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Dino cartilage: it is important to consider
This just out:
Holliday CM, Ridgely RC, Sedlmayr JC, Witmer LM (2010) Cartilaginous Epiphyses
in Extant Archosaurs and Their Implications for
Reconstructing Limb Function in Dinosaurs. PLoS ONE 5(9): e13120.
Extinct archosaurs, including many non-avian dinosaurs, exhibit relatively
simply shaped condylar regions in their appendicular
bones, suggesting potentially large amounts of unpreserved epiphyseal
(articular) cartilage. This "lost anatomy" is often
underappreciated such that the ends of bones are typically considered to be the
joint surfaces, potentially having a major impact on
functional interpretation. Extant alligators and birds were used to establish
an objective basis for inferences about cartilaginous
articular structures in such extinct archosaur clades as non-avian dinosaurs.
Limb elements of alligators, ostriches, and other
birds were dissected, disarticulated, and defleshed. Lengths and condylar
shapes of elements with intact epiphyses were measured.
Limbs were subsequently completely skeletonized and the measurements repeated.
Removal of cartilaginous condylar regions resulted in
statistically significant changes in element length and condylar breadth.
Moreover, there was marked loss of those cartilaginous
structures responsible for joint architecture and congruence. Compared to
alligators, birds showed less dramatic, but still
significant changes. Condylar morphologies of dinosaur limb bones suggest that
most non-coelurosaurian clades possessed large
cartilaginous epiphyses that relied on the maintenance of vascular channels
that are otherwise eliminated early in ontogeny in
smaller-bodied tetrapods. A sensitivity analysis using cartilage correction
factors (CCFs) obtained from extant taxa indicates that
whereas the presence of cartilaginous epiphyses only moderately increases
estimates of dinosaur height and speed, it has important
implications for our ability to infer joint morphology, posture, and the
complicated functional movements in the limbs of many
extinct archosaurs. Evidence suggests that the sizes of sauropod epiphyseal
cartilages surpassed those of alligators, which account
for at least 10% of hindlimb length. These data suggest that large
cartilaginous epiphyses were widely distributed among non-avian
archosaurs and must be considered when making inferences about locomotor
functional morphology in fossil taxa.
It's PLoS: go read it yourself! :-)
Thomas R. Holtz, Jr.
Email: email@example.com Phone: 301-405-4084
Office: Centreville 1216
Senior Lecturer, Vertebrate Paleontology
Dept. of Geology, University of Maryland
Faculty Director, Science & Global Change Program, College Park Scholars
Mailing Address: Thomas R. Holtz, Jr.
Department of Geology
Building 237, Room 1117
University of Maryland
College Park, MD 20742 USA