The endocast of Phuwiangosaurus sirindhornae from the Lower Cretaceous of Thailand

Among skeletons, the cranial elements of sauropod are typically fragmented and rare, despite the increasing number of elements and almost complete skulls discovered or redescribed in the last decades. Phuwiangosaurus sirindhornae was one of the most completely sauropod braincase known from South -east Asia. Here we describe an endocast of Phuwiangosaurus, including the hindbrain, cranial nerves, blood vessels, and inner ear. The shape of the dural peak was similar to Camarasaurus and the bulbous feature of the pituitary gland was similar to basal titanosaur. The trigeminal nerve exits the braincase through more than one opening. The abducens nerve passes the pituitary fossa laterocaudally, and the hypoglossal nerve exiting the braincase through two canals as in Sarmientosaurus, some titanosaurs, and early-branching macronarians. There is, one exit of CN XII on each side of the occipital condyle as in advanced titanosaurs. The anterior semicircular canal is elevated dorsally and larger than the posterior semicircular canal similar to Giraffatitan, Malawisaurus, Sarmientosaurus and Diamantinasaurus. Our observations are congruent with the interpretation of Phuwiangosaurus is a transitional form between the somphospondylan and titanosaurian despite some works put it in a basal position within som-phospondylan sauropods.(c) 2022 Elsevier Ltd. All rights reserved.