Aspects of the microvertebrate fauna of the Early Cretaceous (Barremian) Wessex Formation of the Isle of Wight, southern England

  • Steve Sweetman

    Student thesis: Doctoral Thesis


    Until this study, the microvertebrate fauna of the Early Cretaceous (Barremian) Wessex Formation of the Isle of Wight, southern England,was virtually unknown. A comprehensive survey of potentially productive horizons was undertaken using bulk screening techniques and this yielded an unexpectedly diverse microvertebrate fauna together with fragmentary but significant remains of hitherto unknown elements of the associated macro-fauna. At least forty one previously unrecorded tetrapod taxa have been recovered. Many taxa are generically distinct from those occurring in other coeval European deposits, but in general aspect the faunas are similar. Palaeoenvironmental differences appear to have affected the balance of taxa present but the faunas are dominated by an essentially relictual assemblage of mammals, small theropod and ornithischian dinosaurs, abundant crocodilians, rare pterosaurs and turtles, scincomorph and anguimorph lizards, frogs of discoglossid grade, salamanders and albanerpetontids. The mammal fauna is comprehensively described and detailed accounts of thelepidosaur and archosaur faunas are provided. Space and time constraints do not permit description of the lissamphibian fauna but a summary of this is provided. For the same reason, the fish fauna is described in outline only but the significant occurrence of a neoselachianshark is reported in detail. The taxon concerned represents the earliest record of a neoselachian from a freshwater environment.
    In view of the scarcity of freshwater/terrestrial deposits of Barremian age elsewhere in the world, the Wessex Formation micro-fauna is of considerable importance and complements the already known macro-herpetofauna. This is without parallel elsewhere in Europe and provides a valuable insight into dinosaur faunas and their evolution between the Late Jurassic and mid Cretaceous. Many elements of the Wessex Formation micro-fauna are also encountered in the Early Cretaceous of central and eastern Asia, northern Gondwana and North America.Despite evidence for the existence of marine barriers separating these areas, it is becoming increasingly apparent that faunal interchange between them occurred, albeit perhaps sporadically, during the Late Jurassic and Early Cretaceous. The Wessex Formation microbiota lends further support to this concept and its palaeobiogeographical significance is discussed.Techniques employed in the recovery of the microvertebrate fauna have also resulted in the recovery of previously unrecorded invertebrates and plants. Some of this material may, in due course, allow better dating of the Wessex Formation succession, permit correlation between the south-west and south east-coastal sections on the Isle of Wight and a better understanding of palaeoenvironmental conditions during Wessex Formation times. A brief outline is provided. In view of their palaeontological significance, the plant debris beds of the Wessex Formation are described and conclusions drawn with regard to their genesis.

    Date of AwardApr 2007
    Original languageEnglish
    SupervisorDavid Martill (Supervisor)

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