Tithonian Marine Herpetofaunas from the Neuquen Basin (Northwest Patagonia, Argentina)

FERNÁNDEZ, M. ; GASPARINI, Z.; HERRERA, Y.

Beijing, China

Simposio; International Symposium on Triassic and later Marine Vertebrate Faunas; 2010

Marine reptiles from the Neuquén Basin represent the best record of Jurassic marine reptiles from Gondwana. The Neuquén Basin is located on the eastern side of the Andes in Argentina and central Chile, between 32º and 40ºS latitude. Of particular interest are Tithonian (Late Jurassic) marine reptiles that have been found in transgressive offshore facies of the Vaca Muerta Formation. This Tithonian record is outstanding for two main reasons: first, it documents a complete succession of early, middle, and late Tithonian-Berrasian marine reptile faunas dominated by off-shore predators; second, in at least four localities, natural casts of internal cavities of metriorhynchid skulls have been found. Tithonian marine assemblages of the Neuquén Basin include ichthyosaurs (Caypullisaurus bonapartei, Aegirosaurus sp. and another ophthalmosaurid); marine testudinata (Neusticemys neuquina and Notoemys laticentralis); pliosaurids (Pliosaurus sp.),and metriorhynchids (Cricosaurus araucanensis and Dakosaurus andiniensis). Although metriorhynchids in the Neuquén Basin are represented only by two nominated taxa, C. araucanensis and D. andiniensis, they represent both extremes of the morphological diversity of the clade. Another peculiarity of metriorhynchid records is that skull materials are three-dimensioned preserved contrasting with most flattened metriorhynchids recovered from European basins. On the other hand, natural casts of C. araucanensis from the Vaca Muerta Fm. provide exceptional information allowing the reconstruction of soft organs housed in the snout of these metriorhynchids. Soft organs reconstructed include exocrine glands (salt glands), and the paranasal sinus system. Recent finding of a natural cast of D. andiniensis snout, including salt gland casts, is reported