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POL Diego

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Título:

Revision of the holotype of Patagosaurus fariasi, a basal eusauropod from Patagonia

Autor/es:

HOLWERDA, F.; RAUHUT, O.W.; POL, D.

Lugar:

Mendoza

Reunión:

Congreso; 4th International Paleontological Congress; 2014

Resumen:

Patagosaurus fariasi is an early Middle Jurassic sauropod from the Cañadon Asfalto Fm., Patagonia, Argentina. Since its first description, it has been used in numerous phylogenetic analyses of sauropod dinosaurs. However, our current understanding of Patagosaurus is based on elements of several specimens, collected from two localities. Furthermore, at least one specimen of one of these localities is probably a different taxon. Therefore, a revision has been started of all Patagosaurus material, starting with the holotype PVL 4170, which is described and compared to other sauropods. The specimen has seven preserved cervical vertebrae, ten dorsals, the complete sacrum consisting of five sacral vertebrae, and caudals. Furthermore, the right ilium, pubis and the distal fused parts of the ischia, and the right femur are preserved. The cervicals are opisthocoelous, and neurocentral sutures are present, indicating that the animal was still growing. There is a prominent ventral keel, with two lateral fossae, as in Amygdalodon, Lapparentosaurus and Spinophorosaurus, but in contrast to Cetiosaurus and derived sauropods. Laterally, a shallow pleurocoel is present which is deeper cranially, as in Spinophorosaurus and Lapparentosaurus, and not as in Cetiosaurus and Tazoudasaurus. Cranially, the intraprezygapophyseal laminae do not meet, as in Tazoudasaurus and Cetiosaurus. The anterior and mid-dorsals are mildly opisthocoelous as in Chebsaurus. The dorsal neural spines are higher than the centrum, and have high neural arches with a wider distal dorsal end of the neural spine as in Amygdalodon. A ventral keel is present in anterior and mid-dorsals but not in posterior dorsals. Laterally only a small shallow fossa is present, as in Cetiosaurus and Lapparentosaurus. An infradiapophyseal fenestra below the transverse processes is present, as in Barapasaurus and possibly Tazoudasaurus. The caudals are amphicoelus, as in most basal sauropods. The ilium is highly arched and craniocaudally elongated. The pubis is twisted towards the medial plane. The femur is taphonomically deformed. The fourth trochanter is developed as a non-prominent posteromedial bulge. There is no prominent bulge on the proximolateral side as in titanosauriforms. After incorporation of this information in an existing data matrix for preliminary phylogenetic analysis, Patagosaurus emerges as sister taxon to Cetiosaurus, more basal to Omeisaurus and Mamenchisaurus, and more derived than Barapasaurus and Shunosaurus.

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