School of Geography, Earth & Environmental Sciences, University of Birmingham, Birmingham, UK.
Fossil Reptiles, Amphibians and Birds Section, Natural History Museum, London, UK.
Anat Rec (Hoboken). 2024 Apr;307(4):1390-1420. doi: 10.1002/ar.25316. Epub 2023 Sep 21.
The fissure fill localities of southwest England and South Wales are well-known for preserving rich assemblages of predominantly small-bodied Late Triassic to Early Jurassic tetrapods, but many aspects of these assemblages remain contentious. The age of the Late Triassic fissures is disputed, with some lines of argument suggesting a latest Triassic (Rhaetian) age, whereas other evidence suggests they may be as old as Carnian. The fissures have been hypothesized by some workers to have formed on an archipelago, with island effects invoked to explain aspects of the assemblages such as the abundance of small-bodied species. Procolophonids were a successful group of Triassic parareptiles, best known from Early to early Late Triassic assemblages, but have only recently been described from one of the fissure fill sites (Ruthin) based upon fragmentary remains. Here, we describe new procolophonid specimens from another fissure (Cromhall) that represent at least six individuals of different sizes, with much of the skeleton represented including well-preserved skull material. The Cromhall procolophonid shows strong similarities to Late Triassic procolophonids from Scotland, Brazil and North America, but both autapomorphies and a unique character combination demonstrate that it represents a new species, which we name as Hwiccewyrm trispiculum gen. et sp. nov. Phylogenetic analysis places Hwiccewyrm in a derived clade within Leptopleuroninae, together with Leptopleuron, Hypsognathus, and Soturnia. The largest specimens of Hwiccewyrm demonstrate a body size that is similar to Leptopleuron and Hypsognathus, supporting other recent work that has questioned the insular dwarfism hypothesis for the fissure fill assemblages.
英格兰西南部和南威尔士的裂隙填充地点以保存丰富的主要为小型晚三叠世至早侏罗世四足动物组合而闻名，但这些组合的许多方面仍然存在争议。这些裂隙的时代存在争议，一些观点认为它们属于最晚的三叠纪（瑞提安期），而其他证据表明它们可能与卡尼期一样古老。一些研究人员假设这些裂隙是在一个群岛上形成的，岛屿效应被用来解释组合的某些方面，例如小体型物种的丰富度。原蜥脚形类是三叠纪副爬行动物的一个成功类群，它们最著名的是来自早到晚三叠世的组合，但直到最近才根据一些零碎的遗骸从其中一个裂隙填充地点（鲁辛）被描述。在这里，我们描述了来自另一个裂隙（克罗马尔）的新原蜥脚形类标本，这些标本代表了至少六个不同大小的个体，大部分骨骼都有代表，包括保存完好的头骨材料。克罗马尔原蜥脚形类与来自苏格兰、巴西和北美的晚三叠纪原蜥脚形类有很强的相似性，但无论是独特的形态特征还是独特的特征组合都表明它代表了一个新的物种，我们将其命名为 Hwiccewyrm trispiculum 属种。系统发育分析将 Hwiccewyrm 置于 Leptopleuroninae 中的一个衍生分支内，与 Leptopleuron、Hypsognathus 和 Soturnia 一起。Hwiccewyrm 的最大标本显示出与 Leptopleuron 和 Hypsognathus 相似的体型，支持了最近其他一些质疑裂隙填充组合的岛屿侏儒假说的工作。
