussion of dinosaur footprints at three sites in the Isle of Purbeck. These are of theropod type from the Middle Purbeck of Lock's Quarry, Langton Matravers (although listed as Acton on some photographs), of Iguanodont type from Worbarrow Tout and wrongly recorded as Lower Purbeck but actually Middle Purbeck above the Cinder Bed, and of Iguanodont type from a quarry at Queensground, Acton, near Swanage. The Lock's Quarry set were brought to Delair's attention by the late Mr E. Oppe. The footprints occurred in the Pink Bed of the Roach of the Intermarine Member. Part of the trackways were acquired by the Royal Scottish Museum, Edinburgh and were put on display. Two trackways were found with a total of about 31 prints and the tracks crossed over at two points. The anterior-posterior measurement of individual prints averaged 28 cm in one track and 34 cm in the other. Measurements of the spacings of the footprints are given in a plan of the site.

Delair, J.B. 1985. Some little known Jurassic Ichthyosaurs from Dorset. Proceedings of the Dorset Natural History and Archaeological Society, 107: 127-134.

Delair, J.B. and Brown, P.A. 1975. Worbarrow Bay Footprints. Proceedings of the Dorset Natural History and Archaeological Society, vol. 96 for 1974, 14-16.
Extract (most of the paper):
"In 1888, Mansel-Pleydell (5, p.36) mentioned the occurrence of footpints with dissociated Iguanodon remains in the Wealden formation at Worbarrow Bay. This appears to be the only published record of reptilian footprints of any age at Worbarrow. [In fact, though, these footprints had already been reported briefly reported by West et al. and had been well-known for a long time and regularly pointed out on field trips. As a result of such a trip they are also shown in Kirkaldy, J.F. 1970. Fossil in Colour. Blandford Press, see p. 48.]
Although the present writers have failed to locate Mansel-Pleydell's specimens (which, of course, may actually have never been collected), it appears certain that they were of the three-toed or tridactyle variety since, in Mansel-Pleydell's day, only footprints of that kind were assigned to Iguanodon. More recently the essentially identical tridactyle dinosaurian footprints I present at certain subjacent Purbeck horizons have been separated into two distinct groups, ascribed respectively to Iguanodont and Megalosaurian dinosaurs (7, figs. 1 and 2). It is unknown, therefore, whether Mansel-Pleydell's Worbarrow Bay footprints were of Iguanodont or Megalosaurian type, even though we may be sure that they were of dinosaurian origin.
There are, however, no reasons to doubt that Mansel-Pleydell's Worbarrow specimens really were from Wealdon [sic] beds (which outcrop on the northern side of the bay), since elsewhere he specifically mentions two footprint-bearing sandstones in the Wealden formation at Swanage Bay (6, p.117), and clearly distinguished the Wealden from the Purbeck beds at those localities. The footprint-bearing sandstones of Swanage Bay had, in fact, been recorded as far back as 1862 (2, p.446), and presumably it was to the specimens found at that early date that Mansel-Pleydell referred. There appears to be no published record of exactly when the Worbarrow Bay footprints were discovered and examined, although their discovery obviously antedated 1888.
Somewhat oblique confirmation of the general accuracy of Mansel-Pleydell's dating of these early footprint discoveries is contained in the obituary of the late Frank Raw (died 2nd September, 1961), which mentions the discovery many years later of at least one further tridactyle footprint in the Wealden strata at Swanage Bay (8, p.159). The recent discovery, therefore, of several trackways composed of tridactyle footprints in the basal Purbeck beds at Worbarrow Bay (fig. l) constitutes a new record for footprints of that age in Dorset, and is a find of considerable interest.
The present specimens (uncollected) were examined in situ during late September 1973 by the writers, shortly after one of them (PAB) had learned of their existence by chance. As photography of the specimens was not possible (due principally to their awkward location and to indifferent lighting conditions at the time) the arrangement of the footprints, relative one to another, is shown in fig.2.
With the exception of a single additional footprint found on a block obviously fallen from some higher level, and collected by PAB, all the footprints occur as impressions on the upper surface of a black-speckled limestone tilted downwards towards the north at an angle of approximately 55° and towards the west at an angle of about 25°. Stratigraphically, the position of this bed is difficult to correlate precisely with those of other Purbeck sections in this district, but appears to equate with bed no:6 in Arkell's summary of the basal Purbeck series on the east side of "Worbarrow Tout" (1, pp. 301-2). This correlation, however, is provisional only as the precise age of the Purbeck beds in the Worbarrow Bay area, and especially those north of the "Tout", has recently been queried (4, p.567).
The single detached specimen mentioned above appears to have fallen from the Cypris Freestones or from the Broken Bed underlying them (1, pp.301-2, see beds 12 and 13 in the published section).
As shown in fig.2, the footprints form three separate trackways, all aligned in a general north-easterly direction. Measured between the two out digits, the width of each specimen, which in some cases is rather indistinctly defined, is approximately 7 inches. That of the detached footprint from the higher horizon is approximately 8 inches, and, like those of the trackways is of Iguanodont type.
The stratigraphical position of these footprints is of particular interest, inasmuch that it apparently lies in or near the basal Purbeck series [This is in error - the footprints are from above the Cinder Bed!], and occurs much lower down than the main and, to date, much more productive footprint-bearing horizons the Middle Purbeck series of the Swanage district further east (3, see fig. 2) [not true]. The reported existence of tridactyle reptilian, footprints in the lower Purbecks has, however, been known for many years (6, p.122) [?]. Of additional interest is the fact that even at the present low [sic] horizon, footprints of a general Iguanodont type occur .. at least in the Worbarrow Bay region .. in relative abundance, a circumstance which has hitherto passed unnoticed [it has not!].
Our best thanks are due to the army authorities at Lulworth Camp for permission to visit Worbarrow Bay which, with the neighbouring area, lies within the military testing grounds.
APPENDIX Further to the stratigraphical distribution of dinosaur footprints in the Dorset Purbeck formation summarized by Delair and Lander in 1973 (3, fig.2), it is, perhaps, appropriate here to add the following supplementary details that have come to light since the publication of that paper, since, together with the Worbarrow Bay discovery detailed above, they constitute notable additions to the record.
At least one well preserved cast of a typical Iguanodont footprint has recently been recovered from the "Soft Burr" bed in 'Marble Quarry' north of Langton-Matravers, while several additional similar casts have been collected from the "Roach" stone at 'Worth Gate Quarry', near Acton.
All these trace-fossils are now owned by Mr David Sole of Langton-Matravers, to whom we are indebted for the opportunity of examining them.
On March 3rd, 1967, Mr Geoffrey Tyers, from Nottingham, found another Iguanodont footprint in a limestone block on the foreshore at Peveril Point, Swanage. Almost certainly the block had fallen from an Upper Purbeck horizon (as yet undetermined) in the adjacent cliffs. This specimen, which is now owned by a Mr E. Fuller, is of considerable interest in the footprints of Upper Purbeck age are encountered only rarely. Indeed, only Mansel-Pleydell has recorded the definite occurrence of dinosaurian footprints from the Upper Purbeck beds of Dorset (6, p.122), even though it seems that the specimens upon which that record was based are now lost.
Our grateful thanks are due to Prof. W.A.S. Sarjeant of Saskatchewan University, Calgary, for bringing this latter discovery to our attention.
P.A. Brown, Corfe Castle, Dorset.
J.B. Delair, Wootton, Berkshire.
1st October, 1973 (Revised, 21st February, 1974)."
[With fig. 1, location map of Worbarrow Bay and Tout and fig. 2, a drawing of the footprints. Also with 8 references.]

