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 坚蜥类（Aetosaur）是一类已灭绝的四足重甲主龙类（archosaur），在三叠纪晚期曾广泛分布于全球。采自美国北卡罗来纳州深河盆地上三叠统皮金组的坚蜥类化石，主要以孤立的骨板（osteoderm）为主，仅极少数为关联保存的标本。本次研究基于一件关联保存的不完整前部背甲，记述一新属新种——皮金项饰鳄（*Gorgetosuchus pekinensis*），该标本包含来自前10排护甲的19块近乎完整的亚中线骨板与侧位骨板，以及若干关联碎片。项饰鳄属的关键鉴别特征为：关节连接的第五排颈骨板几乎完全包裹颈部，其背侧与侧位骨板均具显著棘突，这一构型在坚蜥类中属于全新的形态特征。此外，标本NCSM 21723镶嵌了兼具长鳄属（*Longosuchus*）、卢卡鳄属（*Lucasuchus*）或二者的部分性状特征，同时还保留了若干更为原始的祖征性状，例如颈骨板宽大于长。本次研究对此前不同学者归入链鳄属（*Desmatosuchus*）、长鳄属（*Longosuchus*）或卢卡鳄属（*Lucasuchus*）的其他皮金组标本进行了重新评估，确认其中部分标本具备卢卡鳄属的特征，其余标本则无法确定其属级分类地位。将项饰鳄属纳入现有的坚蜥类系统发育框架后，基底坚蜥类的系统发育关系发生了重排，但各类分析均一致支持项饰鳄属属于基底链鳄亚科（desmatosuchine）。按照当前分类学规范，皮金组中至少存在3个坚蜥类属：卢卡鳄属（*Lucasuchus*）、科阿韦拉鳄属（*Coahomasuchus*）与项饰鳄属（*Gorgetosuchus*）。本文的Zoobank公开标识为：urn:lsid:zoobank.org:pub:5503A4F4-85DE-4B47-9E58-6C9F903A1640。补充材料——本文的补充材料可通过www.tandfonline.com/UJVP免费获取。