OPHTHALMOSAURIDS (ICHTHYOSAURIA: THUNNOSAURIA): ALPHA TAXONOMY, CLADES AND NAMES

FERNÁNDEZ, M.; CAMPOS, L.

Publicacion Electronica Asociacion Pleontologica Argentina

Asociacion Paleontologica Argentina

Año: 2015 p. 20 - 30

Thunnosaurian ichthyosaurs represent the paradigm of reptilian body designed for a pelagic life style. Most derived thunnosaurian,the ophthalmosaurids, have been traditionally considered as members of a declining lineage. New findings and the re-examination of historicalcollections radically changed our conceptions about them. Opthalmosaurids were ecologically more diverse than previously thought. The pastfew decades have seen an increase of nominal species spurred by new findings and analyses. A still unresolved problem is that many speciesare only known by their holotypes. Nevertheless, morphological disparity is a compelling argument for considering them as valid. All recentcladistic analyses of ichthyosaurs recover ophthalmosaurids as a clade. Neither the addition of new information nor the addition of newentities resulted in its collapse. On this basis, the assignment of Linnaean rank to this clade (Ophtalmosauridae) is reasonable as it satisfiedthe primary recommended criteria for taxa naming: monophyly and stability. As the lists of species and genus names are used as input in majordata bases for interpreting major turnover and/or extinction patterns, efforts must be focused on clarifying as much as possible the alphataxonomy. Two major pending issues are the delimitation of Ophthalmosaurus-Baptanodon, and Platypterygius. The case of Platypterygius iscomplex because the type species is poorly known, its holotype is lost, and there is no consensus among specialist about the species thatshould be included in this genus. On the other hand, we advocate for the use of the name Baptanodon natans instead of Ophthalmosaurus natans