Delair, J.B. and Lander, A.B. 1973. A short history of the discovery of reptilian footprints in the Purbeck Beds of Dorset with notes on their stratigraphical distribution. Proceedings of the Dorset Natural History and Archaeological Society, vol. 94 for 1972, 17-20.

Delair.J. B. and Sarjeant, W.A.S. 1985. History and Bibliography of the Study of Fossil Vertebrate Footprints in the British Isles: Supplement 1973-1983. Palaeogeography, Palaeoclimatology, Palaeoecology, 49: 123-160.
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Ensom - Paul Ensom, notable author of many papers and notes regarding the Purbeck Formation of Dorset (and other Dorset topics, including Lias, Middle Jurassic and Kimmeridge Clay). Geological editor of the Proceedings of the Dorset Natural History and Archaeological Society.

Ensom , P.C. 1982. Dinosaur footprints at 19 Townsend Road, Swanage. Proceedings of the Dorset Natural History and Archaeological Society, 103, p. 141. By Paul Ensom.

Ensom, P.C. 1982. Ichnites sp. from Worbarrow Tout, near West Lulworth. Proceedings of the Dorset Natural History and Archaeological Society, 103, p. 141.

Ensom, P.C. 1983. Ichnites sp. from the Chief Beef Beds and Broken Shell Limestone, Durlston Beds, Purbeck Limestone Formation, Durlston Bay, Swanage. Proceedings of the Dorset Natural History and Archaeological Society, 104, p. 201.

Ensom, P.C. 1983. Correction to: 'Multiple trackways from the Isle of Purbeck', J.B. Delair. In Proceedings of the Dorset Natural History and Archaeological Society, 102, 1982. Proceedings of the Dorset Natural History and Archaeological Society, 104, 201-202.

Ensom, P.C. 1984. Ichnites spp. in Durlston Bay and on Worbarrow Tout. Proceedings of the Dorset Natural History and Archaeological Society, 105, 166-167.

Ensom, P.C. 1984. Purbeckopus pentadactylus Delair Proceedings of the Dorset Natural History and Archaeological Society, 105, 166.

Ensom, P.C. l985. An annotated section of the Purbeck Limestone Formation at Worbarrow Tout, Dorset. Proceedings of Dorset Natural History and Archaeological Society, 106, 87-91. [Useful log compatible with that of Clements for Durlston Bay]

Ensom, P.C. l985. A correction and additions to the distribution of Ichnitesin the Purbeck Limestone Formation of Worbarrow Tout and Durlston Bay. Proceedings of Dorset Natural History and Archaeological Society, 106, 166-167.

Ensom, P.C. 1986. Ichnites sp. from the Upper Cypris Clays and Shales Member (Purbeck Limestone Formation) near Harman's Cross, Dorset. Proceedings of Dorset Natural History and Archaeological Society, 107, 183.

Ensom, P.C. 1987. A remarkable new vertebrate site in the Purbeck Limestone Formation on the Isle of Purbeck. Proceedings of Dorset Natural History and Archaeological Society, 108, 205-206. [See also Correction to ..A remarkable new vertebrate site ...; in Proceeding of Dorset Natural History and Archaeological Society for 1989, published 1990, p. 133. Correlation with bed WB112 should have read WB117. ]

Ensom, P.C., 1987, [Dinosaur tracks in Dorset. Anon, but based almost verbatim on text supplied by PCE]. Geology Today, 3, pp.182-3.

