A reassessment of Mongolosaurus haplodon Gilmore, 1933, a titanosaurian sauropod dinosaur from the Early Cretaceous of Inner Mongolia, People's Republic of China

作者：Mannion Philip D^*

来源：Journal of Systematic Palaeontology, 2011, 9(3): 355-378.

DOI：10.1080/14772019.2010.527379

• Asia
• convergent evolution
• Mesozoic
• Mongolosaurus
• phylogeny
• systematics

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 the limited material, but also reflects the unusual combination of basal and derived features for this clade and the need for a better understanding of titanosaur intra-relationships. Reassessment of this animal provides new information on the atlas-axis complex, which is extremely poorly known in titanosaurs, and highlights several new characters that may prove useful in future phylogenetic analyses, such as the ratio of the transverse widths of the basal tubera and occipital condyle. A number of features pertaining to both the cranial material and cervical vertebrae are similar to those seen in some diplodocoids (including an anteroventral projection on the atlantal intercentrum and distal bifurcation of anterior cervical neural spines), providing further evidence for convergence between these two major neosauropod radiations. Other remains previously attributed to Mongolosaurus from China and Russia cannot be referred to this genus. In summary, Mongolosaurus represents one of the earliest known titanosaurs from eastern Asia and adds to our understanding of this diverse clade of sauropods.

• 出版日期2011