Studies on the Vertebrate Palaeontology of the Oxford Clay (Jurassic) of England

This thesis reports studies on the taxonomy, palaeoecology and diagenesis of vertebrate fossils in the Oxford Clay, with particular emphasis on the taphonomy. Vertebrates are abundant in the Lower Oxford Clay, but they become rare higher in the succession. There is a correlation between abundance and faunal diversity with organic carbon content of the clay. Five types of vertebrate preservation can be recognised based on the completeness of the skeleton and the amount of disarticulation due to sedimentological factors. Diagenesis and compaction drastically affect the preservation of vertebrate remains. In the Lower Oxford Clay compaction may be responsible for up to 75% volume reduction. Pyrite and calcareous concretions commonly occur around Oxford Clay vertebrates where they may protect skeletons from compaction. Late septarian cracking of the concretions may cause severe brecciation of the bone. The vertebrate fauna of the Oxford Clay is diverse and includes ichthyosaurs, plesiosaurs, pliosaurs and crocodiles as well as fish and non-marine reptiles. An allochthonous dinosaur fauna shows affinities with Middle Jurassic faunas in South America, Morocco and China, indicating a cosmopolitan dinosaur fauna world wide during the Jurassic. The fish fauna of the Oxford Clay is one of the richest in the north west European Middle Jurassic. It contains a variety of trophic groups, and an even greater diversity of morphotypes. The new species Coccolepis dawni, Caturus megadontus and Asthenocormus cornishii are recognised. The new genus Fensia is established for the new species F. tuberculata.