Ensom, P.C. 1987. Notes on Ichnites spp. in the Purbeck Limestone Formation, Dorset. Proceedings of Dorset Natural History and Archaeological Society, 108, 206.

Ensom, P.C. 1988. Excavations at Sunnydown Farm, Langton Matravers, Dorset: Amphibians discovered in the Purbeck Limestone Formation. Proceedings of Dorset Natural History Archaeological Society, 109, 148-150. [Sauropod footprints, salamanders, multituberculate mammals. Iguanodon footprints. Cherty Freshwater Member. Also see paper in Palaeontology giving full description of mammals.]

Ensom, P.C., 1989, Sunnydown Farm sauropod footprint site. Proceedings of the Dorset Natural History & Archaeological Society, 110, pp.167-8.*

Ensom, P.C. 1994. A new vertebrate trackway from the Intermarine Member, Purbeck Limestone Formation, Dorset. Proceedings of Dorset Natural History and Archaeological Society, 115, 183-184.

Ensom, P.C., 1999, Vertebrate trace fossils from the Purbeck Limestone Group of southern England. In: Milner, A. [Editor]. Abstracts: Life and Environments in Purbeck Times, 19th - 22nd March 1999: pp.20-21.

Ensom, P.C. 2002. Vertebrate trace fossils in the Purbeck Limestone Group of Southern England. Pp. 203-220 in: Milner, A.R. and Batten, D.J. (Editors) 2002. Life and environments in Purbeck times. Special Papers in Palaeontology, No. 68, Palaeontological Association, London, 268pp. Abstract: The Purbeck Limestone Group (late Jurassic-early Cretaceous) contains a rich vertebrate trace fossil fauna. Research on this fauna has been almost entirely concerned with dinosaur tracks. By contrast, the feeding traces and coprolites, which are occasionally abundant, have received little attention. The implications of some recent papers, including those where ichnotaxa are assigned, are considered along with the stratigraphic and geographic distribution of reptilian tracks. A plan of the principal footprint horizon at Townsend Road, Swanage, is presented and the more unusual aspects of the site illustrated. An appendix gives a comprehensive listing of published and manuscript accounts dealing with footprints from these strata. Some of the neglected feeding traces and coprolites are described and illustrated for the first time.

Ensom, P. 2009. A dinosaur track from the Wealden Group (Lower Cretaceous), Worbarrow Bay, Dorset, southern England. Proceedings of the Dorset Natural History and Archaeological Society, Natural History Reports, pp. 233-234.
Extract:

"While leading a field trip for the Open University Geological Society (South West Branch) in October 2008, the cast of a single, indifferently preserved, apparently tridactyl track was found on a fallen and partially buried block of fine-grained, pale sandstone at the foot of a cliff at Worbarrow Bay (NGR SY 86949 80313). In addition a second track is hinted at with a single putative digit preserved on one edge. .... The conclusion reached was that Stewart's Bed no. 7 was probably the source, the in situ bed exhibiting some structures similar to the fallen block. ..."

Ensom, P.C. and Delair, J.B. 2008. Dinosaur tracks from the Lower Purbeck strata of Portland, Dorset, southern England. Geoscience in Southern England [Proceedings of the Ussher Society], 111, 309-325.. [This is on the footprints shown above].
Dinosaur tracks from strata below the Cherty Freshwater Member, Lulworth Formation, Purbeck Limestone Group, of Dorset had not been recorded formally until 2002 when Professor Michael House published a preliminary note, in the Proceedings of the Dorset Natural History and Archaeological Society. He flagged the 2001 discovery of a number of blocks of the ‘Thick Slatt’, Hard Cockle Member, with casts of dinosaur tracks preserved on their lower surfaces, in a quarry on the Isle of Portland. New light is shed on the source of the tracks, and the history of their discovery is documented. The methods employed to record them are described. The traces are placed in their stratigraphic and palaeoenvironmental settings.
In this paper, how the tracks were made is described, and most importantly it is concluded that they are preserved as transmitted casts. Three distinct types of tridactyl track attributable to bipedal dinosaurs are recognized, as well as isolated tracks which are interpreted as belonging to quadrupedal dinosaurs. Evidence is presented to support the interpretation that one of the tracks assigned to a quadrupedal dinosaur was produced by a sauropod. Despite their apparent differences, it is suggested that the majority of the tridactyl tracks were left by one species of dinosaur which was almost certainly herbivorous and lived in groups. One trackway may have been made by a carnivorous dinosaur.


