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Dinosaur-related papers in new JVP: tails, Dysalotosaurus braincase, Sapeornis



From: Ben Creisler
bcreisler@gmail.com

The new issue of the Journal of Vertebrate Paleontology is out online at:
http://www.tandfonline.com/toc/ujvp20/current


There are a number of papers about dinosaurs, marine reptiles, and
other Mesozoic critters. Starting with the dinosaur papers:

David W. E. Hone (2012)
Variation in the tail length of non-avian dinosaurs.
Journal of Vertebrate Paleontology 32 (5): 1082-1089
DOI:10.1080/02724634.2012.680998
http://www.tandfonline.com/doi/abs/10.1080/02724634.2012.680998



Estimating the mass of an extinct organism is naturally difficult.
Practicality and simplicity means that often some linear measurement
is used as a proxy. In the case of non-avian dinosaurs, the total
length of the animal (from the snout to the tip of the tail) is
sometimes used for this purpose. However, the total length of the tail
is unknown in all but very few dinosaurian taxa. Tail length data
taken from specimens and the literature are shown here to have
remarkable variation both between and within clades (and even within
single species). Comparison with body length data shows that total
length (including the tail) is therefore a less reliable measure of
size than using the snout-vent length of the animal. ‘Snout-sacrum’
lengths are suggested as a more reliable alternative. Total length
should not be abandoned, however, both to provide a comparison with
older works and specimens lacking complete presacral axial columns,
and for communication with the general public.


===


Gabriela Sobral, Christy A. Hipsley & Johannes Müller (2012)
Braincase redescription of Dysalotosaurus lettowvorbecki (Dinosauria,
Ornithopoda) based on computed tomography.
Journal of Vertebrate Paleontology 32 (5): 1090-1102
DOI:10.1080/02724634.2012.693554
http://www.tandfonline.com/doi/abs/10.1080/02724634.2012.693554

Computed tomography (CT) has become a major tool to elucidate the
anatomy of fossil taxa, including the braincase and inner ear.
However, sample size is still limited and studies have concentrated
mainly on saurischian dinosaurs. Here we report on the braincase
anatomy of the Upper Jurassic ornithopod Dysalotosaurus using
high-resolution X-ray micro-CT (μCT). The main trunk of the vena
capitis dorsalis was found between the parietal and supraoccipital,
leading to a nomenclatural revision of cephalic veins and
reidentification of their bony correlates. Contrary to the condition
in hadrosaurid ornithischians, the posterior semicircular canal is the
shortest canal in Dysalotosaurus, whereas the lateral is the longest,
lying dorsal to the vestibule, as in basal archosaurs. The
anteroventral inclination of the lateral semicircular canal suggests
that Dysalotosaurus must have oriented its head dorsally while alert.
Because the cochlea is relatively short, Dysalotosaurus had reduced
ability to discriminate between high- and low-frequency sounds, as in
sauropods, basal ceratopsians, and other basal archosaurs. The metotic
foramen, however, was fully subdivided into a fenestra pseudorotunda
and a vagus foramen, a derived character for archosaurs that is
usually associated with a more refined sense of hearing. Lack of a
refined capacity for discrimination of sound frequencies due to a
short cochlea together with the equal-sized and thick semicircular
canals represent plesiomorphic characters for Dinosauria. The middle
and inner ears of Dysalotosaurus bear a mosaic of primitive and
derived features, pointing to a more complex evolutionary history of
these structures.


===



Chunling Gao, Luis M. Chiappe, Fengjiao Zhang, Diana L. Pomeroy,
Caizhi Shen, Anusuya Chinsamy & Maureen O. Walsh (2012)
A subadult specimen of the Early Cretaceous bird Sapeornis
chaoyangensis and a taxonomic reassessment of sapeornithids.
Journal of Vertebrate Paleontology 32 (5):  1103-1112
DOI:10.1080/02724634.2012.693865
http://www.tandfonline.com/doi/abs/10.1080/02724634.2012.693865


We describe the anatomy and bone microstructure of a new subadult
specimen of Sapeornis chaoyangensis from the Early Cretaceous of
Liaoning Province, China. To date, this is the only known sapeornithid
that preserves substantial portions of its plumage. Found in the
Yixian Formation, it also represents the oldest known sapeornithid,
and as such, extends the stratigraphic range of this lineage 3–5
million years. This specimen also increases our knowledge of
sapeornithid skeletal and integumentary anatomy, including previously
unrecognized details of the primary and secondary wing feathers.
Examination of the characters used to diagnose other named
sapeornithid species reveals that such diagnoses have incorporated
morphologies that are influenced by either taphonomy or ontogeny.
Based on qualitative and quantitative comparisons between the new
specimen and other sapeornithid species, we argue that all other named
sapeornithids are junior synonyms of S. chaoyangensis.


====

Plus some dinosaur material from the Triassic of Poland:


Tomasz Sulej, Grzegorz Niedźwiedzki & Robert Bronowicz (2012)
A new Late Triassic vertebrate fauna from Poland with turtles,
aetosaurs, and coelophysoid dinosaurs.
Journal of Vertebrate Paleontology 23 (5): 1033-1041
DOI:10.1080/02724634.2012.694384
http://www.tandfonline.com/doi/abs/10.1080/02724634.2012.694384

We report a new site with an occurrence of isolated bones of a
Palaeochersis-like turtle in Norian-Rhaetian fluvial sediments from
southern Poland. The turtle remains are associated with bones of a
medium-sized aetosaur, a coelophysoid dinosaur, and a larger
carnivorous archosaur, as well as a hybodontid shark, ganoid and
dipnoan fishes, and a large temnospondyl.