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Non-Dino Papers: Palaeozoic and Triassic stuff

From: Ben Creisler

Some recent papers about non-dinosaur taxa and topics that might be of interest:


Marianne R. Pearson, Roger B.J. Benson, Paul Upchurch, Jörg Fröbisch &
Christian F. Kammerer (2012)
Reconstructing the diversity of early terrestrial herbivorous tetrapods.
Palaeogeography, Palaeoclimatology, Palaeoecology (advance online publication)
doi: http://dx.doi.org/10.1016/j.palaeo.2012.11.008

Terrestrial herbivorous tetrapods first appear in the fossil record
during the Late Carboniferous (306.5 Ma). The diversification of
herbivores is a key aspect of the transition to the modern trophic
structure of terrestrial vertebrate ecosystems, because it allowed
tetrapods to exploit terrestrial (i.e. non-aquatic) primary
productivity. However, the palaeodiversity dynamics of the earliest
terrestrial vertebrate herbivores have received relatively little
attention, apart from a few studies that focus on specific clades. A
new data set containing 287 species occurrences of herbivorous
tetrapods including the major Palaeozoic and Early Triassic clades
Anomodontia, Archosauromorpha, Bolosauridae, Captorhinidae, Caseidae,
Cynodontia, Dinocephalia, Diadectomorpha, Edaphosauridae,
Pareiasauria, Poposauroidea, Procolophonoidea, Rhynchosauria,
Silesauridae and Therocephalia is used to analyse palaeodiversity from
the Late Carboniferous to the Middle Triassic (~ 306.5 – ~ 236 Ma),
taking into account the effects of potential sampling biases by using
the number of tetrapod-bearing formations as a proxy. The results
support a gradual increase in taxic diversity from the Late
Carboniferous to the Wordian, followed by a dip in diversity during
the Guadalupian (Middle Permian), and an increase to a peak in the
Late Permian at the Wuchiapingian/Changhsingian boundary. Herbivorous
tetrapods were strongly affected by the end-Permian mass extinction
with both the herbivorous Pareiasauria and Captorhinidae becoming
extinct and the observed number of anomodont species decreasing by up
to 80%. The drop in observed diversity at the end Permian is dampened
slightly because of the radiation of new herbivorous forms during the
Early Triassic. A strong biological signal is apparent even after
correcting for sampling.


► Gradual rise in diversity of herbivorous tetrapods
► Two Permian drops in diversity
► Strong biological signal even after correcting for sampling


Nicholas Fordyce, Roger Smith & Anusuya Chinsamy (2012)
Evidence of a therapsid scavenger in the Late Permian Karoo Basin, South Africa.
South African Journal of Sciencel 108 (11/12)
doi: 10.4102/sajs.v108i11/12.1158
NOTE: pdf is free

Dicynodonts are an extinct group of herbivorous non-mammalian
therapsids (‘mammal-like’ reptiles) that are widely known from
terrestrial Permo-Triassic strata throughout Pangaea. Dicynodont
fossil remains are common within the Late Permian Beaufort Group of
the Karoo Basin in South Africa. A large, partially articulated
dicynodont skeleton recovered from the Tropidostoma Assemblage Zone is
taphonomically important in having an unusual disarticulation pattern,
bone surface punctures and a broken tooth of an unidentified carnivore
associated with it. Here we report on the nature of the bone damage,
and the identity of the carnivore that lost a canine tooth whilst
scavenging the dicynodont carcass. The morphological characteristics
of the serrations on the unidentified tooth were compared with those
of contemporaneous carnivores, the gorgonopsians and therocephalians.
Scanning electron microscopy analysis of a silicone cast of the
unidentified tooth revealed distinctive 0.5-mm square-shaped
serrations. Our comparative assessment of the tooth size, curvature,
cross-sectional shape and morphology of the serrations revealed that
the unidentified canine most closely matched Aelurognathus, a
gorgonopsian known from the same assemblage zone.