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Francis , J. 1996. Paddling in the Portlandian: a new record of dinosaur footprints from the Purbeck/Portland transition, Portland. Palaeontological Association Newsletterr, No. 32. Abstracts for the 1996 Annual Meeting. By Professor Jane Francis.
One paragraph only (as below) on page xv of the Abstracts volume. "A new set of dinosaur footprints has been discovered on the Isle of Portland on an exposed bedding surface in a disused quarry. The footprints are shallow impressions of small (up to 14 cm in length broad three-toed prints, very similar to those made by bipedal tridactly ornithopods such as Iguanodon . They do not appear to form a distinct trackway, more of a meandering stroll assemblage. The footprints occur in the upper surface of a transitional bed between the underlying marine shelly oolites of the Portland Stone Formation and overlying palaeosols and algal limestones of the Purbeck Lulworth Formation. This bed represents a change from high energy carbonate shelf facies to shallower, lower energy conditions prior to the onset of terrestrial soils/hypersaline lagoon environments. This is the lowest stratigraphical occurrence of footprints known in the Purbeck Group, since previously recorded footprints occur much higher in the Middle Purbeck Durlston Formation. These footprints show that ornithopod dinosaurs paddled happily in the shallows of the Portlandian seas in the Mediterranean climate that prevailed at that time." End of Abstract. By Jane Francis, Department of Earth Sciences, University of Leeds, Leeds, LS2 9JT. [The location is believed to be a small abandoned quarry of Portland Stone with basal Purbeck Caps and Dirt Beds above Freshwater Bay, on the east cliffs of Portland, map reference 691702, but nothing is very obvious there at present. The bed is the Transition Bed, a thin and laminated pelletoidal limestone, characterised in many places by a fauna of small lagoonal gastropods, such as Hydrobia as moulds and with some foraminifera visible in thin-section. It is fused directly to the top of the Portland Freestone which is characterised by the shells of large marine molluscs. IMW]
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Gillette , D.D. and Lockley, M.G. 1991 (first paper edition - 1991, hardback first edition - 1989). Dinosaur Tracks and Traces. Cambridge University Press, Cambridge. 454pp. ISBN 0-521-36354-3 hardback, ISBN 0-521-40788-5 paperback. [This is a volume of 51 papers by various authors which originated at a conference: First International Symposium on Dinosaur Tracks and Traces. It was held at Albuquerque, New Mexico, at the New Mexico Museum of Natural History on May 23-24, 1986. Topics in the volume include: Introduction; Historical Perspectives; Locomotion and Behavior; Eggs and Nests; Paleoecological, Palaeoenvironmental and Regional Synthesis; Biostratigraphy; Experimentation and Functional Morphology; Site Reports; Systematic Ichnology; Conservation and Preservation. It contains a large quantity of information with details and references to previous work. It is recommended for further study.]
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Hunter , S. 1967. Pardon, old thing, but your slip is still showing. Glasgow Herald, Newspaper, 13 March 1967, p. 8. "Iguanodon did stagger 120 million years ago and this morning geologists at Glasgow University have the scoop of the story of where he slipped. At the Hunterian museum they to-day uncovered a 21 feet (6.4 m) limestone track where a dinosaur walked - the first indoor exhibition of any such track in Britain. .. Dorset quarrymen found the prints [in Suttle's Quarry in 1962]. The two-ton track was then lifted from the Middle Purbeck beds and crated in pieces to Glasgow. .. He (she?) swivelled rather at the hips and put the feet down almost in line. This kind of mannequin movement involves some rotation of the foot at the ankle and would produce a smudged impression on a slippery surface. So the blurred fourth footprint of the Hunterian slab marks the spot where Iguanodon skidded in the mud." [Article written in 'popular' style by Samuel Hunter. The footprints are probably not of an Iguanodon. See Charig and Newman (1962) and other articles listed here.
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Lockley , M. 1991. Tracking Dinosaurs: A New Look at an Ancient World. Cambridge University Press, Cambridge. 238pp. ISBN 0-521-39463-5 hardback, ISBN 0-521-42598-0. By Martin Lockley, University of Colorado at Denver. Extract from Preface: "The main objective of this book is to convey to the lay reader the substantial contribution that tracks make to our understanding of the Age of Dinosaurs. The professional reader should also benefit from the book because it deals with many new discoveries and synthesises much of what is known." [This is a very good book for understanding the basis of the study of dinosaur footprints and clearly explains terms like stride, step, pace, pace-angulation, plantigrade, digitigrade, true-tracks, undertracks, impact rims etc. and has many illustrations of tracks made by different genera of dinosaurs. It is a useful introduction to the subject.]
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Mansel-Pleydell , J.C. 1888. Fossil Reptiles of Dorset, Proceedings of Dorset Natural History and Antiquarian Field Club, vol. 9. pp. 1-40.

