Scheyer Torsten M, Spiekman Stephan N F, Sues Hans-Dieter, Ezcurra Martín D, Butler Richard J, Jones Marc E H
Universität Zürich, Paläontologisches Institut und Museum, Karl Schmid-Strasse 4, Zurich CH-8006, Switzerland.
Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, MRC 121, Washington, DC 20560, USA.
R Soc Open Sci. 2020 Mar 25;7(3):192179. doi: 10.1098/rsos.192179. eCollection 2020 Mar.
Correctly identifying taxa at the root of major clades or the oldest clade-representatives is critical for meaningful interpretations of evolution. A small, partially crushed skull from the Late Triassic (Norian) of Connecticut, USA, originally described as an indeterminate rhynchocephalian saurian, was recently named and reinterpreted as sister to all remaining Rhynchosauria, one of the earliest and globally distributed groups of herbivorous reptiles. It was also interpreted as having an exceptionally reinforced snout and powerful bite based on an especially large supratemporal fenestra. Here, after a re-analysis of the original scan data, we show that the skull was strongly dorsoventrally compressed post-mortem, with most bones out of life position. The cranial anatomy is consistent with that of other rhynchocephalian lepidosauromorphs, not rhynchosaurs. The 'reinforced snout' region and the 'exceptionally enlarged temporal region' are preservational artefacts and not exceptional among clevosaurid rhynchocephalians. is thus not a key taxon for understanding diapsid feeding apparatus evolution.
正确识别主要分支根部的分类群或最古老的分支代表对于有意义地解释进化至关重要。一个来自美国康涅狄格州晚三叠世（诺利期）的小型、部分破碎的头骨，最初被描述为一种不确定的喙头目蜥蜴，最近被命名并重新解释为所有其余喙头龙类的姐妹群，喙头龙类是最早且分布于全球的草食性爬行动物群体之一。基于一个特别大的上颞孔，它还被解释为具有异常强化的吻部和强大的咬合力。在此，在对原始扫描数据进行重新分析后，我们表明该头骨在死后受到强烈的背腹向挤压，大多数骨头脱离了生前位置。其颅骨解剖结构与其他喙头目鳞龙形类一致，而非喙头龙类。“强化吻部”区域和“异常扩大的颞部区域”是保存假象，在楔齿龙类喙头目中并非异常。因此，它不是理解双孔类进食器官进化的关键分类群。
