A reassessment ofMongolosaurus haplodonGilmore, 1933, a titanosaurian sauropod dinosaur from the Early Cretaceous of Inner Mongolia, People's Republic of China
The Early Cretaceous of China has yielded a diverse sauropod fauna, dominated by basal titanosauriforms. Known from a basicranium, teeth and the first three cervical vertebrae, Mongolosaurus haplodon is a poorly understood taxon whose evolutionary relationship to other sauropods has remained uncertain. Redescription of Mongolosaurus identifies key features that confirm its titanosaurian affinities and demonstrate its validity, based on several autapomorphies and a unique combination of characters. Diagnostic features include: a low neural spine which does not extend above the epipophyses; the dorsal edges of the posterior articular surfaces of anterior cervical vertebrae projecting more posteriorly than the ventral edges; and postaxial spinoprezygapophyseal laminae forming a dorsoventrally elongate X-shape in anterior view. Mongolosaurus is incorporated into three independent cladistic analyses; however, its precise phylogenetic position within Titanosauria remains unclear. This is partly a consequence of...