presented. Several new proposals are made for the measurement and classification of fossil footprints. Field studies by the author have revealed many new vertebrate footprint discoveries in the British Triassic, including one at Hilbre, Wirral which is one of the most complete footprint assemblages found in recent years. Field case studies are presented for three localities: The Bendricks in S, Wales, Hilbre Island, Wirral, and Hollington, Staffordshire. New discoveries at Hollington confirm that the site has a typical Mid Triassic assemblage of footprints of medium-sized archosaurs (Chirotherium sp.) and small diapsids (Rhynchosauroides sp.). The Hollington footprint assemblage is comparable to better-known assemblages from Storeton and Runcorn in Cheshire dated as Lower Anisian. The sedimentary nature and organisation of the lithofacies suggests a fluvial environment which was initially of low sinuosity but became more sinuous later. A major review of the ichnofamily Chirotheriidae in the British Triassic shows that there are at least three valid ichnospecies of Chirotherium, one of Synaptichnium, and one of Isochirotherium. The presence of a fourth related ichnogenus. Brachychirotherium. is unclear and cannot yet be confirmed in Britain. A comparison of the lithostratigraphy of footprint localities shows that Chirotherium. Synaptichnium and Isochirotherium can only be confirmed in British Middle Triassic rocks of Lower - Middle Anisian age. These results are almost certainly not a true reflection of the stratigraphic distribution of these ichnogenera, but probably highlight the facies dependant nature of footprint preservation. Probable Chirotheriidae footprint forms occur throughout the British Triassic in rocks of Lower Scythian to possibly Upper Norian age. Unfortunately, the quality of Lower and Upper Triassic specimens obtained to date is relatively poor; hence identification of these footprints to ichnogenus level is difficult. A taxonomic review of the morpho-family Rhynchosauriidae in the British Triassic was undertaken. There is evidence to suggest that the "Rhynchosaurus" footprints found by Ward at Grinshill, Shropshire, in 1838, which later gave rise to the establishment of the ichnogenus Rhynchosauroides. should be reassigned to the ichnogenus Rotodactylus Peabody 1948. This study confirms the occurence of Rotodactyl us in the British Triassic. Twenty British Triassic footprint forms that have been previously, or are presently, assigned to the ichnogenus Rhynchosauroides, together with five other related forms have been restudied. Two are considered to be Rotodactylus sp.; one is reassigned to the chirotheroid ichnogenus Synaptichnium sp.; five are considered poorly preserved examples of either Rotodactylus or Rhynchosauroides and have been reassigned to ichnogenus indet; one is considered to be an inorganic sedimentary structure and is referred to ichnotaxa indet; and only six are considered to be forms of Rhynchosauroides. Rhynchosauroides is recorded and confirmed from at least twelve British localities, and Rotodactylus from seven.The lithostratigraphic range of Rotodactylus is ?Middle Scythian - Middle Anisian, Lower - Middle Triassic. The lithostratigraphic range of Rhynchosauroides is ?Middle Scythian -Upper Carnian (possibly Norian), Lower - Upper Triassic. The oldest skeletons of dinosaurs date from the Late Triassic (Carnian) but supposed dinosaur footprints have been reported from Early and Mid Triassic ;rocks dated up to 20 Myr: ~earlier. A restudy of several.museum specimens was undertaken; supposed Lower Triassic dinosaur footprints from Britain are reinterpreted as ripple marks, mud rip-up clasts, and possible limulid prints. The Middle Triassic material is reinterpreted as partial specimens of Chirotherium , presumably produced by rauisuchians and one indeterminate specimen, possibly also of chirotheroid affininites. The oldest dinosaur footprints from Britain come from the marginal Triassic (Non an, Upper Triassic) in South Wales. Elsewhere 10 the world, the oldest dinosaur footprints appear to be Carnian corresponding in age to the oldest skeletal remains
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:245368 |
| Date | January 1997 |
| Creators | King, Michael John |
| Publisher | University of Bristol |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1983/4eb2ea29-cade-4ea6-b58e-ccf3fde2bdd0 |
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