New materials of the diplodocid sauropod Leinkupal laticauda from the Bajada Colorada Formation (Berriasian-Valanginian), Neuquén Province, Argentina

GALLINA, PABLO ARIEL; CANALE, JUAN IGNACIO; APESTEGUÍA, SEBASTIÁN

San Luis

Jornada; Reunión de Comunicaciones de la Asociación Paleontológica Argentina; 2017

The last diplodocid sauropods inhabited Patagonia in the Early Cretaceous. This was evidenced in 2014 by the finding of the first record of Diplodocidae for South America. The few recovered axial remains permitted the recognition of the new species Leinkupal laticauda Gallina, Apesteguía, Haluza, and Canale 2014. Successive fieldworks on the main quarry resulted in the discovery of additional material from the cranium and both the axial and appendicular skeleton. These include a partial preserved basicranium (MMCh-Pv232), an axis (MMCh-Pv158), an anterior cervical neural arch (MMCh-Pv173), an incomplete posterior cervical vertebra (MMCh-Pv161), one anterior (MMCh-Pv159) and three mid-caudal vertebrae (MMCh-Pv137/214/165), plus a right coracoid (MMCh-Pv114). Several characters show clear diplodocid affinities such as box-like basal tubera; distal end of paroccipital process rounded; neural spine of the axis situated entirely anterior to the postzygapophyseal facets; well-defined diapophyseal laminae and fossae in anterior caudal vertebrae; large pneumatic foraminae and ventral longitudinal hollows in anterior to mid-caudal centra; and a sub-rectangular coracoid outline. Besides, the presence of autapomorphic traits such as well-developed transverse process lateroventrally projected and very robust centroprezygapophyseal laminae in anterior caudal vertebrae allows referral to Leinkupal. A phylogenetic analysis recovers Leinkupal well-nested within Diplodocinae, but strikingly more closely related to derived laurasian diplodocines instead of basal Gondwanan forms as originally thought. This result permits to hypothesize a late colonization of South America by this clade around Jurassic-Cretaceous boundary. The new evidence also augments the knowledge on the anatomy of this diplodocid taxon and, at the same time, improves its diagnosis.