DOI: 10.5061/dryad.31726
title: Data from: A basal lithostrotian titanosaur (Dinosauria: Sauropoda) with a complete skull: implications for the evolution and paleobiology of Titanosauria

description: We describe Sarmientosaurus musacchioi gen. et sp. nov., a titanosaurian
 sauropod dinosaur from the Upper Cretaceous (Cenomanian–Turonian) Lower
 Member of the Bajo Barreal Formation of southern Chubut Province in
 central Patagonia, Argentina. The holotypic and only known specimen
 consists of an articulated, virtually complete skull and part of the
 cranial and middle cervical series. Sarmientosaurus exhibits the following
 distinctive features that we interpret as autapomorphies: (1) maximum
 diameter of orbit nearly 40% rostrocaudal length of cranium; (2) complex
 maxilla–lacrimal articulation, in which the lacrimal clasps the ascending
 ramus of the maxilla; (3) medial edge of caudal sector of maxillary
 ascending ramus bordering bony nasal aperture with low but distinct ridge;
 (4) ‘tongue-like’ ventral process of quadratojugal that overlaps quadrate
 caudally; (5) separate foramina for all three branches of the trigeminal
 nerve; (6) absence of median venous canal connecting infundibular region
 to ventral part of brainstem; (7) subvertical premaxillary, procumbent
 maxillary, and recumbent dentary teeth; (8) cervical vertebrae with
 ‘strut-like’ centroprezygapophyseal laminae; (9) extremely elongate and
 slender ossified tendon positioned ventrolateral to cervical vertebrae and
 ribs. The cranial endocast of Sarmientosaurus preserves some of the most
 complete information obtained to date regarding the brain and sensory
 systems of sauropods. Phylogenetic analysis recovers the new taxon as a
 basal member of Lithostrotia, as the most plesiomorphic titanosaurian to
 be preserved with a complete skull. Sarmientosaurus provides a wealth of
 new cranial evidence that reaffirms the close relationship of titanosaurs
 to Brachiosauridae. Moreover, the presence of the relatively derived
 lithostrotian Tapuiasaurus in Aptian deposits indicates that the new
 Patagonian genus represents a ‘ghost lineage’ with a comparatively
 plesiomorphic craniodental form, the evolutionary history of which is
 missing for at least 13 million years of the Cretaceous. The skull anatomy
 of Sarmientosaurus suggests that multiple titanosaurian species with
 dissimilar cranial structures coexisted in the early Late Cretaceous of
 southern South America. Furthermore, the new taxon possesses a number of
 distinctive morphologies—such as the ossified cervical tendon, extremely
 pneumatized cervical vertebrae, and a habitually downward-facing
 snout—that have rarely, if ever, been documented in other titanosaurs,
 thus broadening our understanding of the anatomical diversity of this
 remarkable sauropod clade. The latter two features were convergently
 acquired by at least one penecontemporaneous diplodocoid, and may
 represent mutual specializations for consuming low-growing vegetation.
description: CT data for
 Sarmientosaurus craniumOriginal (DICOM format)
 computed tomographic (CT) data obtained from the cranium of the holotype
 of the titanosaurian sauropod dinosaur Sarmientosaurus musacchioi gen. et
 sp. nov. (MDT-PV 2).Sarmientosaurus_MDT-PV_2_cranium_DICOM_CT_data.zipCT data for Sarmientosaurus mandibleOriginal (DICOM format) computed tomographic (CT) data obtained from the mandible of the holotype of the titanosaurian sauropod dinosaur Sarmientosaurus musacchioi gen. et sp. nov. (MDT-PV 2).Sarmientosaurus_MDT-PV_2_mandible_DICOM_CT_data.zip