DOI: 10.5061/dryad.w0vt4b91s
title: 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

description: 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.
description: <strong>Supplemental 1:</strong> Character
 descriptions, updated character scorings, notes on phylogenetic analyses,
 and supplemental figures. <strong>Supplemental 2:
 </strong>TXT file of master character matrix.
 <strong>Supplemental 3: </strong>TXT script for
 Bayesian phylogenetic analyses.
 <strong>Supplemental 4:</strong> TNT file for
 parsimony analyses. Same as master character matrix. Omit OTU's
 respectively for RUN 1 and RUN 2. 
 <strong>Supplemental 5:</strong> NEX file for
 Bayesian analysis RUN 1. All specimens of
 <em>Calyptosuchus</em> are coded as seperate
 OTU's.  <strong>Supplemental
 6:</strong> NEX file for Bayesian analysis RUN 2. All specimens of
 <em>Calyptosuchus</em> are coded into a combined
 OTU.
description: # 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. [Access
 this dataset on Dryad](https://doi.org/10.5061/dryad.w0vt4b91s) The
 supplementary data includes .tnt, .txt, and .nex files required to
 replicate the phylogenetic analyses presented in this study. Also included
 is a .docx word file with the modified character list, modified scorings,
 and unpublished supplementary figures. All data files can be viewed in a
 standard text editor except for the .docx which requires Microsoft Word. 
 ## Description of the data and file structure 1. The Character list.docx
 contains the modified character list, modified scorings, and unpublished
 supplemental figures and tables. 2. The Master_matrix.txt contains the
 master character matrix from which the parsimony and Bayesian matrices
 used in this study are derived. This file is compatible with mesquite
 phylogenetic software. 3. The MrBayes_script.txt is the script executed in
 MrBayes that is required to run the .nex files under their specific
 parameters in MyBayes. The text file needs to be modified to execute the
 specific .nex file desired (see text file). 4. The Parsimony_matrix.tnt
 contains the matrix for the parsimony analyses performed using TNT. It is
 the same as the master matrix, but requires including or excluding select
 taxa in TNT to replicate RUNs 1 and 2. Wildcard taxa should be excluded
 for both RUNs - RUN 1 should omit *Calyptosuchus wellesi*; Run 2 should
 omit the individual PEFO, UCMP, and UMMP specimens. 5. The
 Bayes_Run1_matrix.nex is the file required for run 1 that includes all
 specimens of *Calyptosuchus* in question as individual OTUs. 6. The
 Bayes_Run2_matrix.nex is the file required for run 2 that includes all
 specimens into a single OTU of *Calyptosuchus*. ## Sharing/Access
 information Additional 3D image files of specimens used in this study are
 freely available online through Morphosource and digital repository of
 fossils of the University of Michigan Museum of Paleontology. Morphosource
 Project 609256 includes 3D models of PEFO 46222 and 49321. *
 [https://www.morphosource.org/projects/000609256](https://www.morphosource.org/projects/000609256) University of Michigan Museum of Paleontology digital repository includes 3D surface files of UMMP 13950 and UMMP 7470. * [https://umorf.ummp.lsa.umich.edu/wp/class-reptilia/](https://umorf.ummp.lsa.umich.edu/wp/class-reptilia/) ## Code/Software The parsimony analyses were performed using TNT v.1.5. The Bayesian inference analyses were performed using MrBayes v.3.2.6.