INTRODUCTION

Liassic Fossils at Lyme Regis and Charmouth.
(collecting is more difficult than might be expected!)

Lyme Regis is, of course, famous for its Liassic fossils. Some introductory information and illustrations of selected species are given below. Good specimens are not as easy to find as in the past. This is partly because of sea defences obscuring some of the section, but particularly because there are numerous collectors in the area, including professional collectors who obtain specimens for shops or sell them directly. The cliffs are searched over very thoroughly. In spite of this it is possible to find some good fossils and the common ones are frequently seen, of course.

For those interested in serious fossil collecting please follow the policies of Jurassic Coast, the UNESCO World Heritage Coast. Note that some land in the area belongs to the National Trust. Charmouth Parish Council controls cliffs between Lyme Regis and Hythe Beach at Burton Bradstock. The fossil collecting codes of conduct for thes area should be consulted.

A good perspective on fossil collecting in the Lyme Regis area has been given, many years ago, by Dr. W. D. Lang, the famous Lias specialist:

"Introduction:
Visitors to Charmouth and Lyme who come with intention of finding fossils are often disappointed at the results of their collecting. Those to whom the fossils appeal chiefly as specimens of form and shape, having heard much of Lyme as a collecting ground, seen in museums fossils from the neighbourhood in numbers and in fine preservation, and read their descriptions in the works of De la Beche, Buckland, Sowerby, and others learn by experience that specimens such as they expect to find are commonest in the cottages of fishermen and in the shops of Lyme. Those, on the other hand, whom the evolutionary history and, consequently, the order of succession of the fossils interests, learn that for one specimen found in place in its bed, twenty are picked up loose on the cliff-slopes and on the beach. It is true that a large amount of time and labour are necessary, whether for obtaining fine specimens or a succession of forms whose exact horizon is known; and really to learn their evolutionary sequence it is essential either to live in the neighbourhood for some time or regularly to revisit the locality for a great number of years. Thus it is that, although hundreds of species are known and described from the Lyme district, our knowledge of their exact horizons, so necessary for unravelling their evolution, is very small. And to help towards this end has been the chief motive of the work resulting in these notes." [Now reade the classic works of (Lang, 1914; 1924 etc)

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Ammonites - Introduction

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Large ammonites occur in the loose blocks on the shore as shown above at Chippel Bay, and are also present at East Cliff and Church Cliffs, Black Ven, Charmouth and localities further east. The specimen in the ledges have been eroded through to some extent.

The organisms once living in these shells were extinct cephalopods, members of the Subclass Ammonoidea of the Mollusca. They were related to the nautilus which has survived the Cretaceous/Tertiary extinction, and also to the octopus (Coleoidea). The animal swam in the sea like a nautilus or a squid and had tentacles; it also had internal chambers in the shell which contained varying gas content so that the animal had hydrostatic control and could vary its depth in the water. Cephalopods are restricted to fully marine water, and thus the presence of ammonite is informative regarding salinity. They were dominantly nekton, although some were benthonic but never sessile.

Shown above is a pavement of large arietitid ammonites at Chippel Bay, Lyme Regis. They are in the Top Tape, Lang's bed 29, 80 cm above the Mongrel and in the bucklandi zone (see the graphic log in the Lyme - West Webpage.
Right: A similar pavement in the same general part of the Blue Lias at Church Cliffs to the east of Lyme Regis town.

The abundance of ammonites in such Liassic limestone may be because they accumulated on the sea-floor when sedimentation was slow. The ammonite are not suitably preserved for proper identification but they are probably Arietites (Coroniceras).

Ammonites - Arietitids - Paracoroniceras lyra

A fine ammonite specimen has been carefully prepared, and the finished ammonite is shown in this photographs. This been identified by Murray Edmunds as Paracoroniceras lyra Hyatt. It is from the lyra Subzone at the base of the Semicostatum Biozone, high in the Blue Lias of Chippel Bay. The specimen was found and excavated by Martin Foster, Mark Hawkes and Ian Troth in the summer of 2001. Dr. Ian Troth, shown with the specimen, is a petroleum and gas exploration geologist, a former student of Southampton University, and is a keen fossil collector.

