Allosaurus hatchling from Portugal

["bh480@scn.org" <bh480@scn.org>]

From: Ben Creisler bh480@scn.org
My email has been fried for the past few days. In case this article has not
been mentioned here yet:
Proceedings: Biological Sciences 
FirstCite Early Online Publishing

Oliver W. M. Rauhut and Regina Fechner
Early development of the facial region in a non-avian theropod dinosaur

Abstract: 
An isolated maxilla of the theropod dinosaur Allosaurus from the Late
Jurassic (the Kimmeridgian, 153 million years ago) of Portugal is the first
cranial remain of a non-coelurosaurian theropod hatchling reported so far,
and sheds new light on the early cranial development of non-avian
theropods. Allosaurus hatchlings seem to have been one-seventh or less of
the adult length and are thus comparable in relative size to hatchlings of
large extant crocodile species, but are unlike the relatively larger
hatchlings in coelurosaurs. The snout experienced considerable positive
allometry and an increase in tooth count during early development. The
element is especially noteworthy for the abundant and well-developed
features associated with the paranasal pneumatic system. Pneumatic
structures present include all those found in adult allosaurids and most
are even more developed than in adult skulls. Together with evidence on the
ontogeny of the tympanic pneumatic system in allosaurids, these findings
demonstrate that cranial pneumaticity developed early in theropod ontogeny.
The strong development of pneumatic features in early ontogenetic stages of
non-avian theropods supports the hypothesis that pneumatization of cranial
bones was opportunistic and indicates that heterochrony played an important
role in the evolution of craniofacial pneumaticity in this group. 



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