Phylogenetic relationships ofNecrosuchus ionensisSimpson, 1937 and the early history of caimanines

Abstract

Cranial fragments associated with the holotype of Necrosuchus ionensis reveal a dorsally shifted foramen aereum on the quadrate and a long, slender descending process of the exoccipital lateral to the basioccipital and approaching the basioccipital tubera. The former suggests that Necrosuchus is an alligatoroid and not a crocodylid, as first suggested; and the latter that it is a caiman. The scapulocoracoid shows evidence of early closure of the synchondrosis, further supporting a caiman affinity. Although we cannot yet pinpoint the phylogenetic placement of Necrosuchus amongst caimans, it nevertheless establishes a caimanine presence in South America by the Early Palaeocene. A review of other Palaeocene–Eocene caimans reveals a complex biogeographical history suggesting multiple dispersal events between North and South America, even if the modern caiman assemblage is monophyletic. © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 163, S228–S256.

Reptiles Extintos - Volumen en Homenaje a Zulma Gasparini

“…Argentinean fossil alligatorids are in general fragmentary and belong to the clade Caimaninae (Brochu, 1999(Brochu, , 2011Bona, 2007) which together with Alligatorinae constitutes one of the two clades of Alligatoridae.…”

“…The re-interpretation of N. ionensis as a basal caiman has biogeographical implications, establishing the presence of caimanines in southern South America early in the Cenozoic and extending back the early history of caimans (Brochu, 2011).…”

“…Based on fragmentary and disassociated material, Bravard (1858) (1912), who figured the type material. Available morphological information used to reconstruct phylogenetic relationships is insufficient to propose the phylogenetic position of this species within alligatorids (Brochu, 1999(Brochu, , 2010(Brochu, , 2011Bona et al, 2013a,b). Nevertheless, Caiman australis is one of at least five valid Caiman species recorded in the Late…”

“…Eocaiman was erected by Recently, a new small species, E. itaboraiensis Pinheiro et al, 2013, was described on the basis of an anterior fragment of a left mandibular rami and one isolated tooth from the middle-upper Paleocene Itaboraí Basin (Rio de Janeiro State, Brazil; Pinheiro et al, 2013). Eocaiman is a basal Caimaninae (Brochu, 1999(Brochu, , 2011Bona, 2007) with a low mandible at the symphyseal region and a long symphysis (extended back to the 5th alveolus). This genus is distributed from the Paleogene of Patagonia to the Middle Miocene of Colombia (Langston, 1965).…”

New crocodylian remains from the Solimões Formation (lower Eocene–Pliocene), State of Acre, Southwestern Brazilian Amazonia

“…Furthermore, postcranial elements have recieved much less priority in descriptions because they are usually considered to have less systematic information, as suggested by the minor presence of postcranial characters in phylogenetic analyses (e.g. Brochu, 1997Brochu, , 2011Brochu, , 2013.…”