Concavispina biseridens (Zhao et al. 2013; Early Late Triassic) is a new thalattosaur that nests with the two Xinpusaurus specimens, but at the base of their clade. Rather than having a sharp-pointed rostrum, Concavispina had a broad, nearly spoon-bill premaxilla. The low blunt maxillary teeth appeared in two rows on each side, an inner and right next to it, an outer. The rostrum and mandible both tilted up. One can imagine this genus was a bottom-feeder, crushing small prey items with that bill and teeth, convergent, perhaps, with the living platypus (Ornithorhynchus anatinus).
Atypical for thalattosaurs, many of the vertebral spines were embayed dorsally, producing two spikes per spine fore and aft. This concave dorsal spine trait inspired the generic name. The twin teeth inspired the specific name. By convergence, there is an almost pre-snake-like morphology here, with such small limbs and so many ribs. Curious that so many sacral transverse processes were present on that odd-shaped ilium. I count five.
The complete reptile family tree is here. |
