title: Paleohistology of Susisuchus anatoceps (Crocodylomorpha, Neosuchia): Comments on Growth Strategies and Lifestyle.
abstract: 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.
authors.affiliation: Laboratório de Biodiversidade do Nordeste, Centro Acadêmico de Vitória, Universidade Federal de Pernambuco.Vitória de Santo Antão, Pernambuco, Brazil.
authors.forename: Juliana M
authors.initials: JM
authors.lastname: Sayão
authors.affiliation: Laboratório de Biodiversidade do Nordeste, Centro Acadêmico de Vitória, Universidade Federal de Pernambuco.Vitória de Santo Antão, Pernambuco, Brazil.
authors.forename: Renan A M
authors.initials: RA
authors.lastname: Bantim
authors.affiliation: Laboratório de Biodiversidade do Nordeste, Centro Acadêmico de Vitória, Universidade Federal de Pernambuco.Vitória de Santo Antão, Pernambuco, Brazil.
authors.forename: Rafael C L P
authors.initials: RC
authors.lastname: Andrade
authors.affiliation: Laboratório de Biodiversidade do Nordeste, Centro Acadêmico de Vitória, Universidade Federal de Pernambuco.Vitória de Santo Antão, Pernambuco, Brazil.
authors.forename: Flaviana J
authors.initials: FJ
authors.lastname: Lima
authors.affiliation: Laboratório de Paleontologia, Universidade Regional do Cariri.Crato, Ceará, Brazil.
authors.forename: Antônio A F
authors.initials: AA
authors.lastname: Saraiva
authors.affiliation: Departamento de Ciências Biológicas, Universidade Federal do Espírito Santo. Vitória, Espírito Santo, Brazil.
authors.forename: Rodrigo G
authors.initials: RG
authors.lastname: Figueiredo
authors.affiliation: Laboratório de Sistemática e Tafonomia de Vertebrados Fósseis, Museu Nacional, Universidade Federal do Rio de Janeiro.Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: Alexander W A
authors.initials: AW
authors.lastname: Kellner
mesh_terms: D000489:Alligators and Crocodiles / Q000254:growth & development* / Q000502:physiology*; D000818:Animals; D005075:Biological Evolution; D001686:Biological Phenomena; D004777:Environment; D005580:Fossils; D008019:Life Style; D010829:Physiological Phenomena / Q000502:physiology; D012886:Skull / Q000254:growth & development / Q000502:physiology; D013020:South America