Data from: Reassessment of the non-titanosaurian somphospondylan Wintonotitan wattsi (Dinosauria: Sauropoda: Titanosauriformes) from the mid-Cretaceous Winton Formation, Queensland, Australia

Wintonotitan wattsi, a Cretaceous titanosauriform sauropod from central Queensland, Australia, is redescribed following a full revision of its osteology. The holotype specimen, a partial postcranial skeleton derived from the lower Upper Cretaceous Winton Formation, comprises axial and appendicular elements. Wintonotitan has been commonly resolved as a non-titanosaurian somphospondylan titanosauriform since its description, in contrast to its more derived contemporary Diamantinasaurus matildae. We provide a detailed redescription, taking this opportunity to correct four misinterpretations made in the original description of Wintonotitan that impact on our understanding of this taxon: the right ulna was originally described as the left and vice versa; the left metacarpus was incorrectly described as being from the right side; metacarpal IV was described as metacarpal V and vice versa; and the ilium was incorrectly oriented. The reassessment of the metacarpus is particularly important, since it shows that a proximal fossa is present on metacarpals I, II and III, which might have been occupied by either the strongly convex distal end of the radius or a (possibly unossified) carpal element. We provide a review of titanosauriform metacarpal morphology to support our reassessments. Our revision of the osteology of Wintonotitan results in the identification of several previously unrecognized autapomorphies, augmenting and revising its original diagnosis. We provide additional support for the previous referral of four caudal vertebrae from south-east of Winton, Queensland, to W. wattsi. Furthermore, we demonstrate that a tentative report of titanosaur osteoderms from the Winton Formation was based on misidentification of dorsal vertebral neural spines pertaining to the holotype of W. wattsi. Consequently, titanosaur osteoderms are currently unknown from Australia. Following our revision and reinterpretation of a number of elements, we re-examine the phylogenetic placement of Wintonotitan, supporting its position as a non-titanosaurian somphospondylan titanosauriform, with no close relationship with the contemporaneous lithostrotian titanosaur Diamantinasaurus.

澳大利亚昆士兰州（Queensland）中部的白垩纪（Cretaceous）泰坦龙形类（titanosauriform）蜥脚类恐龙温顿泰坦龙（Wintonotitan wattsi），经其骨解剖学（osteology）全面修订后被重新描述。其正模标本（holotype specimen）为采自上白垩统（Upper Cretaceous）温顿组（Winton Formation）的部分颅后骨骼（postcranial skeleton），包含轴骨与附肢骨元素。自被正式命名以来，温顿泰坦龙通常被归入非泰坦龙类的索普隆达类（somphospondylan）泰坦龙形类，这与其更为衍生的同期类群迪亚曼蒂纳龙（Diamantinasaurus matildae）形成鲜明差异。本次研究对其开展了详细的重新描述，并借此修正了温顿泰坦龙原始描述中存在的四项会影响该类群认知的误释：其一，原始描述将右尺骨（ulna）误记为左尺骨，反之亦然；其二，左侧掌骨（metacarpus）被错误标注为右侧来源；其三，第四掌骨（metacarpal IV）与第五掌骨（metacarpal V）被相互颠倒；其四，髂骨（ilium）的定向出现错误。其中掌骨的重新评估尤为关键，研究显示第一、第二与第三掌骨均存在近端窝（proximal fossa），该窝可能容纳高度凸出的桡骨（radius）远端，或是未骨化的腕骨元素（carpal element）。为支撑本次重新评估，我们还对泰坦龙形类的掌骨形态学特征进行了综述。本次对温顿泰坦龙骨解剖学的修订，识别出多项此前未被发现的独有衍征（autapomorphies），完善并修订了其原始鉴别特征。我们进一步佐证了此前将昆士兰州温顿东南部发现的四块尾椎（caudal vertebrae）归入W. wattsi的结论。此外，本次研究证实，此前关于温顿组发现泰坦龙类骨皮板（osteoderms）的推测性报道，实则是误将温顿泰坦龙正模标本的背椎神经棘（dorsal vertebral neural spines）当作了骨皮板。因此，目前澳大利亚境内尚无泰坦龙类骨皮板的可靠记录。在对诸多骨骼元素进行修订与重新解释后，我们重新检验了温顿泰坦龙的系统发育位置，证实其属于非泰坦龙类的索普隆达类泰坦龙形类，与同时代的岩盔龙类（lithostrotian）泰坦龙迪亚曼蒂纳龙并无近缘关系。