Dan,
While I have no problem with a tail bend in the vertebral column... do we have any evidence that it would actually be visible as a drop in the tail itself?
One of the things I liked about your original broad, blunt version of the tail was that it could support either version on the terminal portion of the vertebral column.
Somehow, they reverted back to the sharply pointed terminus.
Mike
At least you have Lindgren
et al., 2003; here is the abstract:
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.
I've the .pdf version of this article, just PM me.
Plotosaurus seems to have modified neural spines at the very end of its tail. They show a tail fluke similar to that of Triassic ichthyosaurs such as
Californosaurus on
Plotosaurus.
Lindgren J, Jagt JWM & Caldwell MW.
2007. A fishy mosasaur: the axial skeleton of Plotosaurus (Reptilia, Squamata) reassessed.
Lethaia,
40: 153-160.
Valentin
