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Spinosaurid quadrate morphofunctional analysis suggests two spinosaurs in North Africa

Ben Creisler

New in PLoS ONE:

Christophe Hendrickx, Octávio Mateus & Eric Buffetaut (2016)
Morphofunctional Analysis of the Quadrate of Spinosauridae
(Dinosauria: Theropoda) and the Presence of Spinosaurus and a Second
Spinosaurine Taxon in the Cenomanian of North Africa.
PLoS ONE 11(1): e0144695. doi:10.1371/journal.pone.0144695

Six quadrate bones, of which two almost certainly come from the Kem
Kem beds (Cenomanian, Upper Cretaceous) of south-eastern Morocco, are
determined to be from juvenile and adult individuals of Spinosaurinae
based on phylogenetic, geometric morphometric, and phylogenetic
morphometric analyses. Their morphology indicates two morphotypes
evidencing the presence of two spinosaurine taxa ascribed to
Spinosaurus aegyptiacus and? Sigilmassasaurus brevicollis in the
Cenomanian of North Africa, casting doubt on the accuracy of some
recent skeletal reconstructions which may be based on elements from
several distinct species. Morphofunctional analysis of the mandibular
articulation of the quadrate has shown that the jaw mechanics was
peculiar in Spinosauridae. In mature spinosaurids, the posterior parts
of the two mandibular rami displaced laterally when the jaw was
depressed due to a lateromedially oriented intercondylar sulcus of the
quadrate. Such lateral movement of the mandibular ramus was possible
due to a movable mandibular symphysis in spinosaurids, allowing the
pharynx to be widened. Similar jaw mechanics also occur in some
pterosaurs and living pelecanids which are both adapted to capture and
swallow large prey items. Spinosauridae, which were engaged, at least
partially, in a piscivorous lifestyle, were able to consume large fish
and may have occasionally fed on other prey such as pterosaurs and
juvenile dinosaurs.