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Sauropodomorph postcranial skeletal pneumaticity evolution

From: Ben Creisler

New advance online paper in Acta Palaeontologica Polonica:

Adam M. Yates, Mathew J. Wedel, and Matthew F. Bonnan (2011)
The early evolution of postcranial skeletal pneumaticity in sauropodomorph
Acta Palaeontologica Polonica in press
available online 07 Mar 2011 doi:10.4202/app.2010.0075

Postcranial skeletal pneumaticity (PSP) is present in a range of basal
sauropodomorphs spanning the basal sauropodomorph?sauropod transition. We
describe the PSP of five taxa, Plateosaurus engelhardti, Eucnemesaurus
fortis, Aardonyx celestae, Antetonitrus ingenipes and an unnamed basal
sauropod from Spion Kop, South Africa (hereafter referred to as the Spion
Kop sauropod). The PSP of Plateosaurus is apparently sporadic in its
occurrence and has only been observed in very few specimens, in which it is
of very limited extent, affecting only the posterior cervical vertebrae and
possibly the mid dorsals in one specimen. The PSP of Eucnemesaurus,
Aardonyx, Antetonitrus and the Spion Kop sauropod consists of subfossae
(fossa-within-fossa structures) that excavate the vertices of the posterior
infradiapophyseal fossae of the posterior dorsal vertebrae. These subfossae
range from simple shallow depressions (Eucnemesaurus) to deep, steep-sided,
internally subdivided and asymmetrically developed chambers (Antetonitrus).
The middle and anterior dorsal vertebrae of these taxa lack PSP,
demonstrating that abdominal air sacs were the source of the invasive
diverticula. The presence of pneumatic features within the
infradiapophyseal fossae suggest that the homologous fossae of more basal
saurischians and dinosauriforms were receptacles that housed pneumatic
diverticula. We suggest that it is probable that rigid non-compliant lungs
ventilated by compliant posterior air sacs evolved prior to the origination
of Dinosauria. 

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