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Dinilysia, Cretaceous snake (free pdf!)



From: Ben Creisler
bcreisler@gmail.com

This paper was out in advance online some time back but now is
available for free:




ZAHER, H. and SCANFERLA, C. A. (2012)
The skull of the Upper Cretaceous snake Dinilysia patagonica
Smith-Woodward, 1901, and its phylogenetic position revisited.
Zoological Journal of the Linnean Society, 164: 194–238.
doi: 10.1111/j.1096-3642.2011.00755.x
http://onlinelibrary.wiley.com/doi/10.1111/j.1096-3642.2011.00755.x/abstract



The cranial anatomy of Dinilysia patagonica, a terrestrial snake from
the Upper Cretaceous of Argentina, is redescribed and illustrated,
based on high-resolution X-ray computed tomography and better
preparations made on previously known specimens, including the
holotype. Previously unreported characters reinforce the intriguing
mosaic nature of the skull of Dinilysia, with a suite of plesiomorphic
and apomorphic characters with respect to extant snakes. Newly
recognized plesiomorphies are the absence of the medial vertical
flange of the nasal, lateral position of the prefrontal, lizard-like
contact between vomer and palatine, floor of the recessus scalae
tympani formed by the basioccipital, posterolateral corners of the
basisphenoid strongly ventrolaterally projected, and absence of a
medial parietal pillar separating the telencephalon and mesencephalon,
amongst others. We also reinterpreted the structures forming the otic
region of Dinilysia, confirming the presence of a crista
circumfenestralis, which represents an important derived ophidian
synapomorphy. Both plesiomorphic and apomorphic traits of Dinilysia
are treated in detail and illustrated accordingly. Results of a
phylogenetic analysis support a basal position of Dinilysia, as the
sister-taxon to all extant snakes. The fossil taxa Yurlunggur,
Haasiophis, Eupodophis, Pachyrhachis, and Wonambi appear as derived
snakes nested within the extant clade Alethinophidia, as stem-taxa to
the crown-clade Macrostomata. The hypothesis of a sister-group
relationship between Dinilysia and Najash rionegrina, as suggested by
some authors, is rejected by the results of our analysis.