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Palaeoxonodon, mammal from Middle Jurassic of Scotland + Simoliophis, snake from Cretaceous of France



Ben Creisler
bcreisler@gmail.com

Two new non-dino papers:

Roger A. Close, Brian M. Davis, Stig Walsh, Andrzej S. Wolniewicz,
Matt Friedman and Roger B. J. Benson (2015)
A lower jaw of Palaeoxonodon from the Middle Jurassic of the Isle of
Skye, Scotland, sheds new light on the diversity of British stem
therians.
Palaeontology (advance online publication)
DOI: 10.1111/pala.12218
http://onlinelibrary.wiley.com/doi/10.1111/pala.12218/abstract

Data for this study are available in the Dryad Digital Repository:
http://dx.doi.org/10.5061/dryad.52582

The Middle Jurassic was a key interval of mammalian evolutionary
history that witnessed the diversification of the therian stem group.
Great Britain has yielded a significant record of mammalian fossils
from this interval, represented by numerous isolated jaws and teeth
from the Bathonian of Oxfordshire and the Isle of Skye. This record
captures a key period in early cladotherian evolution, with
amphitheriids, peramurans and ‘stem zatherians’ displaying
intermediate talonid morphologies that document the evolutionary
assembly of tribosphenic molars. We present a mandible with
near-complete dentition from the late Bathonian (c. 167.4–166.5 Ma)
Kilmaluag Formation, near Elgol, Skye, representing the amphitheriid
Palaeoxonodon ooliticus, previously known only from isolated teeth.
The specimen sheds new light on the taxonomic diversity of British
Middle Jurassic stem therians, as the morphological variation within
the preserved tooth row encompasses that previously ascribed to three
distinct species within two genera: Palaeoxonodon ooliticus, P.
freemani and Kennetheridium leesi. Thus, both P. freemani and K. leesi
are subjective junior synonyms of P. ooliticus. The dental formula of
P. ooliticus (i4:c1:p5:m5) is intermediate between the primitively
larger postcanine count (p5:m6–7) of Amphitherium and the reduced
number in peramurans and tribosphenidans (p5:m3). Phylogenetic
analyses of P. ooliticus generally confirm a close affinity with
Amphitherium, but highlight the lack of strong empirical support for
hypothesized patterns of divergences among early cladotherians.


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Jean-Claude Rage, Romain Vullo & Didier Néraudeau (2016)
The mid-Cretaceous snake Simoliophis rochebrunei Sauvage, 1880
(Squamata: Ophidia) from its type area (Charentes, southwestern
France): Redescription, distribution, and palaeoecology.
Cretaceous Research 58: 234-253
doi:10.1016/j.cretres.2015.10.010
http://www.sciencedirect.com/science/article/pii/S0195667115300896


Highlights

The Cenomanian snake Simoliophis rochebrunei is diagnosed and redescribed.
S. rochebrunei is a marine snake that likely had posterior legs.
In its type area (Charentes), this species is restricted to the lower
Cenomanian.
Its palaeoecology and a peculiar morphofunctional aspect are discussed.

Abstract

Simoliophis rochebrunei is a snake restricted to the Cenomanian of
southwestern Europe. It is the type species of the genus Simoliophis,
the latter being the type genus of the Simoliophiidae, i.e. the family
that is comprised of the marine hindlimbed snakes. The first
descriptions of the species were insufficient and dealt only with
mid-trunk vertebrae, whereas vertebrae from other parts of the
vertebral column are markedly different from the latter.
Paradoxically, species subsequently included in the genus are better
known than the type species. In the present article, S. rochebrunei is
described and diagnosed on the basis of material found recently in the
type area (Charentes, southwestern France). Strong pachyostosis
affects the mid-trunk and the anterior portion of the posterior trunk
region. A part of the vertebral column affected by pachyostosis was
more or less stiff. As with all pachyostotic squamates, S. rochebrunei
was aquatic; it lived in shallow marine water, whose bottom was sandy,
but it was also able to enter brackish environments. It was a slow
swimmer capable of shallow, but long dives. The species may be used as
a stratigraphic marker since it is restricted to the lower Cenomanian
in the type area.