Taxonomy, phylogeny, palaeobiology, and taphonomy of the Pachypleurosauria (Reptilia: Sauropterygia) from the Lower Muschelkalk of Winterswijk, NL
Final Report Abstract
Data resulting from this project has concretely contributed to the knowledge of alpha taxonomy and diversity of Triassic Eosauropterygia. In addition to the detailed description of the skull and postcranial morphology of the pachypleurosaur, A. heterodontus a new species of Nothosaurus was described (N. winkelhorsti) and its phylogenetic relationships were tested. Additionally, for the first time a postcranial skeleton of a basal Pistosauroidea, most likely Cymatosaurus, was identified with the help of bone histology. Furthermore, its morphology was described, and its phylogenetic relationships were tested. A revised and extended phylogenetic analysis of Triassic Sauropterygia confirmed the monophyly of Pachypleurosauria and this lead to new and interesting questions concerning phylogenetic relationships within the Sauropterygia. The bone histological data not only resolved major taxonomical questions but also showed that some of these marine reptiles had increased growth rates and atypical bone tissue types, at least for reptiles; the data also showed a variety of growth patterns, implying different life histories. Major questions now to investigate are whether the bone tissue type in Sauropterygia was inherited from a terrestrial ancestor or if it represents a new adaptation of some members within the marine environment. A terrestrial ancestor would point to at least two different ancestors and possibly implicate archosaurs as ancestors as well. The advanced bone tissue type which implies increased metabolism for the pistosaur line, is possibly the explanation for why the pistosaurs are the only group of Sauropterygia that survived at the end of the Triassic and the key to why the plesiosaurs had been that successful until to the end of the Cretaceous. The yet unpublished results on taphonomy are most interesting, especially if the low 18 OPo4 value for the Wintersijk fossils can be verified.
Publications
- (2006): Studentische Lehrgrabung im Winterswijker Muschelkalk. Der Präparator 52: 90-96
Dülfer, O. & Klein, N.
- (2009). Nothosaurus winkelhorsti n. sp. from the Lower Muschelkalk of the western Germanic Basin (Winterswijk, The Netherlands). Acta Palaeontologica Polonica 54(4): 589-598
Klein, N. & Albers, P.
- (2009). Skull morphology of Anarosaurus heterodontus (Reptilia: Sauropterygia: Pachypleurosauria) from the Lower Muschelkalk of the Germanic Basin (Winterswijk, The Netherlands). Journal of Vertebrate Paleontology 29(3): 665-676
Klein, N.
- (2010). Long Bone Histology of Sauropterygia from the Lower Muschelkalk of the Germanic Basin Provides Unexpected Implications for Phylogeny. PLoS ONE 5(7): e11613
Klein, N.
(See online at https://doi.org/10.1371/journal.pone.0011613)
