Data from: A new Late Cretaceous iguanomorph from North America and the origin of New World Pleurodonta (Squamata, Iguania)

Iguanomorpha (stem + crown Iguania) is a diverse squamate clade with members that predominate many modern American lizard ecosystems. However, the temporal and palaeobiogeographic origins of its constituent crown clades (e.g. Pleurodonta (basilisks, iguanas, and their relatives)) are poorly constrained, mainly due to a meagre Mesozoic-age fossil record. Here, we report on two nearly complete skeletons from the Late Cretaceous (Campanian) of North America that represent a new and relatively large-bodied and possibly herbivorous iguanomorph that inhabited a semi-arid environment. The new taxon exhibits a mosaic of anatomical features traditionally used in diagnosing Iguania and non-iguanian squamates (i.e. Scleroglossa; e.g. parietal foramen at the frontoparietal suture, astragalocalcaneal notch in the tibia, respectively). Our cladistic analysis of Squamata revealed a phylogenetic link between Campanian-age North American and East Asian stem iguanomorphs (i.e. the new taxon + Temujiniidae). These results and our evaluation of the squamate fossil record suggest that crown pleurodontans were restricted to the low-latitude Neotropics prior to their early Palaeogene first appearances in the mid-latitudes of North America.

鬣蜥形类（Iguanomorpha，包含基干类群+冠群鬣蜥亚目Iguania）是一个物种多样性丰富的有鳞类支系，其成员在诸多现代美洲蜥蜴的生态系统中占据主导地位。然而，其所含冠群支系（例如侧齿蜥类Pleurodonta，涵盖冠蜥、鬣蜥及其近缘类群）的时间与古生物地理学起源目前限定性较差，这主要归因于中生代化石记录的极度稀缺。本文报道了两件产自北美白垩纪晚期（坎潘期）的近乎完整的骨骼化石，它们代表一种全新的、体型相对较大的鬣蜥形类，该类群可能为植食性，栖息于半干旱环境。该新分类单元兼具传统上分别用于诊断鬣蜥亚目与非鬣蜥类有鳞类（即硬舌亚目Scleroglossa）的镶嵌解剖特征：前者为额顶骨缝处的顶骨孔，后者为胫骨上的距跟骨切迹。我们针对有鳞类开展的分支系统学分析显示，坎潘期北美与东亚的基干鬣蜥形类（即该新分类单元+铁木蜥科Temujiniidae）之间存在系统发育关联。结合我们对有鳞类化石记录的评估，上述结果表明冠群侧齿蜥类在古近纪早期首次现身北美中纬度地区之前，其分布仅局限于低纬度新热带区。