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RE: On the subject of mysterious absences...The Answer
Nick Pharris wrote:
>> _Pseudocetorhinus_ is even older (Triassic). It was an elasmobranch
>> (maybe a synechodontiform).
> What about _Mesosaurus_ (Permian)?
The idea of filter-feeding mesosaurs was recently shot down I'm afraid...
Modesto, S.P. (2006) The cranial skeleton of the Early Permian aquatic reptile
_Mesosaurus tenuidens_: implications for relationships and palaeobiology
Zool. J. Linn. Soc. 146: 345-368.
Abstract: "The cranial osteology of the aquatic reptile _Mesosaurus tenuidens_
is redescribed on the basis of new and previously examined materials from the
Lower Permian of both southern Africa and South America. _Mesosaurus_ is
distinguished from other mesosaurs in exhibiting an absolutely larger skull and
possessing relatively longer marginal teeth. The teeth gradually angle
outwards as one progresses anteriorly in the tooth row and become conspicuously
procumbent at the tip of the snout. The suggestion that mesosaurs used their
conspicuous dental apparatus as a straining device for filter feeding is based
upon erroneous reconstruction of a high number of teeth in this mesosaur.
Reinterpretation of the morphology and the organization of the marginal teeth
of _Mesosaurus_ suggests that they were used to capture individually small,
nektonic prey. General morphological aspects of the skull support the idea
that _Mesosaurus_ was an aquatic predator and that the skull was well
adapted for feeding in an aqueous environment. The anatomical review permits
critical reappraisal of several cranial characters that have appeared in recent
phylogenetic analyses of early amniotes. Emendation of problematic characters
and reanalysis of amniote phylogeny using a slightly modified data matrix from
the literature strengthens the hypothesis that mesosaurs form a clade with
millerettids, procolophonoids and pareiasaurs within Reptilia."
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