Parker William G
Division of Resource Management, Petrified Forest National Park, Petrified Forest, Arizona, United States; Jackson School Museum of Earth History, University of Texas at Austin, Austin, Texas, United States.
PeerJ. 2016 Aug 30;4:e2411. doi: 10.7717/peerj.2411. eCollection 2016.
Aetosaurians are some of the most common fossils collected from the Upper Triassic Chinle Formation of Arizona, especially at the Petrified Forest National Park (PEFO). Aetosaurians collected from lower levels of the park include Desmatosuchus spurensis, Paratypothorax, Adamanasuchus eisenhardtae, Calyptosuchus wellesi, and Scutarx deltatylus. Four partial skeletons collected from the park between 2002 and 2009 represent the holotype and referred specimens of Scutarx deltatylus. These specimens include much of the carapace, as well as the vertebral column, and shoulder and pelvic girdles, and a new naming convention proposed for osteoderms descriptions better differentiates portions of the carapace and ventral armor. A partial skull from the holotype specimen represents the first aetosaur skull recovered and described from Arizona since the 1930s. The key morphological feature distinguishing Scutarx deltatylus is the presence of a prominent, triangular boss located in the posteromedial corner of the dorsal surface of the dorsal paramedian osteoderms. Scutarx deltatylus can be distinguished from closely related forms Calyptosuchus wellesi and Adamanasuchus eisenhardtae not only morphologically, but also stratigraphically. Thus, Scutarx deltatylus is potentially an index taxon for the upper part of the Adamanian biozone.
坚蜥类是从亚利桑那州上三叠统钦尔组采集到的最常见化石之一，尤其是在石化林国家公园（PEFO）。从该公园较低层位采集到的坚蜥类包括斯氏链鳄、副平胸龙、艾氏阿达曼蜥、韦氏盔鳄和三角洲盾甲龙。2002年至2009年间从该公园采集到的四具部分骨骼化石代表了三角洲盾甲龙的正模标本和归入标本。这些标本包括大部分背甲，以及脊柱、肩带和腰带，并且为骨板描述提出的一种新命名惯例能更好地区分背甲和腹甲的各部分。正模标本中的一个部分头骨是自20世纪30年代以来在亚利桑那州发现并描述的首个坚蜥类头骨。区分三角洲盾甲龙的关键形态特征是在背中线上方骨板背面的后内侧角处有一个突出的三角形凸起。三角洲盾甲龙不仅在形态上，而且在地层上都能与亲缘关系较近的韦氏盔鳄和艾氏阿达曼蜥区分开来。因此，三角洲盾甲龙可能是阿达曼生物带上部的一个标志分类单元。
