Université de Liège

Graduate Student, Géologie

Other Affiliations: Royal Belgian Institute of natural Sciences, Palaeontology

Thesis Title: Evolution and extinction of Cretaceous ichthyosaurs

About

-Interests-

Ichthyosaurs, Mesozoic marine reptiles, palaeoecology especially niche partitioning, tooth morphology and wear, Extinction events (mainly JCB and CTB)



-Brief overview and latest news of my ongoing thesis work- (dec. 2010)

    Amongst Mesozoic marine reptiles (MMR), ichthyosaurs were indisputably the most successfully adapted to the marine environment. Ichthyosaurs are a peculiar group within MMR, being the first to appear right after the Permo-Trias event, but also the first major group to disapear, meeting their demise during the Cenomanian-Turonian boundary event, some 28 million years before the K/T boundary event, responsible for the complete extinction of most other MMR groups (mosasaurs, plesiosaurs, and several families of marine turtles and marine crocodiles). If the Cenomanian-Turonian boundary is usually associated with an ecological crisis within the marine realm, the magnitude, tempo, and causes of this crisis are still poorly understood. New findings from France and Russia also indicates that the current hypotheses formulated to explain the demise of ichthyosaurs are now unsatisfactory (see "abstracts": Fischer et al, 2009; Fischer, 2010a, b.).

    Considered as the last survivors of a dying group, all Cretaceous ichthyosaurs have traditionally been incorporated within a single genus, Platypterygius. Nevertheless, diagnostic characters for Platypterygius and its species are in most cases useless, or even inexistent. Furthermore, new taxa from SE France (Fischer et al., 2009; Fischer, in prep.), North America (Maxwell & Caldwell, 2006; Druckenmiller & Maxwell, 2010) and Russia (Fischer et al., in review) exhibit caracters previously considered as autapomorphic for Platypterygius (root with squared cross-section; thighly packed rectangular phalanges, humerus with extremely prominent trochanter dorsalis and deltopectoral crest, etc.).  This indicates the radiation of Ophthalmosauridae was rather "messy" and highly homoplasic (Maxwell, 2010; Fischer et al., in review) and that the genus Platypterygius needs to be thoroughly revised. This revision is being carried on the morphological, "phenetical" and phylogenetical grounds.

    Moreover, recent discoveries clearly indicate that other ichthyosaur genera were present by Early Cretaceous times besides Platypterygius: Caypullisaurus (Fernàndez & Aguirre-Urreta, 2005; Fernàndez, 2007), Brachypterygius and possibly Ophthalmosaurus (McGowan & Motani, 2003); Maiaspondylus (Maxwell & Caldwell, 2006), some russian genera (Ochev & Effimov, 1985; Effimov, 1997; Fischer et al. in review.), Yasykovia (Efimov & Komarov, 2010), and Aegirosaurus (Fischer et al., in press).

  These new discoveries suggest that the diversity of Early Cretaceous ichthyosaurs, especially during the Aptian-Albian, is now far higher than previously supposed, both from taxonomical and ecological points of view. Ichthyosaurs actually colonized new ecological niches during the Cretaceous, including potential apex predators (Fischer, in prep.) or specialized "fish" hunters (Fischer et al., 2009b; Fischer, in review.), and more generalistic niches (Fischer et al., in press). Their extinction during the Cenomanian is thus far more severe than previously supposed and needs a complete reinvestigation (Fischer, 2010a, b; Fischer, in prep.).

Contact Information