A new aetosaur (Archosauria, Suchia) from the Upper Triassic Pekin Formation, Deep River Basin, North Carolina, U.S.A., and its implications for early aetosaur evolution

ABSTRACTAetosaurs are an extinct clade of quadrupedal, heavily armored archosaurs that had a worldwide distribution during the Late Triassic. Aetosaur fossils from the Upper Triassic Pekin Formation in the Deep River Basin of North Carolina (U.S.A.) consist primarily of isolated osteoderms and, rarely, more associated material. Here we describe a new genus and species, <i>Gorgetosuchus pekinensis</i>, based on an associated incomplete anterior carapace, consisting of a total of 19 nearly complete paramedian and lateral osteoderms from the first 10 rows of armor as well as some associated fragments. An important feature of <i>Gorgetosuchus</i> is that an articulated fifth row of cervical osteoderms almost encloses the neck, with prominent spines on both the dorsal and lateral osteoderms. This is a novel configuration among aetosaurs. Otherwise, NCSM 21723 preserves a mosaic of character states found in <i>Longosuchus</i>, <i>Lucasuchus</i>, or both taxa while simultaneously preserving several more plesiomorphic character states, such as cervical osteoderms that are wider than long. Our reevaluation of other Pekin Formation specimens that various authors have assigned to <i>Desmatosuchus</i>, <i>Longosuchus</i>, or <i>Lucasuchus</i> confirms that some possess characteristics of <i>Lucasuchus</i>, whereas others are not generically determinate. Incorporating <i>Gorgetosuchus</i> into existing phylogenies of aetosaurs results in a reshuffling of basal aetosaur relationships, but a variety of analyses consistently place <i>Gorgetosuchus</i> as a basal desmatosuchine. Using current taxonomic practices, there are at least three aetosaur genera in the Pekin Formation: <i>Lucasuchus</i>, <i>Coahomasuchus</i>, and <i>Gorgetosuchus.</i>http://zoobank.org/urn:lsid:zoobank.org:pub:5503A4F4-85DE-4B47-9E58-6C9F903A1640 SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP

【摘要】坚蜥目（Aetosaurs）是一类已灭绝的四足、高度装甲化的主龙类，在晚三叠世时期具有全球分布范围。采自美国北卡罗来纳州深河盆地上三叠统皮金组的坚蜥化石，以孤立的骨皮板为主，仅极少数保存有关联的化石材料。本文基于一件关联保存的不完整前装甲标本，记述一新属新种*Gorgetosuchus pekinensis*：该标本包含来自前10排装甲的共计19块近乎完整的近中位骨板与侧位骨板，以及若干关联的碎块。该新属的重要特征之一为，关节连接的第五排颈椎骨皮板几乎完全包裹颈部，且背侧与侧位骨皮板均具有显著的棘突，这一构型在坚蜥类中属于首次报道。除此以外，标本编号NCSM 21723镶嵌有*Longosuchus*、*Lucasuchus*或二者共有的特征状态，同时还保留了数处更为祖征的特征，例如颈椎骨皮板宽大于长。我们对此前不同学者归属于*Desmatosuchus*、*Longosuchus*或*Lucasuchus*的其他皮金组标本进行了重新评估，结果确认部分标本具有*Lucasuchus*的特征，而其余标本无法确定其属级分类地位。将*Gorgetosuchus pekinensis*纳入现有的坚蜥类系统发育分析框架后，基底坚蜥类的亲缘关系发生了重排，但各类分析均一致将*Gorgetosuchus*置于基底链鳄亚科的演化位置。依据当前的分类学规范，皮金组至少存在三个坚蜥目属类：*Lucasuchus*、*Coahomasuchus*与*Gorgetosuchus*。本文的生命科学标识符（LSID）为：http://zoobank.org/urn:lsid:zoobank.org:pub:5503A4F4-85DE-4B47-9E58-6C9F903A1640。【补充数据】本文补充材料可通过www.tandfonline.com/UJVP免费获取。