2 refs

Abstract
The theory that birds evolved from a group of small terrestrial theropod dinosaurs has created much controversy.
One argument proposed against this theory is that the lungs of early theropods were incapable of sustaining
endothermic gas exchange requirements and could not have given rise to the lungs of birds. A reexamination of the
comparative physiological and morphological literature combined with a theoretical analysis of gas exchange
potential indicates that non-avian lungs would not constrain the gas exchange requirements of early endotherms.
Furthermore, our analysis suggests that factors besides diffusive gas exchange were important in the evolution of the
distinct morphology of the highly effective avian and mammalian lungs. © 1999 Elsevier Science B.V. All rights
reserved.
Keywords : Endothermy, dinosaurs; Evolution, dinosaurs to birds; Exercise, maximum O2 uptake, dinosaurs; Metabolism, dinosaurs;
Theropoda, dinosaurs

FEATURE ARTICLE
Allosaurus,Crocodiles, and Birds:
Evolutionary Clues From Spiral Computed
Tomography of an Endocast
SCOTT W. ROGERS*
Because the brain does not usually leave direct evidence of its existence in the fossil record, our view of this structure
in extinct species has relied upon inferences drawn from comparisons between parts of the skeleton that do fossilize
or with modern-day relatives that survived extinction. However, soft-tissue structure preservation may indeed
occasionally occur, particularly in the endocranial space. By applying modern imaging and analysis methods to such
natural cranial ''endocasts,'' we can now learn more than ever thought possible about the brains of extinct species. I
will discuss one such example in which spiral computed tomography (CT) scanning analysis has been successfully
applied to reveal preserved internal structures of a naturally occurring endocranial cast of Allosaurus fragilis, the
dominant carnivorous dinosaur of the late Jurassic period. The ability to directly examine the neuroanatomy of an
extinct dinosaur, whose modern-day relatives are birds and crocodiles, has exciting implications about Allosaurus'
behavior, its adaptive responses to its environment, and its eventual extinction. Anat Rec (New Anat) 257:162-173,
1999.r 1999 Wiley-Liss, Inc.
KEY WORDS: Allosaurus; brain; brain imaging; behavior; comparative anatomy; dinosaur; evolution; neuroanatomy; spiral
computed tomography
THE ANATOMICAL RECORD (NEW ANAT.) 257:162-173, 1999