The original specimen was a grey block of limestone on the shore with just part of an ammonite showing. Preparation by Mark Hawkes from Stone Treasures, has revealed not only the excellent shell of the ammonite but also a nautiloid that was in the same block. Ian Troth considers that the nautiloid was originally beneath and that the ammonite shell fell onto it. Early cementation of the argillaceous limestone bed in the Blue Lias prevented major compaction from taking place. Only some minor breakage of the nautiloid body chamber has taken place from the ammonite pressing down on it. Arnioceras shells are present on the other side of the block and it has almost certainly come from the semicostatum zone, perhaps from Grey Ledge.

It should be stressed that this is a rare specimen. Ammonites of this species are not as well preserved as the above specimen from this locality in general. This is because the umbilicus, the first few whorls, is often missing. Collection is difficult because of the weight Although there are specimens loose on the beach, the majority are waterworn and incomplete. They are perhaps best left for others to see.

Notice the strong, well-spaced ribs which are near rectiradiate (i.e. radial) except for the forward deflection at the venter (the outside). A tricarinate keel (three ridges on the venter) is present.

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Ammonites - Arietitids - Arietites bucklandi
("Coroniceras bucklandi")

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(See also: Huge Arietites Ammonite - Schoppenstedt, Braunsweig, Germany. "This massive Arietites bucklandi ammonite was recently discovered by accident during utility construction near a small town in north central Germany. We were very fortunate to secure such a rare example in the matrix to where we can conduct the delicate preparation needed to best care for its fragile features. Note the intricate inner chamber structures still preserved and intact as seen in the second to last image")

Arietites is a member of the Superfamily Psilocerataceae. Thus it is related to Psiloceras the ammonite which occurs in the lowest part of the Lias. The Psilocerataceae are a group of diversely ornamented generally evolute to subevolute shells arising from smooth-ribbed and unsculptured ancesters and progressively developing ribs, vertical chevrons or keels, often angular, or tricarinate venters. They are usually with strong lateral ribs and some are evolute oxycones. They may have developed from Triassic Ceratitina or Phlloceratida (House, 1985).

Arietites, as a genus, is characterised by often very large evolute shells with subquadrate whorl section with tricarinate and bisulcate venter and strong, near-rectiradiate ribbing on the flanks. It is only from the Lower Jurassic, Lower Sinemurian, from Europe to S.E. Asia and in the Americas (House, 1985).

Above is a small pyritised ammonite, probably Arietites. Pyrite has replaced the original aragonite shell in this specimen.

Ammonites and the Reverend William Buckland

A famous early geologist who studied such ammonites was the Reverend William Buckland (1784-1856), Canon of Christ Church and Reader in Geology and Mineralogy at the University of Oxford, after whom the Arietites bucklandi zone, to which these strata belong, is named. He was President of the Geological Society of London from 1824-1826 and from 1839-1841. He was much involved with the fossils of Lyme Regis and some of his figures are reproduced here. William Buckland was 59 in 1843 when this painting was made. (Source - Woodward, 1907)

Buckland was an amiable and eccentric Oxford don with a sense of humour. Woodward (1907) noted that " Buckland, always an enthusiastic collector, once found a large form of Ammonites Bucklandi (now Coroniceras bucklandi or Arietites bucklandi ) without the inner whorls. An example of such an ammonite is shown above. He thrust his head through the stony ring and rode home, dubbed by his friends the " Ammon Knight ".

The Reverend William Buckland habitually carried a large blue bag for his fossils, and has told that the greatest honour which the bag ever had was when Lord Grenville insisted on carrying it; and the greatest disgrace it ever had was when he called on Sir Humphrey Davy three or four times one day and always found him out. At last Sir Humphrey asked his servant, " Has Dr Buckland not called to-day?" " No, sir, there has been nobody here to-day but a man with a bag, who has been here there or four times, and I always told him you were out. "

More Ammonites

Shown above are ammonite remains in one of the hard argillaceous limestones of the Blue Lias. An eroded specimen showing sediment fill of the body chamber. Fossil remains like this are very common in the stone bands and you will see many specimens as you walk over the ledges on the beach. Ammonites in the stone bands are uncompacted whereas those in the associated shales are usually compacted. Look out too for the large and wider nauliloid shells in the stone bands.

