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Simorhinella (therocephalian synapsid) morphology, Permian of South Africa + Naomichelys



Ben Creisler
bcreisler@gmail.com

In the new issue of the Journal of Paleontology:



Fernando Abdala, Christian F. Kammerer, Michael O. Day, Sifelani
Jirah, and Bruce S. Rubidge (2014)
Adult morphology of the therocephalian Simorhinella baini from the
middle Permian of South Africa and the taxonomy, paleobiogeography,
and temporal distribution of the Lycosuchidae.
Journal of Paleontology 88(6):1139-1153. 2014
doi: http://dx.doi.org/10.1666/13-186
http://www.bioone.org/doi/abs/10.1666/13-186

The Middle Permian tetrapod fauna of the South African Beaufort Group
is taxonomically diverse and includes representatives of all major
therapsid groups, including the earliest records of Eutheriodontia. In
the Middle Permian, eutheriodonts are represented mainly by large
therocephalians, which made up a large proportion of the vertebrate
predators in these faunas. Here we describe the skull and partial
skeleton of a large therocephalian from the uppermost Tapinocephalus
Assemblage Zone (AZ) of South Africa. A combination of features,
including the short snout, presence of three to four upper postcanines
and presence of teeth on the pterygoid processes, indicates that the
new specimen belongs to the earliest-diverging therocephalian family,
Lycosuchidae. The presence of a well-developed midline ridge on the
ventral surface of the vomer indicates that the new specimen can be
referred to Simorhinella baini, a species previously represented only
by a tiny juvenile skull. The new specimen forms the basis for a
taxonomic re-evaluation of the Lycosuchidae as well as of the
geographic and stratigraphic range of the family. We recognize two
valid species within the Lycosuchidae: the type species Lycosuchus
vanderrieti represented by five specimens and Simorhinella baini
represented by two specimens, with an additional 22 specimens
currently identifiable as Lycosuchidae incertae sedis. Lycosuchid
specimens range throughout the Tapinocephalus and Pristerognathus AZs;
specimens of Simorhinella are restricted to the Tapinocephalus AZ,
whereas Lycosuchus specimens are documented in both the Tapinocephalus
and Pristerognathus AZs.





******

Walter G. Joyce, Juliana Sterli, and Sandra D. Chapman (2014)
The skeletal morphology of the solemydid turtle Naomichelys speciosa
from the Early Cretaceous of Texas.
Journal of Paleontology 88(6): 1257-1287
doi: http://dx.doi.org/10.1666/14-002
http://www.bioone.org/doi/abs/10.1666/14-002

The fossil record of solemydid turtles is primarily based on isolated
fragments collected from Late Jurassic to Late Cretaceous sediments
throughout North America and Europe and little is therefore known
about the morphology and evolutionary history of the group. We here
provide a detailed description of the only known near-complete
solemydid skeleton, which was collected from the Lower Cretaceous
(Aptian–Albian) Antlers Formation of Texas during the mid-twentieth
century, but essentially remains undescribed to date. Though
comparison is limited, the skeleton is referred to Naomichelys
speciosa, which is based on an isolated entoplastron from the Lower
Cretaceous (Aptian–Albian) Kootenai (Cloverly) Formation of Montana.
The absence of temporal emarginations, contribution of the jugals to
the orbits, and a clear subdivision of the middle and inner cavities,
and the presence of elongate postorbitals, posteriorly expanded
squamosals, a triangular fossa at the posterior margin of the
squamosals, an additional pair of tubercula basioccipitale that is
formed by the pterygoids, foramina pro ramo nervi vidiani (VII) that
are visible in ventral view, shell sculpturing consisting of high
tubercles, a large entoplastron with entoplastral scute, V-shaped
anterior peripherals, and limb osteoderms with tubercular sculpture
diagnose Naomichelys speciosa as a representative of Solemydidae. The
full visibility of the parabasisphenoid complex in ventral view, the
presence of an expanded symphyseal shelf, and the unusual ventromedial
folding of the coronoid process are the primary characteristics that
distinguish Naomichelys speciosa from the near-coeval European taxon
Helochelydra nopcsai.