Tobias Nasterlacka, Aurore Canovillea & Anusuya Chinsamya (2012)
New insights into the biology of the Permian genus Cistecephalus
(Therapsida, Dicynodontia).
Journal of Vertebrate Paleontology 32(6):1396-1410

The taxonomy and paleobiology of the Upper Permian dicynodont
Cistecephalus have been much debated over the last century. Fossils of
Cistecephalus have been identified as belonging either to one species
or up to six species and hypotheses concerning their lifestyle range
from aquatic to arboreal and fossorial. Earlier studies of
Cistecephalus focused mainly on macroanatomical characteristics,
whereas the current assessment examines a combination of anatomical
features, as well as bone histology and microanatomy to unravel its
biology. The allometries of a skull growth series that were examined
in the present study imply that all Cistecephalus specimens belong to
a single species. Furthermore, our data suggest that the variability
in the occurrence of supraorbital ridges, which are raised in some
specimens and leveled in others, is a feature of sexual dimorphism.
Histological thin-sections of a humerus, an ulna, a femur, and ribs
from two Cistecephalus specimens were studied to evaluate life history
traits of this taxon. The comparison of ribs from a subadult and a
fully grown specimen allows an estimation that sexual maturity was
attained when the skull length was between 5.9 and 6.5 cm. The compact
microstructure of the sampled Cistecephalus bones implies aquatic
and/or fossorial adaptations, refuting an arboreal lifestyle. We
propose that the high degree of binocular vision evident in
Cistecephalus developed in response to predatory (insectivory) and/or
nocturnal habits and that it is unrelated to a scansorial lifestyle.


Leandro C. Gaetano, Helke Mocke, Fernando Abdala & P. John Hancox (2012)
Complex multicusped postcanine teeth from the Lower Triassic of South Africa.
Journal of Vertebrate Paleontology 32(6):1411-1420

Two incisors and five postcanine teeth of complex crown morphology
were found in the lower levels of the Burgersdorp Formation of the
Beaufort Group, corresponding to the basal Subzone A of the
Cynognathus Assemblage Zone (late Olenekian). All the teeth bear a
single root and the postcanines show two rows of mesiodistally aligned
cusps and a central basin or groove. Among the postcanines, two
general patterns of crown morphology are recognized on the basis of
relative length of the cusp rows, number of cusps per row, and width
of the central area. Phylogenetic affinities of the described
specimens remain unclear, and thus they are regarded as Eucynodontia
incertae sedis. However, comparisons with non-mammalian cynodonts with
labiolingually expanded postcanines show that they are most similar to
those of Aleodon, Candelariodon, and some haramiyids. Many cynodont
taxa such as Aleodon, Candelariodon, Cromptodon, haramiyids, and
tritylodontids, which are probably not closely related to each other,
have labiolingually expanded postcanines with cusps arranged
mesiodistally in rows and a central basin; thus pointing to the
homoplastic nature of dental morphologies in the cynodont lineage. The
teeth presented here are the oldest record of therapsid teeth with
crowns having parallel rows of cusps, representing a temporal
extension of approximately 10 million years for this crown pattern.


Jörg Fröbisch (2012)
Vertebrate diversity across the end-Permian mass extinction –
separating biological and geological signals.
Palaeogeography, Palaeoclimatology, Palaeoecology (advance online publication)
doi: http://dx.doi.org/10.1016/j.palaeo.2012.10.036

This study examines regional diversity patterns of Permian-Triassic
terrestrial vertebrates of the South African Karoo Basin and the
Russian fore-Ural region. Previous studies clearly established that
the diversity patterns of synapsids, the dominant terrestrial
tetrapods of their time, are significantly biased by heterogeneity in
the Permian-Triassic terrestrial rock record. This conclusion was
based on a positive correlation between taxonomic diversity estimates
(TDEs) and varying sampling proxies: (1) number of formations and (2)
outcrop area. Recently, these proxies have been criticized to be
non-independent variables or problematic for other reasons and (3)
number of localities or (4) number of specimens have been suggest as
more reliable proxies. In the present study, I test the relevance of
the latter proxies (2–4) with respect to vertebrate diversity in South
Africa and Russia. On these regional scales, log-transformed and
generalized differenced TDEs of vertebrates at varying taxonomic
levels are (with few exceptions) not significantly correlated with the
various sampling proxies (2–4) for the complete time series. After
eliminating the impact of the end-Permian extinction event by
excluding the earliest Triassic time intervals, selected vertebrate
TDEs in South Africa and Russia show statistically significant strong
positive correlations with outcrop area, number of localities, and
number of specimens. Diversity residuals, resulting from modeled
diversity estimates, exhibit clade-specific patterns with little
support for a mid-Permian (end-Guadalupian) event but strong support
for a severe end-Permian extinction. The results imply that, although
vertebrate diversity patterns in South Africa and Russia are at least
partially biased by the Permian-Triassic terrestrial rock record, they
still preserve genuine biological signals. Finally, it is important to
note that outcrop area represents a valid and useful sampling proxy at
the regional scale of the South African Karoo Basin and that it should
be used in concert with other sampling proxies, such as the number of
localities and specimens, that accurately capture various aspects of
sampling in a given study area, as it has been performed in the
present study.