Mansel-Pleydell, J.C. 1896. On the Footprints of a Dinosaur (Iguanodon?), from the Purbeck Beds of Swanage, Proceedings of Dorset Natural History and Antiquarian Field Club, vol. 17, pp. 115-122.
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Martill , D.M. and Naish, D. (Eds.) 2001. Dinosaurs of the Isle of Wight. Palaeontological Association, Field Guides to Fossils: Number 10. The Palaeontological Association, London. 433pp. ISBN 0 901702722. Edited by David M. Martill and Darren Naish, technical editing by David J. Batten, photography by Robert Loveridge and computer generated artwork by Stig Walsh. Price of paperback in 2003 - £16. Contents: Acknowledgements; Preface; 1. Introduction by Martill, D.M., Naish, D. and Hutt, S.; 2. The Geology of the Isle of Wight by Martill, D.M. and Naish, D.; 3. The Global Significance of the Isle of Wight Dinosaurs by Martill, D.M. and Naish, D.; 4. Taphonomy and Preservation by Martill, D. ; 5. Ornithopod Dinosaurs by Naish, D. and Martill, D.M.; 6. Boneheaded and Horned Dinosaurs by Naish, D. and Martill, D.M.; 7. Armoured Dinosaurs: Thyreophorans by Naish, D. and Martill, D.M.; 8. Saurischian Dinosaurs 1: Sauropods by Naish, D. and Martill, D.M.; 9. Saurischian Dinosaurs: Theropods by Naish, D., Hutt, S. and Martill, D.M.; 10. Dinosaur Trace Fossils: Footprints, Coprolites and Gastroliths by Martill, D.M. and Naish, D.; 11. Pterosaurs by Howse, C.B., Milner, A.R. and Martill, D.M.; 12. An Aid to the Easy Identification of the Commoner Wealden Dinosaur Bones by Martill, D.M. and Naish, D.; 13. A Dinosaur Trail by Martill, D.; Glossary of Terms; References, Appendix; Further Reading; Useful Information; Systematic Index. [The book is mostly in monochrome with numerous photographs and diagrams, but there are 16 colour plates in the central part. It contains a mass of information and is exceptionally good value for money. In addition to its main use regarding Wealden strata it is relevant to the Purbeck Formation of Dorset, because it discusses the dinosaur contents of a higher part of the Lower Cretaceous in the same general region, and some similar dinosaurs might be expected to have been present in the Purbeck (Berriasian). There is specific reference to Purbeck dinosaurs and Purbeck dinosaur footprints in places, as for example on pages 134 and 135 where Echinodon and Nuthetes are discussed. The chapter on dinosaur footprints, pages 310 et seq. is clearly of significance regarding Purbeck footprints and these are mentioned briefly (particularly of Iguanodon).]
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McAllister , J.A. 1991. Dakota Formation tracks from Kansas: implications for the recognition of tetrapod subaqueous traces. Paper 37, pp. 343-351 in: Gillette, D.D. and Lockley, M.G. 1991 (first paper edition - 1991, hardback first edition - 1989). Dinosaur Tracks and Traces. Cambridge University Press, Cambridge. 454pp. ISBN 0-521-36354-3 hardback, ISBN 0-521-40788-5 paperback. Abstract: Criteria for the recognition of tetrapod trails are compiled from the literature and are illustrated by one example of footmarks from the Dakota Formation [Cretaceous] of Kansas. The Kansas footmarks are most easily recognised by criteria which indicate tracemaker bouyancy. Such foomarks are characterised primarily by posterior overhangs and reflectures of the individual digit impressions; and secondarily by striations and claw marks along their length and the often incomplete nature of the trails. These swim footmarks would be expected to grade into subaqueous traces formed by more typical terrestrial propulsion and demonstrate less bouyancy as the water becomes shallow, and disappear as the tracemaker becomes fully bouyant in deeper water and digits no longer reach the substrate.
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Milan , J. 2006. Variations in the morphology of emu (Dromaius novaehollandiae) tracks reflecting differences in walking pattern and substrate consistency: ichnotaxonomic implications. Palaeontology, vol. 49, issue 2, pp. 405-420. By Jesper Milan, University of Copenhagen.
Abstract:
Fossil footprints appear in a variety of preservational states, each revealing a different morphology that can give rise to misidentification and misinterpretations. Comparative ichnological work was conducted using living emus (Dromaius novaehollandiae). It was clearly demonstrated that the morphological variation that occurred in footprints of the same animal, walking in the same manner, was caused by variation in substrate consistency. Dry sand substrates are unlikely to preserve any anatomical details of the foot, whereas damp sand or mud of firm consistency preserves a high level of anatomical detail. The finest anatomical details, such as skin impressions, are only preserved in firm mud or clay. In semi-fluid to fluid mud the track walls collapse, destroying the shape of the footprint. Increased speed of progression affects the shape of the footprint dramatically as the distal ends of the digits become more deeply impressed in the substrate during acceleration. Plantigrade stance adopted by the emu while feeding produces highly elongated footprints. Applying these observations to the study of fossil footprints demonstrates that great care should be paid to the original sedimentary conditions at the time of track making, as well as to the stance and gait of the trackmaker.

Milan, J. and Bromley, R.G. 2006. True tracks, undertracks and eroded tracks, experimental work with tetrapod tracks in laboratory and field. Palaeogeography, Palaeoclimatology, Palaeoecology, vol. 231, (2006), pp. 253-264.
Abstract:
To be able to distinguish between true tracks, undertracks and tracks altered by erosion is of great importance in tetrapod track ichnotaxonomy. This paper reports three experimental approaches to the study of undertracks using the footprints of an emu (Dromaius novaehollandiae). Experiment 1 describes successive horizontal sections down through a plaster cast of an emu footprint emplaced in soft mud, revealing a steady downward decrease in the area of the track, particularly the length. This is the result of the movements of the trackmaking limb during impact, forward swing of the body and final kick-off. Experiments 2 and 3 describe vertical sections cut through footprints emplaced in packages of layered, coloured cement, admixed with water to produce different consistencies, firm and semi-fluid. After hardening, the cement block was serial-sectioned vertically, and removal of a lightly cemented layer gave access to two undertrack bedding-plane views. Successive undertracks downward show an increase in horizontal dimensions and decrease in vertical topography of the structure, representing gradual degradation of the track anatomy with depth. In experiment 3, the true track at the tracking surface was deformed by collapse and flow of the substrate after withdrawal of the foot. In this case the undertracks that were formed in layers subjacent to the foot reproduced the morphology of the foot more faithfully than did the true track.
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Nunn , J.F. 1990. A new tridactyl footprint impression in Durlston Bay, Swanage. Proceedings of the Dorset Natural History Archaeological Society, 111, 133-134.
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Oppe , E.F.
(Mr. Oppe was a keen collector of fossil footprints in the early 1960s when they were just beginning to obtain publicity in the press. He lived at Worth Matravers and knew the local quarrymen. He drew attention to the unusual non- tridactlyl track in his possession - Purbeckopus pentadactylus and to the trackway discoveries at Suttle's Quarry and elsewhere. At a later stage he assisted the vertebrate palaeontologist Justin Delair and discussed footprints with me when I was at Worth Matravers from time to time.)

