A fishy mosasaur: the axial skeleton of Plotosaurus (Reptilia, Squamata) reassessed
Article first published online: 1 MAR 2007
Volume 40, Issue 2, pages 153–160, June 2007
How to Cite
LINDGREN, J., JAGT, J. W.M. and CALDWELL, M. W. (2007), A fishy mosasaur: the axial skeleton of Plotosaurus (Reptilia, Squamata) reassessed. Lethaia, 40: 153–160. doi: 10.1111/j.1502-3931.2007.00009.x
- Issue published online: 8 APR 2007
- Article first published online: 1 MAR 2007
- Received 27th January 2006, revised 27th November 2006.
- Displacement unit;
- propulsive surface;
- tail fin;
- tail stock
The concept of convergence, that is, how unrelated animals independently evolve similar morphological traits, is a fundamental aspect of evolution. Hitherto, the Mesozoic ichthyosaurs were regarded as the sole obligate marine reptiles that achieved a fully streamlined body and a semilunate tail fluke. However, analyses of vertebral centrum morphometrics and process orientation have revealed that a subsequent clade of secondarily aquatic reptiles, the mosasaurs (here exemplified by the advanced, mid-Maastrichtian mosasaurine Plotosaurus), had developed a deep, fusiform body and a probable pursuit-predatory behaviour by the time of their sudden extinction at the Cretaceous–Paleogene boundary. Stringent physical constraints and selection pressures, imposed by the surrounding water, probably were responsible for this spectacular example of large-scale evolutionary convergence.