PHYLOGENETIC RELATIONSHIPS OF THE EUROPEAN TRILOPHOSAURIDS TRICUSPISAURUS THOMASI AND VARIODENS INOPINATUS
PHYLOGENETIC RELATIONSHIPS OF THE EUROPEAN TRILOPHOSAURIDS TRICUSPISAURUS THOMASI AND VARIODENS INOPINATUS
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DOI：
10.1080/02724634.2021.1999250
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发表时间：
2021-07-04
影响因子：
1.4
通讯作者：
Rayfield, Emily J.
中科院分区：
文献类型：
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作者：
Chambi-Trowell, Sofia A. V.;Whiteside, David I.;Rayfield, Emily J.
三叶龙科是北美洲西部和新斯科舍省上三叠世的一种已灭绝的原蜥脚类。在英国西南部的上三叠统裂缝填塞物中，根据它们的多尖牙牙齿，也报道了可能的三叉龙-托马西三角龙和伊诺瓦龙。在这里，我们提供了一个更新的描述inopinatus，并添加到T. thomasi的描述，包括重新检查其全型牙齿的CT扫描。我们确认，牙髓上明显的间隙是病理性的，间隙两侧牙齿的牙本质不对称地厚，并且牙髓前部的大量血管化证实它可能有角化性鼻黏膜。我们的进化分析，其中我们增加了9个新特征，证实了T. thomasi和V. inopinatus是密切相关的分类群，是已知最年轻的三头龙。此外，我们支持先前的一个建议，即这两种欧洲三叉龙的相对较小的尺寸是由岛屿侏儒症造成的。
Trilophosauridae are an extinct group of archosauromorphs from the Upper Triassic of western North America and Nova Scotia. Possible trilophosaurids Tricuspisaurus thomasi and Variodens inopinatus have also been reported from Upper Triassic fissure fills in the southwest of the United Kingdom, based on their multi-cuspid dentitions. Here, we provide an updated description of V. inopinatus and add to the description of T. thomasi, including re-examining CT scans of its holotype dentary. We confirm that the apparent gap on the dentary of T. thomasi is pathological, with the dentine of the teeth on either side of the gap asymmetrically thick, and that heavy vascularization of the anterior part of the dentary confirms it likely had a keratinous rhamphotheca. Our cladistic analyses, to which we add nine new characters, confirm that T. thomasi and V. inopinatus are closely related taxa and the youngest known trilophosaurids. Further, we support a previous suggestion that the relatively small size of these two European trilophosaurids results from insular dwarfism.