A new specimen of Platypterygius sachicarum (Reptilia, Ichthyosauria) from the Early Cretaceous of Colombia and its phylogenetic implications

ABSTRACT

Platypterygius sachicarum is one of the few Lower Cretaceous ichthyosaurian species described from the Hauterivian–Aptian-aged Paja Formation, the most complete Lower Cretaceous sedimentary sequence in northern South America. To date, P. sachicarum has been described only from a single skull, limiting morphological, stratigraphic, and phylogenetic comparisons. Here, we describe a new skull and associated postcranium of upper Barremian age from Villa de Leyva, Colombia, which represent the first documented postcranial remains of this species and enable detailed comparison with other Early Cretaceous ophthalmosaurid ichthyosaurs. Platypterygius sachicarum shares many morphological similarities with contemporaneous taxa from Europe but differs in both skull and tooth morphology from coeval South American species from northern South America and from the eastern Pacific. The additional data provide new diagnostic characters for this species and resolve the position of P. sachicarum as part of a polytomy of other species historically referred to Platypterygius. However, as with previous analyses, all recovered clades are poorly supported. The rich vertebrate fossil record of the Paja Formation provides an unparalleled opportunity to explore paleobiogeographic and paleoecological questions pertaining to Cretaceous marine reptiles; however, in most cases, a robust stratigraphic and phylogenetic framework remains elusive.

ACKNOWLEDGMENTS

We thank G. Amador and C. Amador, who found the specimen and brought it to the attention of the CIP; F. H. Parra, J. De Dios Parra, and C. Parra (CIP), who prepared the specimen; S. Padilla (CIP), who helped establish the collaboration with E.E.M.; the Alcaldía Municipal de Villa de Leyva and C. Igua Robles (alcalde), who provided funds for excavation; C. Jaramillo (STRI), the Smithsonian Tropical Research Institute, the Anders Foundation, 1923 Fund, G. D. and J. W. Johnson, and NSERC CREATE 466283-2015, who helped fund D.Y.C.; and a DFG Kooperationsanbahnung and MWK Anschubfinanzierung to E.E.M., which helped finance study of the specimen. B. Moon and M. Fernández provided constructive reviews that improved the manuscript.

ORCID

Dirley Cortés http://orcid.org/0000-0001-9409-7429

Erin E. Maxwell http://orcid.org/0000-0002-6032-6251