Bone shell microstructure of Condorchelys antiqua Sterli,2008, a stem turtle from the Jurassic of Patagonia

IGNACIO A. CERDA; JULIANA STERLI; TORSTEN M. SCHEYER

COMPTES RENDUS PALEVOL

ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER

Lugar: Paris; Año: 2016 vol. 15 p. 133 - 146

1631-0683

tThe histology of the turtle shell has proven to be a valuable source of characters for thestudy of development and shell origin, as well as early turtles? lifestyles and systematics.Here we describe and discuss the shell bone microanatomy and histology of Condorchelysantiqua, a stem turtle from the Lower Jurassic of Patagonia. Examination of several elements(including costals, neurals, peripherals and plastral plates) reveals that the shell bones con-sist of a diploe structure in which the interior area of cancellous bone is framed by externaland internal cortices. Whereas the external cortex is mostly composed of structural fiberbundles, histological composition of the internal cortex is more variable, exhibiting struc-tural fiber bundles and/or parallel fibered bone. This histological variation in the internalcortex allows discerning between different types of plates. The cancellous bone is mostlywell developed and consists of fine trabeculae composed of secondary lamellar bone tissue.Predominance of structural fiber bundles in the shell bones suggests that metaplasia playsan important role during the development of the shell in this taxon. Comparison with otherstem Testudines (including Proganochelys quenstedti, Proterochersis robusta, Kayentachelyssp., Eileanchelys waldmani, and Heckerochelys romani) reveals that the shell histology ofC. antiqua resembles more H. romani and E. waldmani than the other stem taxa. The obtainedvalues of compactness of C. antiqua shell bones suggest an aquatic lifestyle for this taxon.