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Clevosaurus (sphenodontian) from Brazil + Orobates (diadectid) skeleton + stegocephalian histology



Ben Creisler
bcreisler@gmail.com

A number of recent non-dino papers that may be of interest:

Annie Schmaltz Hsiou, Marco Aurélio Gallo De França & Jorge Ferigolo (2015)
New Data on the Clevosaurus (Sphenodontia: Clevosauridae) from the
Upper Triassic of Southern Brazil.
PLoS ONE 10(9): e0137523.
doi:10.1371/journal.pone.0137523
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0137523

The sphenodontian fossil record in South America is well known from
Mesozoic and Paleogene deposits of Argentinean Patagonia, mainly
represented by opisthodontians, or taxa closely related to the modern
Sphenodon. In contrast, the Brazilian fossil record is restricted to
the Caturrita Formation, Late Triassic of Rio Grande do Sul,
represented by several specimens of Clevosauridae, including
Clevosaurus brasiliensis Bonaparte and Sues, 2006. Traditionally,
Clevosauridae includes several Late Triassic to Early Jurassic taxa,
such as Polysphenodon, Brachyrhinodon, and Clevosaurus, the latter
well-represented by several species. The detailed description of the
specimen MCN-PV 2852 allowed the first systematic revision of most
Clevosaurus species. Within Clevosauridae, Polysphenodon is the most
basal taxon, and an IterPCR analysis revealed Brachrhynodon as a
possible Clevosaurus; C. petilus, C. wangi, and C. mcgilli as possibly
distinct taxonomic entities; and the South African Clevosaurus sp. is
not closely related to C. brasiliensis. These data indicate the need
of a deep phylogenetic review of Clevosauridae, in order to discover
synapomorphic characters among the diversity of these
Triassic/Jurassic sphenodontians.


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John A. Nyakatura , Vivian R. Allen, Jonas Lauströer, Amir Andikfar,
Marek Danczak, Hans-Jürgen Ullrich, Werner Hufenbach, Thomas Martens,
Martin S. Fischer (2015)
A Three-Dimensional Skeletal Reconstruction of the Stem Amniote
Orobates pabsti (Diadectidae): Analyses of Body Mass, Centre of Mass
Position, and Joint Mobility.
PLoS ONE 10(9): e0137284.
doi:10.1371/journal.pone.0137284
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0137284

Orobates pabsti, a basal diadectid from the lower Permian, is a key
fossil for the understanding of early amniote evolution. Quantitative
analysis of anatomical information suffers from fragmentation of
fossil bones, plastic deformation due to diagenetic processes and
fragile preservation within surrounding rock matrix, preventing
further biomechanical investigation. Here we describe the steps taken
to digitally reconstruct MNG 10181, the holotype specimen of Orobates
pabsti, and subsequently use the digital reconstruction to assess body
mass, position of the centre of mass in individual segments as well as
the whole animal, and study joint mobility in the shoulder and hip
joints. The shape of most fossil bone fragments could be recovered
from micro-focus computed tomography scans. This also revealed
structures that were hitherto hidden within the rock matrix. However,
parts of the axial skeleton had to be modelled using relevant isolated
bones from the same locality as templates. Based on the digital
fossil, mass of MNG 10181 was estimated using a model of body shape
that was varied within a plausible range to account for uncertainties
of the dimension. In the mean estimate model the specimen had an
estimated mass of circa 4 kg. Varying of the mass distribution amongst
body segments further revealed that Orobates carried most of its
weight on the hind limbs. Mostly unrestricted joint morphology further
suggested that MNG 10181 was able to effectively generate propulsion
with the pelvic limbs. The digital reconstruction is made available
for future biomechanical studies.


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Dorota Konietzko-Meier, Christen D. Shelton & P. Martin Sander (2015)
The discrepancy between morphological and microanatomical patterns of
anamniotic stegocephalian postcrania from the Early Permian Briar
Creek Bonebed (Texas).
Comptes Rendus Palevol (advance online publication)
doi:10.1016/j.crpv.2015.06.005
http://www.sciencedirect.com/science/article/pii/S1631068315001189



The histological framework of thirteen Early Permian tetrapod long
bones from a single locality, the Briar Creek Bonebed in Archer
County, Texas, USA, is described from a series of transverse sections
through the midshafts. The bones were morphologically categorized and
belong to one of three taxa: Eryops, Archeria, and Diadectes. However,
five histotypes are recognized. The first category includes the
juvenile bone. The second histotype is characterized by the presence
of radial vascular canals. The third histotype is characterized by the
numerous longitudinal canals arranged in regular rows. In the fourth
histotype, there is strong remodeling in the deep part of the cortex,
creating a distinct border with the external layer of lamellar bone.
In the fifth histotype, the deep part of the cortex is progressively
remodeled towards osteoporosis with distinct layers of large
circumferentially arranged erosion cavities. For femora and humeri,
histotypes match morphology. Histotype II is characteristic for
Diadectes propodials, histotype III is characteristic for Eryops
propodials, and histotype IV is characteristic for Archeria
propodials. A discrepancy between morphology and histology is observed
in the ulnae, fibula and radius. This discrepancy may be explained by
interspecific or intraspecific variability.