A New Palatine for Askeptosaurus
Askeptosaurus italicus (Nopcsa 1925) Middle Triassic ~225 mya, ~2 m long, is known from several crushed, largely complete skeletons. It was a mesosaur/thalattosaur derived from a sister to Stereosternum, Wumengosaurusand Xinpusaurus and phylogenetically preceded other thalattosauriformes, such as Miodentosaurus and Endennasaurus.
Müller (2005) reported, “The palatine is only poorly preserved. In specimen PIMUZ T 4846 (Fig. 5A), the posterolateral portion is exposed [in dorsal view] slightly in the anterior half of the left orbit. It possesses a concave posterior margin, which indicates that the palatine formed the anterior border of the suborbital fenestra.“ Müller did not identify a palatine in PIMUZ T4832, a skull preserved in ventral (palatal) view.
Figure 1. Click to enlarge. The palatine of Askeptosaurus. Upper left: Reconstruction by Müller 2005 with a generic palatine identified. Upper right: insitu ventral view of PMIZ with overlooked palatine colored violet. Upper right inset: palatine identified by Müller 2005 in anterior orbit in dorsal view, PMIZ. Lower left reconstruction with new palatine in place. Lower right: Clarazia palate with palatine identified in violet.
Let’s Look for Palatines in Related Taxa
Clarazia provides a clear palatine, a ‘Y’-shaped element in the anterior palate. A similar structure was traced by Müller 2005 but not recognized as a palatine. It’s a match for the palatine in Clarazia and a perfect fit against the rim of the pterygoid.
We’ll look at a series of enaliosaurian (Sauropterygia + Ichthyopterygia + Thalattosauriformes) palates next time.
As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.
Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.
References
Nopcsa F 1925. Askeptosaurus, ein neues reptil der Trias von Besano: Centralblatt für Mineralogie, Geologie und Paläontologie, p. 265-2
Kuhn E 1952. Die Triasfauna der Tessiner Kalkalpen. XVII. Askeptosaurus italicus Nopsca. Abhandlungen der Schweizerischen Paläontologischen Gesellschaft, 69, 1–73.
Kuhn-Schnyder E 1971. Über einen Schädel von Askeptosaurus italicus Nopcsa aus der Mittleren Trias des Monte San Giorgio (Kt Tessin, Schweiz). Abhandlungen des Hessischen Landesamtes für Bodenforschung, 60, 89–98
Müller J 2005. The anatomy of Askeptosaurus italicus from the Middle Triassic of Monte San Giorgio and the interrelationships of thalattosaurs (Reptilia, Diapsida). Canadian Journal of Earth Science 42: 1347–1367.
2012-09-20 00:23:24
Source: http://pterosaurheresies.wordpress.com/2012/09/19/a-new-palate-for-askeptosaurus/
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