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Utatsusaurus (Triassic ichthyopterygian) skull described



From: Ben Creisler
bcreisler@gmail.com


A paper in the new JVP:

Robin S. Cuthbertson, Anthony P. Russell & Jason S. Anderson (2013)
Reinterpretation of the cranial morphology of Utatsusaurus hataii
(Ichthyopterygia) (Osawa Formation, Lower Triassic, Miyagi, Japan) and
its systematic implications.
Journal of Vertebrate Paleontology 33(4):817-830
DOI:10.1080/02724634.2013.756495
http://www.tandfonline.com/doi/full/10.1080/02724634.2013.756495#.Ucnk8vm1FcQ

Utatsusaurus hataii is an early member of Ichthyopterygia from the
Osawa Formation (Lower Triassic) of Miyagi Prefecture, Japan. Although
the holotype of the species lacks a well-preserved cranium, UHR 30691
preserves a near-complete skull and may be referred to Utatsusaurus
based on a similar geologic occurrence and, most importantly, the
following shared features with the holotype: subthecodont tooth
implantation; the presence of distomesially compressed tooth crowns; a
humerus that is longer than wide; and an ulnar facet on the humerus
that is as wide as the radial facet. The first complete description of
the skull of UHR 30691 and the incorporation of data derived from it
into a phylogenetic analysis retrieves a monophyletic Ichthyopterygia
that is supported by 18 unambiguous synapomorphies. The updated
analysis recovers Utatsusaurus in a basal clade with Parvinatator
(united by one unambiguous feature), which collectively form the
sister group to all other ichthyopterygians.