Asteroceras obtusum (the " Obtuse Star Ammonite ") as figured by the Reverend William Buckland in 1837. This and the " True Star Ammonite " - Asteroceras stellare come from the Black Ven Marls (stellare nodules etc) , higher in the cliff but may be found on the beaches as a result of landslips. Ammonites rather like these can be purchased in the fossil shops of Lyme Regis. The mother-of-pearl aragonite has been replaced by calcite in these ammonite fossils. Note that Buckland figured this specimen the right way up. The octopus-like animal lived underneath as does the modern pearly nautilus.

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Ammonite found by Ian Troth

A specimen of Harpoceras falciferum found in the Lias at Whitby in Yorkshire by Ian Troth and cleaned by Stone Treasures. Other Liassic ammonites can be obtained from Stone Treasures of Edwinstowe, Nottinghamshire or Stone Treasures Website .

Yet More Ammonites

Amaltheus margaritatus, Middle Lias, Dorset. Specimen found by Ian Troth. The ammonite was prepared by Mark Hawkes from Stone Treasures.

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Bivalves

Plagiostoma gigantea (the oblique-mouth giant shell) is a large black shell that is common in the ledges and becomes larger higher in the succession. It quite easy to find although most specimens which you see will be worn or damaged in some way.

Gryphaea arcuata Lamarck, a Jurassic oyster which is colloquially known as the "Devil's Toe-nail" (and once named "Gryphaea incurva"). This asymmetrical oyster-like bivalve lived in the mud on the early Jurassic sea-floor. A set of Gryphaea shells worn through can be seen in some of the ledges, as shown above. Many that are visible in section, but good complete specimens are difficult to find here. For more information on Gryphaea arcuata see the book: Gould, S.J. 1980. The Evolution of Gryphaea (available online).

(Historical note: In the past Gryphaeas were worn in the Scottish Hebrides as amulets and considered to have curative value for pains in the joints. In Gloucestershire powdered Gryphaea arcuata of the Lower Lias was mixed with whey and used as medicine for cattle (Woodward, 1911).)

In an argillaceous limestone of the Blue Lias at the foot of Church Cliffs examples can easily be found of the Devil's Toenail. Gryphaea arcuata Lamarck, once more commonly know as Gryphaea incurva, are seen at the top of a stone band and have been cut through by some sea erosion of the ledge. This small but robust mollusc, Gryphaea was an epifaunal (i.e. non-burrowing), suspension feeder (feeding on minute suspended animal life etc) that in adult life lived reclining on the sediment surface. Notice how the larger valve is downwards resting on what was once soft mud. The shell is now of calcite and probably always was, rather than aragonite. It is thicker in the umbo region. Note that the shells are in place here and would be classified as a life-assemblage. The sea-floor was presumably below storm wave-base. The presence of a benthic fauna here shows that at the time of deposition of this bed the sea-floor was not anoxic (it is something that the association with bituminous shale might have suggested). The genus Gryphaea had a range from late Triassic to late Jurassic, but this species was typical of the Lower Lias and is very widespread. The book, incidently, is "British Mesozoic Fossils" from the Natural History Museum, London and useful for identifying the common Liassic fossils. Unfortunately it is probably out-of-print now.

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Brachiopods

Calcirhynchia calcarea is common in the Blue Lias. These are small rhynchonellid brachiopods, usually with sparry calcite interiors in the limestone bands at Lyme Regis.

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Crinoids

Above is an old illustration from (Buckland, 1837) of Pentacrinites fossilis, the pentagonal sea-lily of the Lias of Lyme Regis (but an animal - an echinoderm), and beneath it a modern living relative. Complete fossil specimens are rare but the isolated columnals or parts of the stem are easily found in the appropriate beds (marl - 22d - a third of a metre beneath the Mongrel and in bed 32g).

(The main Pentacrinite Bed (of Woodward and Ussher, 1906) is higher in the Lias and not seen on this particular field trip. It occurs in the Black Ven Marls east of Charmouth, on which useful information is provided in a Web Site by Caselton. It is shown as bed 84b in a diagram provided by that author.)

Pentacrinites columnals (parts of the stem) have been known as "St Cuthbert's Beads " and those from the Oxford Clay (higher in the Jurassic) have apparently been worn as ornaments by ancient Britons (Damon, 1884).

The fossil crinoid shown above " represents a single specimen of Briarean Pentacrinite, which stands in high relief upon the surface of a slab of Lias from Lyme Regis, almost entirely made up of a mass of other individuals of the same species. The arms and fingers are considerable expanded towards the position they would assume in searching for food. " (Buckland, 1837).