Oppe, E.F. MS scrapbook. Dorset County Museum, Natural History Manuscript Collection, document no. 68. This has not been seen by the webpage author, but is referred to by Ensom (2002) on: Vertebrate trace fossils in the Purbeck Limestone Group of southern England, . It is presumably from about 1960 and may contain more detail in relation to dinosaur footprint records in Oppe and West (1962) below.

Oppe, E.F. 1965. Isle of Purbeck: Sunny Spaces and Dinosaur Traces. Published by the author, 31pp. A short guide book by Ernest F. Oppe of Peaky, Worth Matravers, Swanage, Dorset. Including historical notes (reprinted) on Corfe Castle by the late Dr G. Dru Drury, F.S.A. Original price - single 2 shillings and 6 pence a copy; and for co-operative spread 10 copies for £1. With a foreword by F. W. Anderson and with an acknowledgement to Justin Delair. [This booklet discusses the Suttle's Quarry dinosaur trackway, Hayward's trackway and others. There are photographs of both Suttle's and Hayward's trackways. Suttle's Quarry was an old quarry reopened on the heights above Herston Cross. The footprints here have been discussed elsewhere (See Charig and other publications) and they indicate a pace of 106cm. There are photographs of both Suttle's and Hayward's trackway. Ten prints in a single line with only small lateral displacement of left and right feet were seen at Hayward's quarry. The pace is referred to as 97 cm., with another figures from separate measurements giving 99 cm. Individual footprints were of about 20 cm length (in the direction of the trackway).

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Oppe, E.F and West, I.M. 1962. The Significance of Fossil Footprints in the Purbeck Beds of Dorset. 4 pp. Old unpublished draft for a short paper that was never submitted, but lists the records to 1962. It was based on a privately circulated manuscript of 1960 by Oppe (Some Latter-Day Fossil Finds in the Isle of Purbeck, Mesozoic Era) which was summarised with additions and modifications by Ian West in 1962 and retained as a type-script, 4pp.
Abstract : Footprints, mostly ascribed to the Iguanodon, have long been known to occur in the Purbeck Beds. They are significant from a stratigraphic point of view, in indicating very shallow water conditions or subaerial exposure and also the proximity of vegetated land. Several new occurrences are noted and a list of previous records compiled.
Introduction: Periodically, records of fossil footprints in the Purbeck Beds of Dorset have been published (e.g. Mansel-Pleydell, 1896; Calkin, 1933; Suttle et al., 1962). These are usually tridactyl and ascribed to the Iguanodon but will not be considered here fully from a palaeontological point of view. The frequency of occurrences has been greatly underestimated; not only are many specimens lost in the course of quarrying operations, but others are seen yet remain unrecorded . ... It is particularly unfortunate that there is no record, in that they possess a stratigraphical significance and are an indicator of water depth. It seems unlikely that these footprints could have formed in other than very shallow water or subaerial conditions. Furthermore, the depth of impression, usually 2 and a half (6.4 cm) to 3 inches (7.6 cm), suggests that the beds containing these were partially consolidated, while the attribution of the prints to a large herbivorous dinosaur at least suggests the presence of a vegetated land at no great distance. A lateral facies change to that of a "dirt bed" or fossil soil might well be expected at the appropriate horizon.
Particular Features of Some Unrecorded Prints: With the exception of a rare five-digit footprint [Oppe's specimen of Purbeckopus pentadactylus - although actually with four toes according to Ensom, 2002], all specimens are tridactly. The length from heel to toe is unreliable, owing to the possible dragging of the feet, but it not greatly different from the width, usually about 12 inches (30 cm) or less. An exceptional width of 18 inches (46 cm) is sometimes found but this track is clearly a larger than the actual foot which made the impression... Purbeck quarrymen often come across footprints and in one case remember the recurrence of a mishapen foot in a particular trackway. In another case a trackway was said to form a complete circle. It is also generally known in the quarries that one footprint shows in two or three superimposed slabs, the displacement of the original partially consolidated bed continuing down for up to 6 inches (15cm) [See Lockley, 1991 on "undertracks"].. Thus one overlying cast, which is usually lost in quarrying, is found above several superimposed imprints each with a corresponding bulge on their lower surfaces.
Footprint horizons in Dorset. (As known to Mr Oppe in 1960 with some additions by Ian West in 1962):
Haywards Quarry, No. 7, Spyways, Langton Matravers - Roach - three prints of 9 inches and two smaller. All point west;
Locks Quarry, Acton, Langton Matravers - Roach (Pink Bed) - two prints 11 inches apart, 18 inches but probably the lowest slab of a superimposed series, in Mr Oppe's collection;
Cobbs Quarry, Acton, Langton Matravers - Roach - two prints each 9 inches, about 9 inches apart;
Cobbs Quarry - Roach - medium sized, at Worth Matravers.
Cobbs Quarry - Roach - 18 inch cast in the County Museum, Dorchester;
Swanage area, exact location unknown - Laning Vein - preserved at Swanage, medium size, one natural cast; Langton Matravers area, exact location unknown - bed unknown - good prints supplied to collectors in Southall and Brighton.
Landers Quarry, Gallows Gore, Langton Matravers - Roach - five prints preserved at Corfe Castle, 8 to 12 inches;
Unknown locality - preserved at Worth Matravers; Unknown locality - preserved at Worth Matravers;
Langton Matravers area - bed unknown - 8 inches, preserved at Bristol;
Langton area - bed unknown - on display in the shop window of the Purbeck Press, Swanage;
Swanage - Corbula Beds - Mansel-Pleydell, 1896 p. 115 et seq., print and cast (natural) with "fucoidal" marking [trace-fossils - burrows - may be Thalassinoides];
Peveril Point, Swanage, bottom of rugged path to the beach - Unio Bed of the Upper Purbeck - Ord, 1914, p. 342 - "distinct footprints of a large Iguanodon which are rapidly being worn away by modern feet, and unfortunately the slab is too large for removal."
Suttle's Quarry, Herston, Swanage - Roach (Pink Bed) - Anonymous (1962), Suttle et al. (1962), Charig and Newman (1962), Swaine etc. - At least 25 feet (7.6 m) of uninterupted trackways consisting of two parallel rows of prints two feet (61 cm) apart. Width of individual prints 1 foot (30 cm), length of "stride" 2 feet (60 cm) [unreliable? Is this actually the pace or step not the full stride with the same foot?], trackway heads in the direction 240 degrees (to the southwest). Another single trackway mentioned by Swaine (1962) is present.
Locality unknown - Roach, above and also in Pink Bed - Calkin (1933), 14 prints in two trackways like those of Suttle's Quarry. Prints 11 inches (28 cm) wide.
Swanage or Langton Matravers area, exact location unknown - Roach Bed - Benfield (1948, p. 32), 3 footprints found by Jimmy Chinchin and his brother, in an underground mine, purchased by a museum for 20 pounds.
Conclusions: Tridactyl footprints have frequently been discovered in the Middle and Upper Purbeck Bed, especially in the much-quarried Roach. At least three of the above-listed occurrences are however from the Durlston Bay cliff section, and it is clear that the stratigraphical distribution is not entirely controlled by the presence of well-exposed surfaces at the quarried horizons... Thus, in spite of numerous exposures and a vast degree of quarrying on Portland, the absence of well-authenticated tridactyl footprints in the Lower Purbeck Beds of Dorset requires explanationMansel-Pleydell (1862, p. 122) records, though, that he had been told by a Mr. Hardy that footprints had been seen in these beds. Although it is possible that examples might be found at suitable horizons in the future [we are now in the future, in the 21st century, and they have been found, and indeed only at certain horizons. See webpage on Dinosaur Footprints on Portland. ], there is a general absence in spite of mudcracks indicating suitable conditions for their preservation. Probably the highly saline and rather arid environment that persisted through most of the Lower Purbeck Beds, commencing in the Caps ( (West, 1961) was unfavourable to large dinosaurs [note those footprints since found on Portland are small]. The general absence of dinosaur bones in these also tends to confirm this view.
References: Anonymous (1962); Benfield (1948); Calkin (1933), Mansel-Pleydell (1896), Ord (1914), Suttle, Brown, Oppe and White (1962), Swaine (1962), West (1961). [References are not given in full here because they are listed in this bibiography. These notes were written more than 40 years ago and since then many more finds have been made. For more information see Ensom (2002) on: Vertebrate trace fossils in the Purbeck Limestone Group of southern England, , and particularly his "Bibliography of vertebrate tracks from the Purbeck Limestone Group of Dorset," pp. 217-220. ]


