CERDA Ignacio Alejandro
congresos y reuniones científicas
Comparative palaeohistology of Triassic rauisuchian and aetosaurian osteoderms (Archosauria: Pseudosuchia)
TORSTEN M. SCHEYER; JULIA B. DESOJO; IGNACIO A. CERDA
Congreso; 71th meeting of the Society of Vertebrate Paleontology; 2011
Osteoderm material of eight rauisuchian taxa (Batrachotomus kupferzellensis from Germany, Prestosuchus chiniquensis, P. loricatus and Rauisuchus tiradentes from Brazil, Ticinosuchus ferox and a possible juvenile rauisuchian from Switzerland, Tikisuchus romeri and the putative Yarasuchus deccanensis from India), ten aetosaurian taxa (incl. Aetosaurus ferratus and Paratypothorax andressorum from Germany, Stagonolepis olenkae from Poland, and Adamanasuchus eisenhardtae, Calyptosuchus wellesi, Desmatosuchus spp., Paratypothorax sp., Stagonolepididae, Tecovasuchus chatterjeei and Typothorax coccinarum from North America), and the Upper Triassic pseudosuchian Revueltosaurus callenderi from PetrifiedForest National Park, Arizona, as an outgroup were sampled histologically to elucidate the morphogenesis and structure of dermal armour in these diverse and widespread lineages of pseudosuchian archosaurs. Whereas the rauisuchian samples were found to be rather compact bones, usually lacking significant bone remodelling or large areas of cancellous bone, thus presenting good growth records, the aetosaurian samples showed well developed diploe structures in which the cancellous part can be quite extensive. This is in contrast topreviously sampled Aetosaurinae osteoderms from South America (including Aetosauroides scagliai), which generally lacked a larger area of interior cancellous bone. In the rauisuchians, highly vascularised woven- or fibrolamellar bone tissue deposited in the core areas indicates higher growth rates early in development, whereas a more compact parallel-fiberedbone matrix indicates reduced growth rates later in development. In the aetosaurian samples, woven- or fibrolamellar bone tissue, previously described also in Aetosaurinae osteoderms from South America, was found in T. coccinarum, whereas the other aetosaur osteoderms were predominantly composed of parallel-fibred or lamellar-zonal bone. In the R. callenderi osteoderm, the interior core consisted of dense cancellous bone, with dense trabecular bone being present only in the thick central region. Otherwise the specimen was composed of(often densely remodelled) parallel-fibred bone tissue.