[dinosaur] Pseudotherium, new mammaliamorph from Triassic Ischigualasto Formation of Argentina (free pdf)

Ben Creisler
[email protected]

A new paper in open access:

Pseudotherium argentinus gen. et. sp. nov.

NOTE: "therium" is neuter so "argentinum" is the correct spelling here...

Rachel V. S. Wallace, Ricardo Martínez & Timothy Rowe (2019)
First record of a basal mammaliamorph from the early Late Triassic
Ischigualasto Formation of Argentina.
PLoS ONE 14(8): e0218791.
doi:  https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1371_journal.pone.0218791&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=kWYERzR1DfBiGqzePPSAVsFtwTPF02kRiJ9m1bqSHRg&s=m-bnaf_6eOp-9u-3CLPEVSUhQ6lBj0WoFR03Vg1FTP0&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__journals.plos.org_plosone_article-3Fid-3D10.1371_journal.pone.0218791&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=kWYERzR1DfBiGqzePPSAVsFtwTPF02kRiJ9m1bqSHRg&s=eMfJE1DrS4esVO1IVNyfoXNB5DPhT17OfVpgpzeT6LE&e= 

Free pdf:
https://urldefense.proofpoint.com/v2/url?u=https-3A__journals.plos.org_plosone_article_file-3Fid-3D10.1371_journal.pone.0218791-26type-3Dprintable&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=kWYERzR1DfBiGqzePPSAVsFtwTPF02kRiJ9m1bqSHRg&s=3SelRPs7fsXQx2NLTL6omqEAANG9TIUdJsTc8wbhYBE&e= 


We describe a new probainognathian cynodont, Pseudotherium argentinus, from
the early Late Triassic Ischigualasto Formation of Argentina. Pseudotherium
adds to a growing assemblage of small Triassic cynodonts that offers new
insight into events leading up to the origin of crown Mammalia and the
successively more inclusive Mammaliaformes and Mammaliamorpha. Using
high-resolution X-ray computed tomography, we illustrate and describe the
holotype and only known specimen, which consists of a well-preserved
isolated skull. It preserves apomorphic features of the orbit and
braincase. Prefrontal and vestigial postorbital bones are present, despite
the absence of an ossified postorbital bar. As in Brasilitherium
riograndensis, thin turbinal-like bones are present in the nasopharyngeal
passage, and we discuss impediments to establishing their identity and
function. Compared to more basal cynodonts, the cochlea is elongated but
uncoiled and in this and other features it resembles basal mammaliamorphs.
Our analysis found weak support for Pseudotherium as the sister taxon of
Tritylodontidae. However, a broader assessment of its relationships in
light of additional character data from the literature and unpublished
computed tomography data suggest that it may be more realistic to view the
relationships of Pseudotherium as an unresolved polytomy with
tritylodontids, and the taxa referred to as tritheledontids and
brasilodontids (groups of variable membership and questionable monophyly).
Thus, Pseudotherium may lie just inside or just outside of Mammaliamorpha,
and there is also weak character support for its sister taxon relationship
with Brasilitherium. Our results amplify previous conclusions that
phylogenetic relationships in this adaptive radiation of small cynodonts
will remain somewhat uncertain until more complete specimens are recovered,
and until high-resolution CT scans of existing specimens become available
to the larger community. Toward that goal, we make the CT dataset for the
holotype of Pseudotherium argentinus publically available under a Creative
Commons license at www.DigiMorph.org.




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