The name " Briarian Pentacinite " had been given to this species by Miller because of comparison with the Greek mythical monster Briareus which had a hundred hands (but, however, Pentacrinus briareus was not the first name given and thus was subsequently declared invalid).

The modern relative on the right is brightly coloured and many are orange or yellow. This particular example is not an entirely satisfactory comparison because it differs in having no stem and lives on coral reefs. It does, however, similarly use the arms to feed on suspended matter in the water (in this case at night). A closer living relative of the Liassic Pentacrinus has been found in deep seas in the West Indies (as noted by Buckland, 1837). Thus similar creatures live today but not, perhaps, in the same ecological niche.

(" The Briarian Pentacrinite was a locomotive animal having the power of attaching itself temporarily either to extraneous floating bodies, or to rocks at the bottom of the sea, either by its side arms, or by a moveable articulated small root. " (Buckland, 1837).

Evidence that the crinoids were attached to floating wood comes from some comments from the famous collector Mary Anning to the Reverent William Buckland (1837). " Throughout nearly its whole extent, Miss Anning has constantly observed in this Lignite the following curious appearances: The lower surface only is covered by a stratum, entirely composed of Pentacrinites, and varying from one to three inches in thickness; they lie nearly in a horizontal position, with the foot stalks uppermost, next to the lignite. The greater number of these Pentacrinites are preserved in such high perfection, that they must have been buried in the clay that now invests them before decomposition of their bodies had taken place. It is not uncommon to find large slabs several feet long, whose lower surface only presents the arms and fingers of these fossil animals, expanded like plants in a Hortus Siccus; whilst the upper surface exhibits only a congeries of stems in contact with under surface of the lignite. The greater number of these stems are usually parallel to one another, as if drifted in the same direction by the current in which they last floated.

The mode in which these animal remains are thus collected immediately beneath the Lignite, and never on its upper surface, seems to shew that the creatures had attached themselves, in large groups, (like modern barnacles), to the masses of floating wood, which together with them, were suddenly buried in the mud, whose accumulation gave origin to the marl, wherein this curious compound stratum of animal and vegetable remains is imbedded. Fragments of petrified wood occur also in the Lias, having large groups of Mytili, in the position that is usually assumed by recent mytili, attached to floating wood. "

The drifting wood is itself a matter of interest in showing the proximity of land. Cornubia was not far away (Cope, Ingham and Rawson, 1992).

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Nautiloids

A good specimen of a nautilus, Cenoceras striatum found at Lyme Regis by Ian Troth, a student at Southampton University. The specimen was prepared by Mark Hawkes from Stone Treasures. Worn specimens of nautiloids can quite commonly be found on the foreshore west of Lyme Regis but are not well-preserved and best left for others to see.

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Fish

Most of the fossil fish from the Blue Lias come from the Fish Bed and the Fish Bed Shales near the top of the Blue Lias, and just below the Saurian Bed.

The Liassic bony fish were of ganoid type belong to the Superorder Holostei (Romer, 1945). These holostian fish were very abundant in the Mesozoic but are only represented at the present time by two American freshwater fish - the garpike, Lepidosteus, and Amia, the so-called dogfish or bowfin. The Liassic Dapedius was a deep-bodied holostean fish belonging to the Semionotidae. The short mouth was armed with peglike or rounded teeth, indicating that some hard type of invertebrate material formed the food supply. The scales are thick and shiny rhomboidal structures, with a heavy layer of ganoine, a type of enamel, on bone. Pholidophorus, also occurring in the Lias, was a relatively advanced Jurassic holostean fish. For more information see Romer (1945).

For information on Acrodus anningiae Agassiz see Day (1864). For some recent finds of fossil fish from the Dorset Lias, including Dapedius from the Gumption Shales see: Key Scientific Important Fossil Recording Scheme, Vertebrate Fossils - Fish .

The following are records of Liassic Fish from Lyme Regis in the Natural History Museum, London, recorded by Woodward, A.S. (1895), in Part 3 of his work. Although containing almost all in this volume, it is not claimed to be necessarily a complete list. Reference should be made to all the original four volumes of this publication on Fossil Fishes in the British Museum (Natural History), now known as the Natural History Museum, South Kensington, London. Large numbers are not likely to be given in the other volumes. The names have not been updated but are as given in 1895, and specimens quoted as from Lyme Regis have been counted. Liassic fish not from Lyme Regis have been ignored.

