INVESTIGADORES
CERDA Ignacio Alejandro
congresos y reuniones científicas
Título:
Osteoderm microstructure of the rauisuchian archosaurs from the Santa Maria Formation (Middle ?Late Triassic) of Brazil
Autor/es:
IGNACIO A. CERDA; JULIA B. DESOJO; TORSTEN M. SCHEYER; CESAR M. SCHULTZ
Lugar:
San Juan
Reunión:
Congreso; IV Congreso Latinoamericano de Paleontología de; 2011
Resumen:
In this contribution we analyse and discuss the microanatomy and histology of postcranial osteoderms of ?rauisuchians? from the Santa Maria Formation (Middle?Late Triassic) of Brazil. The studied sample includes osteoderms of Prestosuchus chiniquensis Huene 1938 UFRGSPV0156T and UFRGS-PV0629T) and two undetermined ?rauisuchians? (UFRGSPV0152T and CPEZ-239). Whereas the osteoderms of UFRGS-PV0156T and CPEZ-239 have a rather compact structure, specimens UFRGS-PV0629T and UFRGSPV0152T show a diploe architecture, with a central cancellous core bordered by two compact cortices. Both external and basal cortices are composed of poorly vascularised, coarse parallel-fibred bone and networks of overcrossing mineralized fibre bundles. The internal region of the non-remodelled specimens consists of a well vascularized core in which the intrinsic fibres exhibit important variation (even in the same specimen), ranging from coarse, parallel fibred to woven fibred bone tissues. Growth marks are well recorded in both basal and external cortices. Differences in the bone microstructure (compact vs. diploe) appear to be related to the ontogenetic stage of specimens (osteoderms of the older specimens are more remodelled). Hence, age estimation based on the count of growth marks in ?rauisuchians? osteoderms is only reliable in the first stages of the ontogeny. The bone microstructure suggests that ?rauisuchian? osteoderms were originated through a mechanism that involves both intramemenbraneuos and metaplastic ossifications (Scheyer and Desojo, in press).Prestosuchus chiniquensis Huene 1938 UFRGSPV0156T and UFRGS-PV0629T) and two undetermined ?rauisuchians? (UFRGSPV0152T and CPEZ-239). Whereas the osteoderms of UFRGS-PV0156T and CPEZ-239 have a rather compact structure, specimens UFRGS-PV0629T and UFRGSPV0152T show a diploe architecture, with a central cancellous core bordered by two compact cortices. Both external and basal cortices are composed of poorly vascularised, coarse parallel-fibred bone and networks of overcrossing mineralized fibre bundles. The internal region of the non-remodelled specimens consists of a well vascularized core in which the intrinsic fibres exhibit important variation (even in the same specimen), ranging from coarse, parallel fibred to woven fibred bone tissues. Growth marks are well recorded in both basal and external cortices. Differences in the bone microstructure (compact vs. diploe) appear to be related to the ontogenetic stage of specimens (osteoderms of the older specimens are more remodelled). Hence, age estimation based on the count of growth marks in ?rauisuchians? osteoderms is only reliable in the first stages of the ontogeny. The bone microstructure suggests that ?rauisuchian? osteoderms were originated through a mechanism that involves both intramemenbraneuos and metaplastic ossifications (Scheyer and Desojo, in press).