Aristonectes quiriquinensis sp. nov., a new highly derived elasmosaurid from the late Maastrichtian of central Chile

OTERO, R.A.; SOTO-ACUÑA, S.; O'KEEFE, F.R.; JOSE.P. O'GORMAN; STINNESBECK, W; SUÁREZ, M.A; RUBILAR-ROGERS, D; QUINZIO-SINN, L.A; SALAZAR, C

JOURNAL OF VERTEBRATE PALEONTOLOGY

SOC VERTEBRATE PALEONTOLOGY

Lugar: Lawrence; Año: 2014 vol. 34 p. 100 - 135

0272-4634

Here we describe a new species of elasmosaurid plesiosaur, named Aristonectes quiriquinensis, based on a partial skeleton recovered from late Maastrichtian beds of the Quiriquina Formation collected at Cocholgue (holotype) and a second juvenile specimen from the Quiriquina Island (paratype), both in central Chile. Prior to this research Aristonectes was considered to be monospecific and only included the enigmatic Aristonectes parvidens, the holotype of which consists of an incomplete skull and incomplete postcranium. Other material referred to the genus includes an incomplete juvenile skull and other postcranial materials from the late Maastrichtian of Antarctica, as well as a skull portion from the Quiriquina Formation of central Chile. The relationships of Aristonectes have been discussed controversially, with competing theories assigning the genus to Cryptoclididae, Elasmosauridae and Aristonectidae; however, there is a developing consensus that Aristonectes is a derived elasmosaurid. Comparing the studied specimen (holotype of A. quiriquinensis) with the holotype of A. parvidens, some characteristics may be explained by differences in their respective ontogenetic stages, whereas others are true autapomorphies. The elements preserved allow the first confident size estimates for adult Aristonectes, proving it to be a large plesiosaurian with a relatively large skull having abundant homodont teeth, moderately long and laterally compressed neck and relatively narrow trunk, with slender and elongate forelimbs narrower than the hindlimbs. The two specimens (holotype and paratype) are restricted to the late Maastrichtian of central Chile, posing questions concerning the austral circumpolar distribution of different elasmosaurids towards the end of the Cretaceous.