Data from: A new Hyperodapedon (Archosauromorpha, Rhynchosauria) from the Upper Triassic of India: implications on Rynchosaur phylogeny

A new species of the rhynchosaur genus Hyperodapedon, namely H. tikiensis, is described from well-preserved skeletal elements that were collected from the Upper Triassic Tiki Formation of India. Hyperodapedon tikiensis is diagnosed on the basis of several cranial and postcranial features including longer than wide basipterygoid process, crest-shaped maxillary cross section lateral to the main longitudinal groove, deeply excavated neural arches of mid-dorsal vertebrae, long scapular blade, a pronounced deltopectoral crest, proximal humeral end much broader than distal end, iliac length greater than iliac height, equal pre- and postacetabular iliac lengths and circular femoral cross section. Two distinct morphotypes of the maxillary tooth plates can be discerned, which are attributed to ontogenetic variations. A maximum-parsimony analysis was carried out to show that the order Rhynchosauria is characterized by nine cranial and one postcranial character states. The analysis reveals that Otischalkia elderae is invalid and the basal forms, Howesia and Mesosuchus, are closely related. The Mid-Triassic genus Ammorhynchus is more derived and forms a sister group to the Late Triassic subfamily Hyperodapedontinae. Isalorhynchus and Teyumbaita are basal to the pandemic genus Hyperodapedon. Twenty-four characters that are not homoplasious document major patterns of skeletal evolution in rhynchosaurs. From laterally oriented scapula and slender propodials, the postcranial skeleton evolved into a more robust form as is evident from nearly vertical scapula and increase in the robustness of the propodials. Shortening of the femur is noted in the derived Late Triassic forms as exemplified in Hyperodapedon gordoni, Hyperodapedon huxleyi and H. tikiensis.本文记述了产自印度上三叠统蒂基组（Upper Triassic Tiki Formation）、以保存完好的骨骼化石为依据的喙头龙（rhynchosaur）异平齿龙属（Hyperodapedon）一新种——蒂基异平齿龙（H. tikiensis）。 蒂基异平齿龙可通过以下多项颅区与颅后骨骼特征进行鉴定：基翼突长大于宽、主纵沟外侧的上颌骨横截面呈嵴状、中部背椎的神经弓深陷、肩胛叶较长、具显著的三角胸嵴、肱骨近端远宽于远端、髂骨长大于高、髋臼前髂骨段与髋臼后髂骨段长度相等、股骨横截面呈圆形。 研究中可识别出两种截然不同的上颌齿板形态型，该差异被归因于个体发育变异。 本次开展的最大简约法分析（maximum-parsimony analysis）显示，喙头龙目（Rhynchosauria）具有9项颅区及1项颅后特征状态。分析结果表明，奥蒂斯查尔克龙（Otischalkia elderae）为无效分类单元，基干类群霍西西亚龙（Howesia）与中鳄龙（Mesosuchus）亲缘关系密切。 中三叠世属阿莫林喙龙（Ammorhynchus）演化程度更高，为晚三叠世异平齿龙亚科（Hyperodapedontinae）的姊妹群。伊萨洛喙龙（Isalorhynchus）与泰姆巴伊塔龙（Teyumbaita）为广布属异平齿龙属（Hyperodapedon）的基干类群。 24项非同源性（homoplasious）特征阐明了喙头龙类骨骼演化的主要模式：早期类群的肩胛骨呈侧向排列、肢杆骨（propodials）纤细，而演化后期类群的肩胛骨近乎垂直、肢杆骨粗壮度提升，体现出颅后骨骼向更粗壮的形态演化。 在演化衍生的晚三叠世类群中可见股骨缩短现象，以戈氏异平齿龙（Hyperodapedon gordoni）、赫胥黎异平齿龙（Hyperodapedon huxleyi）以及蒂基异平齿龙为代表。