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

Abstract

Please cite this article in press as:Cerda, I.A., et al., Bone shell microstructure of Condorchelys antiqua Sterli, 2008, a stem turtle from the Jurassic of Patagonia. C. R. Palevol (2015), http://dx. a b s t r a c tThe histology of the turtle shell has proven to be a valuable source of characters for the study 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 Condorchelys antiqua, 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 consist of a diploe structure in which the interior area of cancellous bone is framed by external and internal cortices. Whereas the external cortex is mostly composed of structural fiber bundles, histological composition of the internal cortex is more variable, exhibiting structural fiber bundles and/or parallel fibered bone. This histological variation in the internal cortex allows discerning between different types of plates. The cancellous bone is mostly well developed and consists of fine trabeculae composed of secondary lamellar bone tissue. Predominance of structural fiber bundles in the shell bones suggests that metaplasia plays an important role during the development of the shell in this taxon. Comparison with other stem Testudines (including Proganochelys quenstedti, Proterochersis robusta, Kayentachelys sp., Eileanchelys waldmani, and Heckerochelys romani) reveals that the shell histology of C. antiqua resembles more H. romani and E. waldmani than the other stem taxa. The obtained values of compactness of C. antiqua shell bones suggest an aquatic lifestyle for this taxon.

New remains of the aquatic turtle Hydromedusa casamayorensis (Pleurodira, Chelidae) from the middle Eocene of Patagonia: taxonomic validation and phylogenetic relationships

“…; Cerda et al . ), the shell histology of Hydromedusa casamayorensis retains plesiomorphic characters such as the diploe structure of the shell, presence of Sharpey's fibres in the external cortex, parallel‐fibred bone in the internal cortex, and metaplastic incorporation of dermal interwoven structural fibre. Hydromedusa casamayorensis shares with other chelids the reduction in thickness of the ICO, an external cortex with ISF of similar length and thickness, and primary canals that frequently anastomose forming a reticular pattern (Scheyer ).…”

Comparative data on the differentiation and growth of bone ornamentation in gnathostomes (Chordata: Vertebrata)

“…Detailed histological studies of ornamented carapaces in various extant and extinct turtle taxa (e.g., stem‐turtles, Trionychidae, Pelomedusidae, Podocnemidae, etc.) were recently conducted by Scheyer and Sánchez‐Villagra (), Scheyer et al (), and Cerda et al (). The occurrence of local remodeling, in the form of resorption and reconstruction topographically related to ornamentation, was mentioned and clearly illustrated in the trionychid Aspideretoides (Scheyer et al, ), the podocnemyd Podocnemys erythrocephala , the bothremydid (an extinct taxon) Bothremys barbieri (Scheyer et al, ), and the Jurassic stem turtle Condorchelys antiqua (Cerda et al, ).…”

“…were recently conducted by Scheyer and Sánchez‐Villagra (), Scheyer et al (), and Cerda et al (). The occurrence of local remodeling, in the form of resorption and reconstruction topographically related to ornamentation, was mentioned and clearly illustrated in the trionychid Aspideretoides (Scheyer et al, ), the podocnemyd Podocnemys erythrocephala , the bothremydid (an extinct taxon) Bothremys barbieri (Scheyer et al, ), and the Jurassic stem turtle Condorchelys antiqua (Cerda et al, ). However, an interpretation referring to pathological disorders was given to that observation: superficial carapace remodeling would reflect “a reaction to incipient osteomyelitis or shell rot ” (Scheyer and Sanchez‐Villagra, 2007).…”

Comparative analysis of the shape and size of the middle ear cavity of turtles reveals no correlation with habitat ecology

“…; Cerda et al. ). Although the ecologies of A. africanus and K. aprix , which provide evidence for the earliest changes in turtle ear morphology, are unknown, the available data for C. antiqua and E. waldmani suggest that the turtle middle ear could have evolved during an aquatic stage of stem‐turtle evolution.…”