Cranial anatomy, intraspecific variation, and positional variation within Calyptosuchus wellesi (Pseudosuchia: Aetosauria) based on new specimens from the Upper Triassic Chinle Formation (Adamanian, early middle-Norian) of Petrified Forest National Park, Arizona, USA

Calyptosuchus wellesi is an aetosaur known from the upper Blue Mesa Member and lowermost Sonsela Member of the Chinle Formation in Arizona, and the Tecovas Formation of the Dockum Group, Texas. The taxon is considered biostratigraphically informative and aids in correlating Upper Triassic strata across the southwestern United States. Our anatomical understanding of Calyptosuchus was primarily based on the holotype specimen from Texas and referred specimens, including several disarticulated elements from the Placerias Quarry in northern Arizona. We provide a re-interpretation of the holotype specimen and describe two new specimens referrable to Calyptosuchus from northern Arizona. Together these specimens provide new information on the cranial anatomy, including dentition, and the positional and intraspecific variation within the carapace and vertebral column, respectively, of the taxon. This new evidence suggests that the skull anatomy of Calyptosuchus is more similar to that of Neoaetosauroides and Stagonolepis than to other aetosaurs. The dentition of Calyptosuchus supports recent hypotheses suggesting that aetosaurs were more omnivorous/faunivorous. The associated carapace expands our anatomical understanding of characters that vary among trunk paramedian osteoderms. We identify variation in the vertebral column within the trunk region, including the prominence of the centrodiapophyseal lamina and anatomy of the neural spine. Additionally, we report the first documentation of co-ossified sacral vertebrae within Calyptosuchus, which is also the first observation of this state within the Aetosauria outside of the Desmatosuchini. This suggests that co-ossification of the sacral vertebrae may be more prevalent within the Aetosauria than previously recognized.

Methods
Supplemental 1: Character descriptions, updated character scorings, notes on phylogenetic analyses, and supplemental figures.

Supplemental 2: TXT file of master character matrix.

Supplemental 3: TXT script for Bayesian phylogenetic analyses.

Supplemental 4: TNT file for parsimony analyses. Same as master character matrix. Omit OTU's respectively for RUN 1 and RUN 2. 

Supplemental 5: NEX file for Bayesian analysis RUN 1. All specimens of Calyptosuchus are coded as seperate OTU's. 

Supplemental 6: NEX file for Bayesian analysis RUN 2. All specimens of Calyptosuchus are coded into a combined OTU.

Calyptosuchus wellesi是一种坚蜥类（Aetosaur），其化石发现于美国亚利桑那州钦利组（Chinle Formation）的上部蓝台地段（upper Blue Mesa Member）和最低层桑塞拉段（lowermost Sonsela Member），以及德克萨斯州多库姆群（Dockum Group）的特科瓦组（Tecovas Formation）。该分类单元被认为具有生物地层学指示价值，有助于对比美国西南部的上三叠统地层。我们对Calyptosuchus wellesi的解剖学认知主要基于产自德克萨斯州的正模标本（holotype specimen）以及归入标本（referred specimens），其中包括产自亚利桑那州北部普莱塞里亚斯采石场（Placerias Quarry）的多件离散骨骼元素。本文对该正模标本进行了重新解读，并描述了两件产自亚利桑那州北部的归入Calyptosuchus wellesi的新标本。上述标本共同为该类群的颅部解剖结构（包括齿列）、背甲的位置变异以及脊柱的种内变异提供了新的研究数据。这一新证据表明，Calyptosuchus wellesi的颅部解剖结构与新坚蜥属（Neoaetosauroides）和斯通哥鳄属（Stagonolepis）的相似性高于其他坚蜥类。Calyptosuchus wellesi的齿列支持了近期提出的假说，即坚蜥类的食性更偏向杂食性/食肉性。与之关联的背甲拓展了我们对躯干副中骨板（trunk paramedian osteoderms）间性状变异的解剖学认知。我们识别出躯干区域脊柱存在变异，包括中椎横突板（centrodiapophyseal lamina）的突出程度以及神经棘（neural spine）的解剖结构。此外，本文首次报道了Calyptosuchus wellesi内存在愈合荐椎（co-ossified sacral vertebrae）的现象，这也是坚蜥目（Aetosauria）内除德沙莫鳄族（Desmatosuchini）之外首次观察到该特征状态。该发现表明，荐椎愈合在坚蜥目中的普及程度可能比此前认知的更高。

方法
补充材料1：性状描述、更新的性状编码、系统发育分析说明以及补充图版。
补充材料2：主性状矩阵的TXT文件。
补充材料3：贝叶斯系统发育分析的TXT脚本。
补充材料4：用于简约法分析的TNT文件，与主性状矩阵一致。运行1和运行2需分别省略对应的操作分类单元（Operational Taxonomic Unit，简称OTU）。
补充材料5：贝叶斯分析运行1的NEX文件。所有Calyptosuchus wellesi标本均被编码为独立的OTU。
补充材料6：贝叶斯分析运行2的NEX文件。所有Calyptosuchus wellesi标本被合并为一个OTU。