MACNBR   00242
MUSEO ARGENTINO DE CIENCIAS NATURALES "BERNARDINO RIVADAVIA"
Unidad Ejecutora - UE
artículos
Título:
Dermal armour histology of aetosaurs; Archosauria: Pseudosuchia, from the Upper Triassic of Argentina and Brazil
Revista:
LETHAIA
Editorial:
WILEY-BLACKWELL PUBLISHING, INC
Referencias:
Año: 2010
ISSN:
0024-1164
Resumen:
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One of the most striking features documented in aetosaurs is the presence
of an extensive bony
armour composed of several osteoderms. Here, we analyze the bone
microstructure of these elements in some South American Aetosaurinae aetosaurs,
including Aetosauroides scagliai. In general terms, Aetosaurinae osteoderms are compact structures characterized
by the presence of three tissue types: a basal cortex of poorly vascularized
parallel-fibred bone tissue, a core of highly vascularised fibro-lamellar bone,
and an external cortex of rather avascular lamellar bone tissue. Sharpeys
fibres are more visible at the internal core, toward the lateral margins and
aligned parallel to the major axis of the dermal plate. No evidence of
metaplastic origin is reported in the osteoderms, and we hypothesize an
intramembraneous ossification for these elements. The bone tissue distribution
reveals that the development of the osteoderm in Aetosaurinae starts in a
position located medial to the plate midpoint, and the main sites of active
osteogenesis occur towards the lateral and medial edges of the plate. The osteoderm
ornamentation is originated and maintained by a process of resorption and
redeposition of the external cortex, which also includes preferential bone
deposition in some particular sites. Given that no secondary reconstruction
occurs in the osteoderms, growth marks are well preserved and they provide very
important information regarding the relative age and growth pattern of Aetosaurinae aetosaurs.