Paleohistology of Susisuchus anatoceps (Crocodylomorpha, Neosuchia): Comments on Growth Strategies and Lifestyle.

Autor: Juliana M Sayão, Renan A M Bantim, Rafael C L P Andrade, Flaviana J Lima, Antônio A F Saraiva, Rodrigo G Figueiredo, Alexander W A Kellner
Jazyk: angličtina
Rok vydání: 2016
Předmět:
Zdroj: PLoS ONE, Vol 11, Iss 5, p e0155297 (2016)
Druh dokumentu: article
ISSN: 1932-6203
DOI: 10.1371/journal.pone.0155297
Popis: Susisuchus anatoceps is a neosuchian crocodylomorph lying outside the clade Eusuchia, and associated with the transition between basal and advanced neosuchians and the rise of early eusuchians. The specimen MPSC R1136 comprises a partially articulated postcranial skeleton and is only the third fossil assigned to this relevant taxon. Thin sections of a right rib and right ulna of this specimen have been cut for histological studies and provide the first paleohistological information of an advanced non-eusuchian neosuchian from South America. The cross-section of the ulna shows a thick cortex with 17 lines of arrested growth (LAGs), a few scattered vascular canals, and primary and secondary osteons. This bone has a free medullary cavity and a spongiosa is completely absent. Thin sections of the rib show that remodeling process was active when the animal died, with a thin cortex and a well-developed spongiosa. In the latter, few secondary osteons and 4 LAGs were identified. According to the observed data, Susisuchus anatoceps had a slow-growing histological microstructure pattern, which is common in crocodylomorphs. The high number of ulnar LAGs and the active remodeling process are indicative that this animal was at least a late subadult, at or past the age of sexual maturity. This contradicts previous studies that interpreted this and other Susisuchus anatoceps specimens as juveniles, and suggests that full-grown adults of this species were relatively small-bodied, comparable in size to modern dwarf crocodiles.
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