Lower Lias Fish belonging to the Actinopterygian Teleostomi: recorded from the Lyme Regis neighbourhood and preserved in the Natural History Museum, London.

Belonorhynchus acutus, (Agassiz). - 13 specimens.
Belonorhynchus brevirostris, Woodward. - 6 specimens.
Chondrosteus acipenseroides, Egerton. - 26 specimens.
Dapedius politus, Leach. - 44 specimens.
Dapedius radiatus, (Agassiz). 6 specimens.
Dapedius colei, Agassiz. 15 specimens.
Dapedius punctatus, Agassiz. 19 specimens (one in a septarian nodule).
Dapedius granulatus, Agassiz. 23 specimens.
Dapedius magnevillei, Agassiz. 16 specimens.
Eugnathus orthostomus, Agassiz. 16 specimens.
Eugnathus philpotae, Agassiz. 23 specimens.
Eugnathus minor, Agassiz. 17 specimens.
Eugnathus serratus, (Davis). 1 specimen.
Eugnathus altus, Woodward. 1 specimen.
Heterolepidotus latus, Egerton. 16 specimens.
Ptycholepis gracilis, Davis. 3 specimens.
Ptycholepis curta, Egerton. 6 specimens.
Ptycholepis monilifer, Woodward. 1 specimen.
Osteorachis macrocephalus, Woodward. 7 specimens.
Osteorachis granulatus, Woodward. 1 specimen.
Caturus heterus, (Agassiz). 15 specimens.
Caturus latipennis, (Egerton). 2 specimens.
Caturus agassizi, (Egerton). 2 specimens.
Caturus (Conodus) chirotes, (Agassiz). 3 specimens.
Pholidophorus bechei, Agassiz. 37 specimens.
Pholidophorus pachysomus, Egerton. 11 specimens.
Pholidophorus caudalis, Woodward. 26 specimens.
Pholidophorus crenulatus, Egerton. 11 specimens.
Pholidophorus limbatus, Agassiz. 10 specimens.

A further brief reference to fish was made by Horace Woodward (1889) in an account of a field excursion to Lyme Regis:

"Remains of Fishes are also abundant, although their horizons are not so well known. They include species of Acrodus ("fossil leeches"), Hybodus, Eugnathus, Lepidotus, Aechmodus, and Pholidophorus, many of which occur in the zone of Ammonites obtusus."

Later, Owen (1861-1881) explained that
" the continued attention paid by James Harrison, Esq., to the organic remains discovered during quarrying operations on the face of the cliff of Lower Lias at Charmouth, Dorsetshire, with liberal encouragement to the workmen, has procured for the original discoverer of the first indication of the Scelidosaur the materials for the present account of an almost complete skeleton of that extinct reptile. Following in the track opened out by the discovery of the skull described in the preceding Monograph, about twelve successive blocks of Lias were secured, with more or less evident indications of included bones, all of which, together with the skull, have been purchased for the British Museum. Subsequent complete exposure of the included organic remains has brought to light the entire vertebral column of the trunk and tail, to very near the termination of the latter..."

The horizon and locality of the original find by Harrison is just given as the upper part of the Lower Lias near Charmouth. He found the nearly complete skeleton possessing the imperfect cranium (specimen R. 111 of the Natural History Museum) in the Lias near Charmouth. The Natural History Museum purchased the bones in 1865. The length of the specimen is 3.4m.

It is of interest that sometime before 1959, as reported in Delair (1959), additional bones of a supposed immature individual were found in a Flatstone Nodule (Black Ven Marls - obtusum Zone) by Black Ven, near Charmouth by J.F. Jackson, Esq. These remains are also in the Natural History Museum. Thulborn (1977), however, considered these to be unrelated and to be the remains of a lightly built ornithopod adapted for cursorial locomotion. He was definate in stating that it is not a close relative of Scelidosaurus harrisonii.

Very good information on Scelidosaurus harrisonii is given in the webpage:
Scelidosaurus - Scelidosaurus harrisonii. This webpage is a post by "dinomike" on Dec. 3rd, 2010.

