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Paleorhinus and Ebrachosuchus (Triassic phytosaurs from Germany) redescribed



From: Ben Creisler
bcreisler@gmail.com

A new online paper:



Richard J. Butler, Oliver W. M. Rauhut, Michelle R. Stocker & Robert
Bronowicz (2013)
Redescription of the phytosaurs Paleorhinus (‘Francosuchus’)
angustifrons and Ebrachosuchus neukami from Germany, with implications
for Late Triassic biochronology.
Zoological Journal of the Linnean Society (advance online publication)
DOI: 10.1111/zoj.12094
http://onlinelibrary.wiley.com/doi/10.1111/zoj.12094/abstract


Phytosaurs are a diverse and morphologically distinctive clade of
superficially crocodile-like archosauriforms that had a near global
distribution during the Late Triassic. Because their remains are among
the most abundant vertebrate remains recovered in many Upper Triassic
terrestrial formations, phytosaurs are used extensively in long-range
biochronological and biostratigraphic correlations. The
biochronologically oldest and earliest branching known phytosaurs
include an array of nominal species from the early Late Triassic of
the United States, Germany, Poland, Morocco, and India that have been
synonymized within the genus Paleorhinus, and subsequently used to
define a global ‘Paleorhinus biochron’. However, recent phylogenetic
work suggested that the North American species previously referred to
Paleorhinus are paraphyletic. Here, we reassess the systematics and
anatomy of putative specimens of Paleorhinus from southern Germany.
Two well-preserved basal phytosaur skulls from the Blasensandstein
(Carnian) of Bavaria form the holotypes of Francosuchus angustifrons
and Ebrachosuchus neukami, both of which were synonymized with
Paleorhinus by previous workers. We demonstrate that Francosuchus
angustifrons shares unique synapomorphies with specimens referred to
Paleorhinus bransoni from the Late Triassic of Texas, and thus refer
the species to Paleorhinus. By contrast, the longirostrine
Ebrachosuchus is highly distinctive in morphology, and our new
cladistic analysis of Phytosauria demonstrates that it represents a
valid taxon that is more closely related to Phytosauridae than to
Paleorhinus. We provide the first autapomorphy-based support for a
monophyletic but restricted Paleorhinus (supported by a nodal row on
the jugal, and low paired ridges on the squamosal) and confirm that
previous broader conceptions of Paleorhinus are likely to be
paraphyletic.