Europatitan eastwoodi, a new sauropod from the lower Cretaceous of Iberia in the initial radiation of somphospondylans in Laurasia.

Fidel Torcida Fernández-Baldor,Pedro Huerta,José Ignacio Canudo,Miguel Moreno-Azanza,Diego Montero

doi:10.7717/peerj.3409

Fidel Torcida Fernández-Baldor, Pedro Huerta + Show 3 more

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https://doi.org/10.7717/peerj.3409

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Abstract

The sauropod of El Oterillo II is a specimen that was excavated from the Castrillo de la Reina Formation (Burgos, Spain), late Barremian–early Aptian, in the 2000s but initially remained undescribed. A tooth and elements of the axial skeleton, and the scapular and pelvic girdle, represent it. It is one of the most complete titanosauriform sauropods from the Early Cretaceous of Europe and presents an opportunity to deepen our understanding of the radiation of this clade in the Early Cretaceous and study the paleobiogeographical relationships of Iberia with Gondwana and with other parts of Laurasia. The late Barremian–early Aptian is the time interval in the Cretaceous with the greatest diversity of sauropod taxa described in Iberia: two titanosauriforms, Tastavinsaurus and Europatitan; and a rebbachisaurid, Demandasaurus. The new sauropod Europatitan eastwoodi n. gen. n. sp. presents a series of autapomorphic characters in the presacral vertebrae and scapula that distinguish it from the other sauropods of the Early Cretaceous of Iberia. Our phylogenetic study locates Europatitan as the basalmost member of the Somphospondyli, clearly differentiated from other clades such as Brachiosauridae and Titanosauria, and distantly related to the contemporaneous Tastavinsaurus. Europatitan could be a representative of a Eurogondwanan fauna like Demandasaurus, the other sauropod described from the Castrillo de la Reina Formation. The presence of a sauropod fauna with marked Gondwananan affinities in the Aptian of Iberia reinforces the idea of faunal exchanges between this continental masses during the Early Cretaceous. Further specimens and more detailed analysis are needed to elucidate if this Aptian fauna is caused by the presence of previously unnoticed Aptian land bridges, or it represents a relict fauna from an earlier dispersal event.

Highlights

The vertebrate faunas of the Early Cretaceous of the Iberian Peninsula are of particular interest on account of the special paleobiogeographical location of the Iberian microplate
Bearing this fact in mind, modern paleobiogeographical models point out that Europe and “Gondwanan” territories possessed a common Eurogondwanan fauna during the earliest Cretaceous, but that from the Barremian onwards dispersal took place independently in Gondwana and Laurasia, with the isolation of the European faunas (Ezcurra & Agnolın, 2012). To resolve this paleobiogeographical problem, new dinosaur material needs to be put in its correct phylogenetic position and its age established. This may be the only way of ascertaining whether the paleobiogeographical complexity of the Iberian Peninsula in the Early Cretaceous was the result of processes of dinosaur dispersal only at certain points in time or came about as a continuous process
The aim of the present paper is to provide a complete description of the sauropod of El Oterillo II, to ascertain its phylogenetic position in relation to the most recent proposals for Titanosauriformes, and to draw relevant paleobiogeographical conclusions

Summary

Introduction

The vertebrate faunas of the Early Cretaceous of the Iberian Peninsula are of particular interest on account of the special paleobiogeographical location of the Iberian microplate. The Apulian route could have facilitated these migratory movements intermittently until the Eocene (Gheerbrant & Rage, 2006; Canudo et al, 2009) Bearing this fact in mind, modern paleobiogeographical models point out that Europe and “Gondwanan” territories possessed a common Eurogondwanan fauna during the earliest Cretaceous, but that from the Barremian onwards dispersal took place independently in Gondwana and Laurasia, with the isolation of the European faunas (Ezcurra & Agnolın, 2012). To resolve this paleobiogeographical problem, new dinosaur material needs to be put in its correct phylogenetic position and its age established. A interesting group for studying this question is the sauropod dinosaurs due to their broad distribution on a worldwide scale in the Cretaceous

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