The classification of Scelidosaurus harrisonii is summarised as:

Order: Ornithischia
Suborder: Thyreophora
Infraorder: Ankylosauria
Family: Scelidosauridae
Genus: Scelidosaurus
Species: Sceldidosaurus harrisonii

The good skeletal remains come the Charmouth and Lyme Regis area. In 1989, some fossil scutes identified as belonging to Scelidosaurus, were found in the Kayenta Formation (Glen Canyon Group) of northern Arizona. The assignment to Scelidosaurus has been disputed, though.

Description (After "dinomike" - see above):

A full-grown Scelidosaurus was rather small, compared to most other dinosaurs. Some vertebrate palaeontologists have estimated a length of 4 metres (13 ft) Scelidosaurus was quadrupedal, with the hindlimbs considerably longer than the forelimbs. It may have reared up on its hind legs to browse on foliage from trees, but its forefeet were as large as its hind feet, indicating a mostly quadrupedal posture. Scelidosaurus had four toes, with the innermost digit being the smallest. It has bony scutes in the skin. The dinosaur had very small leaf-shaped cheek teeth suitable for cropping vegetation. For information on the skull see Norman and Charig (1996)

Of particular interest is the report of the preservation of soft tissue in a specimen of Scelidosaurus byMartill et al. (2000). These fossil remains consist of eight caudal vertebrae in a cut slab of carbonate mudstone, which was judged to date from the late Hettangian to Sinemurian stages. An envelope of preserved soft tissue was visible around the vertebrae, and show the presence of an epidermal layer over the scutes. The authors concluded that the osteoderms of all basal armoured dinosaurs were covered in a tough, probably keratinous layer of skin.

The specimen came from a collection of Professor John Challinor (1894-1990) and was used as a teaching aid at Portsmouth University. It has no label and no provencance data. The matrix is typical of that of nodules of the English Lias. Soft tissue preserved as kerogen is comparable to other vertebrate material from the Sinemurian of Charmouth. Palynological data suggests an Hettangian - Sinemurian age, but an exact horizon has not been fixed.

In the year 2000, the professional fossil collector David Sole discovered the partial remains of a Scelidosaurus, after a cliff fall at Black Ven, near Charmouth. This "Horned Scelidosaur" is extremely well-preserved in three-dimensional form. It has body armour and even evidence of its last meal. The 195 million year old dinosaur remains were further retrieved piece by piece over five years by David Sole.

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Vertebrates, - Ichthyosaurs, Plesiosaurs, Pterosaurs etc.

(See also Ichthyosaur section in the Kimmeridge Fossils Webpage.)

Lyme Regis has long been famous for its " sea-dragons " - the marine reptiles, the ichthyosaurs and the plesiosaurs found by Mary Anning and others. Ichthyosaurs were major sea-reptiles and predators for about 100 million years. After their extinction their ecological niche has been taken over recently by dolphins at the present time. Dolphins are, in effect, modern imitators of ichthyosaurs, and a reconstruction of their ecological (but, of course, not ancestral) predecessors is also included here. The plesiosaurs were long-necked and in their appearance were very unlike creatures living today. Details of both ichthyosaurs and plesiosaurs are discussed below.

For the stratigraphical locations of the main horizon of ichthyosaur and plesiosaur discoveries at Lyme Regis see the Saurian Shales section in the Lyme Regis to Charmouth webpage. See also the Blue Lias - Graphic Log , which has records of the horizons of fossil including these saurians. Note that they are not, by any means confined to the Saurian Shales. Bear in mind that the most notable horizons will have been searched over regularly by professional collectors (some of whom even search underwater by diving). Perhaps a chance discovery elsewhere may perhaps be more likely. When the large skeletons were found in the 19th Century the cliffs were being quarried for cement, facilitating discovery and extraction. Some too were found close to the centre of the town where the cliffs are now obscured by an esplanade and sea-defences.

Thus finding large specimens would require considerable luck. Individual bones, such as these brown, biconcave vertebrae of ichthyosaur can sometimes be found, however. These students are displaying a water-worn example. It may be worth searching for such fossils amongst the patches of pebbles on the ledges like those shown here. If an ichthyosaur vertebra is found, the illustration on the right, based on the 19th Century work of Sir Richard Owen, will enable the position of the vertebra within the animal to be established. It may also be of use for dealing with vertebral centra in museum collections. Plesiosaur vertebra have attached neural spines and look quite different.

