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New papers online for Acta Palaeontologica Polonica

From: Ben Creisler

New papers online for Acta Palaeontologica Polonica

With the new oviraptor Machairasaurus leptonychus just 
posted in the September issue of Palaeontology, the Sept. 
JVP now online, and the review of tyrannosaurs in the new 
issue  Science, it's becoming a red letter day for 
dinosaurs. In case these have not been mentioned, the 
forthcoming papers section of Acta Palaeontologica 
Polonica posted some new dinosaur-related papers. The 
pdfs are free, of course.

The teeth of the unenlagiine theropod Buitreraptor from 
the Cretaceous of Patagonia, Argentina, and the unusual 
dentition of the Gondwanan dromaeosaurids 
Federico A. Gianechini, Peter J. Makovicky, and Sebastián 

Acta Palaeontologica Polonica in press
available online 16 Sep 2010

The Unenlagiinae is a clade of Gondwanan dromaeosaurid 
theropods mainly known from incomplete skeletal material. 
The group includes two recently discovered theropods, 
Buitreraptor and Austroraptor, from which cranial remains 
are available with in situ maxillary and dentary teeth, 
thus allowing the study of tooth morphology. Among the 
derived traits that diagnose the dentition of 
unenlagiines are: 1) high tooth count, 2) small size of 
individual teeth when compared with skull height, 3) 
absence of denticles and carinae, and 4) presence of 
longitudinal grooves on the tooth crown. This suite of 
dental characteristics, shared between Buitreraptor and 
Austroraptor, can be considered as diagnostic of the 
Unenlagiinae or, at least, a more exclusive clade within 
the group. The teeth of Buitreraptor exhibit a remarkable 
labiolingual compression, whereas Austroraptor possesses 
more conical teeth, probably respective autapomorphic 
features. On one hand, these dental morphologies differ 
from those observed in most Laurasian dromaeosaurids and, 
for instance, could be considered as further proof of the 
purported vicariant evolution of the lineage on the 
southern continents. On the other hand, the morphological 
similarities (e.g. absence of denticles) between the 
teeth of unenlagiines and other theropod lineages, 
including Mesozoic birds and ornithomimosaurs, can be 
considered as the result of parallel trends related to 
dental reduction.


New remains attributable to the holotype of the sauropod 
dinosaur Neuquensaurus australis, with implications for 
saltasaurine systematics
Michael D. D?Emic and Jeffrey A. Wilson

Acta Palaeontologica Polonica in press
available online 14 Sep 2010

The Late Cretaceous South American sauropods 
Neuquensaurus australis and Saltasaurus loricatus are 
represented by well-preserved and abundant material that 
has been integral to our understanding of titanosaur 
anatomy for decades. Although the hypodigms for these 
species span most of the skeleton, holotypic materials 
are limited to a few bones that do not overlap between 
the two taxa.
In this contribution, we augment the holotype of 
Neuquensaurus australis with a partial sacrum that was 
preserved in articulation with one of the original caudal 
vertebrae described by Lydekker (1893), but not 
recognized as such at the time. We document this field 
association via the presence of a broken piece of matrix 
on the sixth sacral vertebral centrum that has a snap-fit 
to matrix on the rim of the anterior condyle of the 
holotypic biconvex vertebra. Based on comparisons with a 
more complete sacrum and ilium of a referred specimen of 
Neuquensaurus australis, we interpret this biconvex 
vertebra to be the seventh sacral vertebra. This raises 
the possibility that the biconvex ?first caudal? vertebra 
of some other titanosaurs may be part of the sacrum as 
Augmentation of the Neuquensaurus australis holotype to 
include a sacrum makes it directly comparable to the 
holotype of Saltasaurus loricatus. Morphological 
differences in the number, shape, and proportion of 
sacral vertebrae allow discrimination between 
Neuquensaurus and Saltasaurus, confirming their generic 
separation. The El Brete quarry, which preserves the 
holotypic sacrum and abundant referred specimens of 
Saltasaurus loricatus, also preserves a sacrum consisting 
of seven vertebrae that bears autapomorphies of 
Neuquensaurus australis, indicating that these two 
saltasaurines coexisted.



The extent of the pterosaur flight membrane
Ross A. Elgin, David W.E. Hone, and Eberhard Frey

Acta Palaeontologica Polonica in press
available online 14 Sep 2010

The shape and extent of the membranous brachioptagium in 
pterosaurs remains a controversial topic for those 
attempting to determine the aerodynamic performance of 
the first vertebrate fliers. Various arguments in favour 
of the trailing edge terminating against either the torso 
or hip, the femur, the ankle, or different locations for 
various taxa, has resulted in several published 
reconstructions. Uncertainty over the correct model is 
detrimental to both aerodynamic and palaeoecological 
studies that are forced to simultaneously consider 
multiple and highly variable configurations for 
individual taxa. A review of relevant pterosaur specimens 
with preserved soft tissues or impressions of the wing 
membrane, however, strongly suggests that the trailing 
edge of the wing extended down to the lower leg or ankle 
in all specimens where the brachiopatagium is completely 
preserved. This configuration is seen across a 
phylogenetically broad range of pterosaurs and is thus 
likely to have been universally present throughout the 
Pterosauria. Support for opposing hypotheses where the 
trailing edge terminates against the body, hip, or knee 
are based on several specimens where the wing membrane is 
either incomplete or has undergone post-mortem 
contraction. An ankle attachment does not rule out a high 
aspect ratio wing as the curvature of the trailing edge 
and the ratio of the fore to hind limbs also play a major 
role in determining the final shape of the membrane.