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Robson, C. 2009. How do experimental studies help us to interpret fossil footprints and trackways. G13800 Course, Literature Report, Department of Earth Sciences, Royal Holloway, University of London, 16pp. By Chris Robson.
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Suttle , E.W., Brown, P.A., Oppe, E.F. and White, H.J. 1962. Track of a Dinosaur: Iguanodon - type, biped, 3-toed. Unpublished hand-out sheet circulated in Dorset in 1962. Copy in the possession of Ian West. Extracts: "13 imprints of each foot extending uninterruptedly westward for a distance of 25-26 feet (7.6 m to 7.9 m) exposed on the quarried surface of Pink Bed in Purbeck Roach, Nov-Dec. 1961. At Messrs J. and E.W. Suttle's Swanage quarry (The quarry is on high ground above the top end of Hillsea Road, Herston, Swanage, Dorset). [Parallel tracks are shown diagrammatically with footprints heading to 254 degrees, i.e. WSW.] .. The footprints, naturally varying in state, are shewn stylised as being perfectly isolated and wholly familiar in local character, i.e. medium-size, 3-digit footprints of which numerous specimens are preserved, commonly from the Purbeck Roach. .. Pink Bed is the bottom layer of several slabs or slats which form Purbeck Roach to a typical thickness of up to 2 feet (0.6 m). Pink Bed stone varies from 5 inches (13 cm) to almost none or 'dirt', and in this and other instances registers the bottom, lowest, compression of the mud originally trodden [i.e. an undertrack, beneath and parallel to a track or impression in a higher lamina or layer]." By E.W. Suttle, Langton Matravers; P. Anthony Brown, Corfe Castle; E.F. Oppe, Worth Matravers; and H. John White, Swanage. [A local record of the Suttle's Quarry discovery, important in drawing attention to the find. The initial interpretation of the two trackways as a single one made with left and right feet of a dinosaur was later corrected by Charig and Newman (1962) to a theory of two nearly parallel trackways. A third trackway was also found. Charig also questioned the Iguandon interpretation.]
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Swaine , J. 1962. Iguanodon footprints. New Scientist, No. 276, 1st March 1962.
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West , I.M. 1979a. Sedimentary Environments and Diagenesis of Purbeck Strata (Upper Jurassic - Lower Cretaceous) of Dorset, U.K. Unpublished Ph.D. Thesis, Southampton University, 181 p. Abstract: Twelve papers, notes and a contribution to a book, all either published or accepted for publication, constitute this thesis. All parts of the classic, shallow-water, schizohaline Purbeck Formation of the type area are discussed but emphasis is on Lower Purbeck evaporites. Diagenesis of these involved much conversion of initial small lenticular crystals of gypsum to anhydrite with net-texture. The anhydrite was extensively replaced by calcite and celestite in the Broken Beds, a tectonic evaporite breccia at the base of the Purbecks. Evaporites were almost completely lost in solution from this breccia leaving characteristic relics of "vanished evaporites". Elsewhere, in the more argillaceous parts of the formation the sulphate remains, mainly as porphyrotopic secondary gypsum. Nodules and enterolithic veins are abundant in both the calcium sulphate and in the replacements. The similarity to those in Holocene sabkhas of the Trucial Coast (Shearman, 1966) suggested an origin on supratidal sabkhas, but there is a lack of desert sediments and instead the evaporites are interbedded with forest soils. Analogous Carboniferous evaporites show evidence of sabkha origins but no sign of desert conditions [West, Brandon and Smith, 1968. A tidal flat evaporitic facies in the Visean of Ireland. Journal of Sedimentary Petrology, 38, 1079-1093.]. New evidence has come from sabkhas in Northern Egypt where gypsum nodules develop in partly vegetated environment, dry but not excessively so, and supports other evidence for a semi-arid origin for the Lower Purbeck evaporites [West, Ali and Hilmy. 1979. Primary gypsum nodules in a modern sabkha on the Mediterranean coast of Egypt. Geology, 7, 354-358.]. The relatively dry climate was temporary and facies of higher parts of the Purbecks seem to result from sub-humid conditions. Throughout the formation lagoonal, 'intertidal' and supratidal deposits can be recognised but in the Middle and Upper Purbecks the lagoonal sediments have abundant brackish shelly faunas and, there, 'tidal-flat' deposits consist of shell-sand with dinosaur footprints but usually without evaporites. Progressively the proportion of land-derived clastics such as kaolinite and quartz sand increases as the continental Wealden is approached and final Purbeck sediments contain debris eroded from the underlying Portland Stone Formation, then uplifted at the western margin of the basin.