This is part of a plesiosaur limb bone and a saurian coprolite (fossil faeces) found by amateur collectors, Paddy Howe and David Sutherland, on the same day as the student field trip took place. The fossils were found in Chippel Bay near the site of a recent cliff fall. A further search did not reveal any more of the plesiosaur, as yet.

Coprolites were once something of a mystery and known as "bezoar stones". They were first recognised as fossil faeces by William Buckland , referred to above.

Ichthyosaurs - Introduction

Bones of marine reptiles of dolphin-like appearance, the ichthyosaurs ("fish lizard"), occur in the marine clay formations of Dorset. These are particularly the Liassic clays, the Oxford Clay and the Kimmeridge Clay Formations. Dorset is historically important because the very first know ichthyosaur was found at Lyme Regis in the Lias by Mary Anning when she was only 12 years old.

The Ichthyosaurs belong to the Order Ichthyopterygia. The Dorset ichthyosaurs were discussed by Delair (1960) in the third part a very useful review of Dorset fossil reptiles. Some notes here are summarised from Justin Delair's account but reference should be made to the original paper for more detailed information.

The Ichthyopterygia are a great Order of reptiles that returned to the sea and became highly adapted to it. They became aquatic during early Mesozoic times and ranged from the Trias to the end of the Cretaceous Period. Their ancestors are not known for certain but they seem to have descended from small Carboniferous reptiles which even at that time were undergoing anatomical changes necessary for an aquatic life. By the time of appearance of the first known genera it is clear that the ichthyosaurs had already had a long history. They were so adapted to the marine environment that they were unable to return to land to lay their eggs and, thus, brought forth their young alive. Fossil skeletons have shown the young ichthyosaurs emerging from the body of the mother.

Delair (1960) has provided a brief description of ichthyosaur characteristics and a simplified version of this is given below:

Ichthyosaurs - Description:

These were large and quite numerous reptiles which had returned to the sea. They had a stream-lined, dolphin-like body without reptilean-type scales. They had four powerful paddle-shaped limbs (the attached photograph is of broad-finned, latipinnate ichthyosaurs of the genus Eurypterygius, - Eurypterygius intermedius and Eurypterygius communis, both species occurring in the Lower Lias of Lyme Regis). Below the strong limb bones of the humerus (upper arm) and femur (thigh bone) the paddle bones are not organised into the usual rows of finger or toe bones but arranged as a flat oar blade. There are many small subcircular or hexagonal bones, with probably not much movement between them. The skull was generally large and, unlike that of most reptles, was joined to the trunk directly and without a neck (note that old reconstructions usually showed a neck but modern ones do not). There was a powerful usually elongated snout armed with numerous powerful teeth. In the skull the nasal openings for the nostrils were placed far back and not at the end of the snout. The round cavities in the skull for the eyes, the orbits, were very large. It is interesting that the eyes were protected by a special circles of hardened (sclerotic) plates, presumably for use in deep diving. The ear-bone, the stapes, was unusually large, probably in connection with diving.

The disk-like vertebrae were very numerous, and separate examples are often found as fossils on the cliffs and beaches where there is Jurassic clay. They are short disks, hollow on both sides (amphicoelous). They are normally separate from the neural arch and spine (spines of the backbone). These round disks of several centimetres diameter are quite distinctive from plesiosaur vertebrae which have neural arches and spines attached, as do those of most dinosaurs. On the cicumferances of vertebrae you can usually see the low projections where neural arches attach and ribs articulate.

A number of perfectly preserved specimens show the body outline of these reptiles. There was a large dorsal fine, but it did not have a bony support and, therefore, was at one time not known to have existed and so it is not shown in the old reconstructions. There was a large asymmetrical tail-fin, in the vertical plane, which was stiffened by a downward bend of the vertebral column (a reversed heterocercal-type fin stiffened by the posterior caudal vertebrae). Swimming seems to have been by fish-like undulations of the body and tail, with the paddle-shaped limbs being used for steering.

The following are illustrations of ichthyosaurs from Rev. William Buckland's (1837), book - Geology and Mineralogy considered with reference to Natural Theology. With them are his comments:

"Nearly at the head of the suprising discoveries, which have been made relating to the family of Saurian, we may rank the remains of many extraordinary species, which inhabited the sea; and which present almost incredible combinations of form and structure; adapting them for modes of life, that do not occur among living reptiles. These remains are most abundant throughout the lias and oolite formations of the secondary series. -----.

