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Caudipteryx not a bird and more from APP



Dyke, G.J. and Norell, M.A. 2005. Caudipteryx as a non?avialan theropod
rather than a flightless bird. Acta Palaeontologica Polonica 50 (1):
101-116.

Caudipteryx zoui is a small enigmatic theropod known from the Early
Cretaceous Yixian Formation of the People's Republic of China. From the time
of its initial description, this taxon has stimulated a great deal of
ongoing debate regarding the phylogenetic relationship between non?avialan
theropods and birds (Avialae) because it preserves structures that have been
uncontroversially accepted as feathers (albeit aerodynamically unsuitable
for flight). However, it has also been proposed that both the relative
proportions of the hind limb bones (when compared with overall leg length),
and the position of the center of mass in Caudipteryx are more similar to
those seen in extant cusorial birds than they are to other non-avialan
theropod dinosaurs. This conclusion has been used to imply that Caudipteryx
may not have been correctly interpreted as a feathered non?avialan theropod,
but instead that this taxon represents some kind of flightless bird. We
review the evidence for this claim at the level of both the included fossil
specimen data, and in terms of the validity of the results presented. There
is no reason - phylogenetic, morphometric or otherwise - to conclude that
Caudipteryx is anything other than a small non-avialan theropod dinosaur.

Salgado, L., Coria, R.A., and Chiappe, L.M. 2005. Osteology of the sauropod
embryos from the Upper Cretaceous of Patagonia. Acta Palaeontologica
Polonica 50 (1): 79-92.

Exceptionally well?preserved embryonic skulls of Upper Cretaceous (Campanian
Anacleto Formation) sauropods from Auca Mahuevo (Neuquén Province,
Argentina) provide important insights into the ontogeny and evolution of
titanosaurian neosauropods. The most important cranial modifications
occurring during titanosaurian ontogeny appear to be centered on the
infraorbital and narial regions, which exhibit a substantial degree of
"mosaic" evolution. On one hand, the Auca Mahuevo embryos show a large jugal
that forms part of the lower margin of the skull and unretracted external
nares, as indicated by the position and orientation of the lacrimals as well
as the anterior extension of the frontals. Both of these features are
ancestral for neosauropods, being present in prosauropods. On the other
hand, the embryonic skull exhibits a large ventral notch, tentatively
interpreted as homologous to the neosauropod preantorbital fenestra, that
opens ventral to the jugal and between the maxilla and the quadratojugal,
and a temporal region that closely resembles the adult neosauropod
condition. This mosaic of character states indicates that different regions
of the skull of titanosaurian neosauropods acquired their characteristic
morphology at substantially different rates during their ontogenetic
development.

Schubert, B.W. and Ungar, P.S. 2005. Wear facets and enamel spalling in
tyrannosaurid dinosaurs. Acta Palaeontologica Polonica 50 (1): 93-99.

Numerous paleontologists have noted wear facets on tyrannosaurid lateral
teeth over the past century. While several workers have proposed
explanations for these features, there remains to this day no consensus
concerning their etiology. Here we report on an examination of wear surfaces
on these teeth from the Upper Cretaceous (mid-Campanian) Judith River Group
of southern Alberta, Canada. This study reveals two distinct types of wear
features on the labial and lingual sides of tyrannosaurid lateral teeth:
irregular "spalled" surfaces and wear facets. The irregular spalled surfaces
typically extend to the apex of the tooth, which evidently reflects flaking
of enamel resulting from forces produced during contact between tooth and
food. These surfaces are often rounded, presumably from antemortem wear
following spalling. Wear
striations on these surfaces are oriented heterogeneously. The wear facets,
in contrast, occur on only one side of the tooth and are typically
elliptical in outline and evince parallel wear striations. Similar patterns
of parallel wear striations in extant mammals reflect tooth-tooth contact.
We therefore propose that wear facets in tyrannosaurids were formed by
repeated tooth-tooth contact between the lingual side of maxillary teeth and
labial side of dentary teeth. It remains unclear whether this contact was
serendipitous or adaptive, though it appears to be unusual for reptiles, as
we have found no evidence for wear facets in extant varanids and
crocodilians.

Also, Burgess Shale chaetognaths in this issue...