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Makhaira, new pliosaur from Early Cretaceous of Russia (free pdf)
A new paper in open access:
Valentin Fischer, Maxim S. Arkhangelsky, Ilya M. Stenshin, Gleb N.
Uspensky, Nikolay G. Zverkov & Roger B. J. Benson (2015)
Peculiar macrophagous adaptations in a new Cretaceous pliosaurid.
Royal Society Open Science 2: 150552
During the Middle and Late Jurassic, pliosaurid plesiosaurs evolved
gigantic body size and a series of craniodental adaptations that have
been linked to the occupation of an apex predator niche. Cretaceous
pliosaurids (i.e. Brachaucheninae) depart from this morphology, being
slightly smaller and lacking the macrophagous adaptations seen in
earlier forms. However, the fossil record of Early Cretaceous
pliosaurids is poor, concealing the evolution and ecological diversity
of the group. Here, we report a new pliosaurid from the Late
Hauterivian (Early Cretaceous) of Russia. Phylogenetic analyses using
reduced consensus methods recover it as the basalmost brachauchenine.
This pliosaurid is smaller than other derived pliosaurids, has tooth
alveoli clustered in pairs and possesses trihedral teeth with complex
serrated carinae. Maximum-likelihood ancestral state reconstruction
suggests early brachauchenines retained trihedral teeth from their
ancestors, but modified this feature in a unique way, convergent with
macrophagous archosaurs or sphenacodontoids. Our findings indicate
that Early Cretaceous marine reptile teeth with serrated carinae
cannot be unequivocally assigned to metriorhynchoid crocodylomorphs.
Furthermore, they extend the known diversity of dental adaptations
seen in Sauropterygia, the longest lived clade of marine tetrapods.