Some of the most remarkable of these reptiles have been arranged under the genus Ichthyosaurus (or Fish Lizard), in consequence of the partial resemblance of their vertebrae to those of fishes. ---- . In the same individual, the snout of a Porpoise is combined with the teeth of a Crocodile, the head of a Lizard with the vertebrae of a Fish, and the sternum of an Ornithorhynchus (Platypus) with the paddles of a Whale. The general outline of an Ichthyosaurus must have most nearly resembled the modern Porpoise, and Grampus. ---. Some of the largest of these reptiles must have exceeded thirty feet in length. "

A old comment on the habitat of the plesiosaur was given as follows (H.A. Nicholson, quoted by Webster Smith, 1931):
" That it was aquatic is evident from the form of its paddles; that it was marine is almost equally so, from the remains with which it is universally associated; that it may have occasionally visited the shore, the resemblance of its extremities to those of the turtles may lead us to conjecture; its movements must have been very awkward on land, and its long neck must have impeded its progress through the water, presenting a striking contrast to the organisation which so admirably fits the Ichthyosaurus to cut through the waves."
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Footnote: Plesiosaur History. It has been mentioned to me by Ian Troth that this plesiosaur is in fact also the one illustrated as an etching made in 1863 and reproduced in Osborne (1999, p. 256). The magnificent specimen is Rhomaleosaurus cromptoni, and is the largest fossil plesiosaur found on the Yorkshire coast. It was found on the 27th July, 1848 in the Kettleness alum quarry owned by the Marquis of Normanby. It is 7.11m long (23 feet, 4 inches) and intact apart from one limb and was originally displayed at Mulgrave Castle. The Marquis presented it to Sir Philip Crampton for display in Dublin. It was later in the National Museum of Ireland, but in 1961 a display hall was destroyed to make way for a restaurant and office block. This great plesiosaur fossil was broken up and put in crates in storage where it remains. Casts, however, are in the Natural History Museum in London, the Bath Literary and Scientific Institution and Cornell University in New York.
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"At first view of the framework of the huge head of our Liassic dragon one is struck with the economy of bony material and purposive skell with which it has been applied or disposed, so as to give strength where resisting power was most required. The lodgement of the poorly developed brain enlists a miserably small proportion of the skull: the cranium proper, or brain case, is relegated to an out-of-the-way corner, so to speak, and there it is almost concealed by the projections for joints or muscular attachments. The orbits accord with the large eyes given to this volant and swift-moving reptile....
The main purpose of the head is for prehension of prey. The jaws are produced far forward to form a wide-gaping mouth, and are formidably armed. We may conceive, therefore, that the dragon may have occasionally siezed an animal of such size as to require considerable force of jaw for overcoming its struggles."

Fossil Plants

Two examples of Cycadeoid stems (cycad-like plants) have been recorded from the Lias of Lyme Regis, under the names Cycadeoidea (Yatesia) gracilis and Cycadeoidea pygmaea ( Carruthers, 1870; Seward, 1904). Other cycad remains under the names of , Cycadites, and Otozamites (Otopteris) and the ferns Thinfeldia and Ctenopteris , have been recorded from the Lower Lias of Lyme Regis, Axminster and Membury (Woodward and Ussher, 1911). Pagiophyllum is the foliage of a member of the Araucariaceae. I am grateful to Brian Ottway for drawing my attention to this. If the wood, referred to below is Araucarian it may be compatible with this.

Logs of lignite show that other conifers of the usual tall type (either related to Cypress or to Araucaria) were present in addition to the Cycadophytes in the warm, damp forests at the western margin of this sea, i.e. on Cornubia and Wales. This was before the evolution of the Angiosperms so there were no flowering plants and no grass. Ferns and horsetails would have constitued the low vegetation for browsing dinosaurs.

ACKNOWLEDGEMENTS

I am very grateful to Ian Troth for permission to use photographs of his ammonite specimens. The photographic work of Barry Marsh with regard to fossil specimens is much appreciated. I am grateful for the help of many people on geological field trips with me to the Lyme Regis cliffs. I thank Brian Ottway for information on Araucarian foliage.

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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.

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