West, I.M. 1988 Notes on some Purbeck sediments associated with the dinosaur footprints at Sunnydown Farm, near Langton Matravers, Dorset. Proceedings of Dorset Natural History and Archaeological Society, 109, 153-154.

West I.M. and El-Shahat, A. 1985. Dinosaur footprints and early cementation of Purbeck bivalve beds. Proceedings of Dorset Natural History and Archaeological Society, 106, 169-170.

West, I.M., Shearman, D.J. and Pugh, M.E. 1969. Whitsun Field Meeting in the Weymouth Area, 1966. Proceedings of the Geologists' Association, 80, 331-340. [Portland, section of Perryfield Quarry etc]
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Zhang, J. Lib, D., Li, M., Lockley, M.G. and Baib, Z. 2006. Diverse dinosaur-, pterosaur-, and bird track assemblages from the Hakou Formation, Lower Cretaceous of Gansu Province, northwest China. Cretaceous Research, Vol. 27, Issue 1, February 2006, pp. 44-45. By Jianping Zhang, Daqing Li, Minglu Lia, Martin G. Lockley, and Z. Baib. Available online 10 February 2006.
Abstract: Diverse and well-preserved assemblages of dinosaur (theropod, sauropod and ornithopod), pterosaur, and bird tracks from the Hekou Formation (Lower Cretaceous) in the Yellow River (Huang He) valley represent the first significant fossil footprint discoveries in Gansu Province, China. However, the sites are large, visually spectacular, and well-exposed thanks to labor-intensive hand excavation. The sites have the potential for development as educational and tourist destinations. These sites have become one of the National Geoparks in China.
Dinosaur tracks include at least two theropod morphotypes that range in size from about 5 to >30 cm in length. Wide-gauge sauropod tracks (Brontopodus) range in size from 25 to 90 cm (pes length) and are the best-preserved examples known from China, with clear claw impressions. One trackway suggests an accelerating/running individual. Parallel ornithopod trackways indicate gregarious behavior. An enigmatic trackway may be a manus-only ornithopod trackway.
A pterosaur trackway (cf. Pteraichnus), the first reported from China, consists of 24 consecutive footprints, and is the longest, well-preserved trackway on record. Bird tracks (cf. Aquatilavipes) are also very well preserved.
The tracks occur at multiple stratigraphic levels in fluvio-lacustrine sequences of paleosol mudstones and sandstones with mud cracks and wave ripple marks. A minimum ichnodiversity of eight, the highest reported from the Cretaceous of China, is estimated. The saurischian component (theropods and sauropods) compares well with Inner Mongolia ichnofaunas from the Jing Chuan Formation. However, the co-occurrence of ornithopod and sauropod tracks is rare in Asia and globally, and compares with assemblages from South Korea, a similar Cretaceous paleolatitude (ca. 30°).

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Dr Ian West, author of these webpages

Webpage - written and produced by:


Ian West, M.Sc. Ph.D. F.G.S.

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at his private address, Romsey, Hampshire, kindly supported by Southampton University,and web-hosted by courtesy of iSolutions of Southampton University. The website does not necessarily represent the views of Southampton University. The website is written privately from home in Romsey, unfunded and with no staff other than the author, but generously and freely published by Southampton University. Field trips shown in photographs do not necessarily have any connection with Southampton University and may have been private or have been run by various organisations.