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Rauisuchian osteoderm microstructure

From: Ben Creisler

A new online paper:

Ignacio Alejandro Cerda, Julia Brenda Desojo, Torsten M. Scheyer &
Cesar Leandro Schultz (2013)
Osteoderm microstructure of “rauisuchian” archosaurs from South America.
Geobios (advance online publication)
doi: http://dx.doi.org/10.1016/j.geobios.2013.01.004

In this contribution we analyze and discuss the microanatomy and
histology of postcranial osteoderms of a number of “rauisuchians” from
different localities of South America (Argentina and Brazil). The
studied sample includes osteoderms of Fasolasuchus tenax, Prestosuchus
chiniquensis, Saurosuchus galilei and an undetermined rauisuchian from
Brazil. The bone microanatomy of the osteoderms is variable: whereas
some specimens have a rather compact structure, others show a diploe
architecture with a central cancellous core bordered by two compact
cortices. Both external and basal cortices are mainly composed of
poorly vascularized, fine and coarse parallel fibred bone and networks
of interwoven and mineralized fiber bundles. The internal region of
the non-remodeled specimens consists of a well-vascularized core in
which the intrinsic fibers exhibit important variations (even in the
same specimen), ranging from coarse, parallel-fibred to woven-fibred
bone tissues. Lines of arrested growth (LAGs) are well recorded in
both basal and external cortices. Differences in the bone
microstructure (compact vs. diploe) could be related to the age, sex
and reproductive status of the sampled individuals. Hence, age
estimation based on the count of LAGs in rauisuchian osteoderms
appears to be reliable only in the early stages of ontogeny. The bone
microstructure suggests that rauisuchian osteoderms were originated
through a mechanism that involves both intramembranous and metaplastic