Pareiasaurs were globally distributed, abundant, herbivorous parareptiles with the basal-most members found only in the mid-Permian of South Africa. These basal forms form a monophyletic group and were locally abundant and became extinct at the top of the Tapinocephalus Assemblage Zone at the end of the Guadalupian. Four species of basal pareiasaurs are currently recognised: Bradysaurus baini, B. seeleyi, Embrithosaurus schwarzi and Nochelesaurus alexanderi, but they are all poorly understood and there remains historic uncertainty as to their validity. In this paper, our second contribution designed to improve understanding of the basal group, we present the first detailed cranial description and updated diagnosis for Nochelesaurus alexanderi and demonstrate that it is a distinct taxon based on one cranial autapomorphy, a large transversely wide postparietal, and a combination of cranial characters. Within the local group of mid-Permian pareiasaurs, we recognise new dental features of Nochelesaurus alexanderi: non-symmetrical marginal cusp arrangements on upper and lower teeth resulting from an extra basal mesial cusp; an incipient horizontal cingulum on lower jaw teeth, sometimes with one or two tiny medial cingular cusps; and up to ten marginal cusps. Our study demonstrates that tooth morphology and orientation, cranial ornamentation, morphology of the cheek bosses, shape of the postfrontal and postparietal, and morphology of the distal paroccipital process of the opisthotic are the most useful to identify South African mid-Permian pareiasaurs.

中文翻译：

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南非卡鲁盆地中二叠纪pareiasaur Nochelesaurus alexanderi的颅骨形态

Pareiasaurs 是全球分布的、丰富的草食性副爬行动物，其中基部最多的成员仅在南非二叠纪中期发现。这些基础形式形成一个单系群，在当地很丰富，并在顶部灭绝貘头目瓜达卢皮亚尽头的聚集区。目前已知有四种基础类龙目：Bradysaurus baini, B. seeleyi,长尾龙和亚历山大诺切列龙，但它们都知之甚少，而且它们的有效性仍然存在历史上的不确定性。在本文中，我们的第二个贡献旨在提高对基础组的理解，我们提出了第一个详细的颅骨描述和更新的诊断亚历山大诺切列龙并证明它是一个独特的分类单元，基于一个颅骨自体形态、一个大的横向宽顶骨和颅骨特征的组合。在当地的二叠纪中期龙类群中，我们发现了新的牙齿特征亚历山大诺切列龙：由额外的基部近中牙尖导致的上下牙齿的不对称边缘牙尖排列；下颌牙齿上的早期水平扣带回，有时带有一两个微小的内侧扣带回尖；和多达十个边缘尖。我们的研究表明，牙齿形态和方向、颅骨装饰、脸颊隆起的形态、后额叶和顶叶的形状以及角骨远端枕骨突的形态是识别南非二叠纪中二叠纪恐龙最有用的方法。