DOI: 10.5061/dryad.r7sqv9s81
title: A comprehensive anatomical and phylogenetic evaluation of Dilophosaurus wetherilli (Dinosauria: Theropoda) with descriptions of new specimens from the Kayenta Formation of northern Arizona

description: Dilophosaurus wetherilli was the largest animal known to have lived on
 land in North America during the Early Jurassic. Despite its charismatic
 presence in pop culture and dinosaurian phylogenetic analyses, major
 aspects of the skeletal anatomy, taxonomy, ontogeny, and evolutionary
 relationships of this dinosaur remain unknown. Skeletons of this species
 were collected from the middle and lower part of the Kayenta Formation in
 the Navajo Nation of Arizona. Redescription of the holotype, referred, and
 previously undescribed specimens of Dilophosaurus wetherilli supports the
 existence of a single species of crested, large-bodied theropod in the
 Kayenta Formation. The parasagittal nasolacrimal crests are uniquely
 constructed by a small ridge on the nasal process of the premaxilla,
 dorsoventrally-expanded nasal, and tall lacrimal that includes a posterior
 process behind the eye. The cervical vertebrae exhibit serial variation
 within the posterior centrodiapophyseal lamina, which bifurcates and
 reunites down the neck. Iterative specimen-based phylogenetic analyses
 result in each of the additional specimens recovered as the sister taxon
 to the holotype. When all five specimens are included in an analysis, they
 form a monophyletic group that supports the monotypy of the genus.
 Dilophosaurus wetherilli is not recovered as a ceratosaur or coelophysoid
 but is instead a non-averostran neotheropod in a grade with other
 stem-averostrans like Cryolophosaurus ellioti and Zupaysaurus rougieri. We
 do not recover a monophyletic ‘Dilophosauridae.’ Instead of being
 apomorphic for a small clade of early theropods, it is more likely that
 elaboration of the nasals and lacrimals of stem-averostrans is
 plesiomorphically present in early ceratosaurs and tetanurans that share
 those features. Many characters of the axial skeleton of Dilophosaurus
 wetherilli are derived compared to Late Triassic theropods and may be
 associated with macropredation and an increase in body size in Theropoda
 through the Triassic-Jurassic boundary.
description: <strong>Supplemental Data 1</strong>: Linear
 measurements less than 200 mm were measured using Pittsburgh electronic
 digital calipers.  Lengths longer than 200 mm were measured using a paper
 tape measure. All measurements are in mm unless otherwise noted.
 Measurements with * denote those taken off of broken surfaces and should
 be considered minimum distances. When two numbers are present, the first
 represents the left side and the second represents the right. A single
 number results from midline elements or the only preserved element in that
 specimen. See description for details.
 <strong>Supplemental Data 2</strong>: Character
 descriptions for the phylogenetic analyses.
 <strong>Supplemental Data 3</strong>: The braincase
 of TMM 47006-1 was scanned at the University of Texas High-Resolution
 X-ray CT Facility using a North Star Imaging scanner that comprises a Fein
 Focus High Power 200 kV source (0.24 mA), aluminum filter, and Perkin
 Elmer detector. The voxel size was 50.5 microns, resulting in 1733 total
 slices. A post-reconstruction ring correction was applied to slices
 1420-1733. Segmentation, image processing, and surface-file editing were
 accomplished using VGStudio Max (version 2.0.1) and Meshmixer (version
 3.3.15). <strong>Supplemental Data
 4</strong>: TNT file for the phylogenetic analyses.
 <strong>Supplemental Data 5</strong>: TNT outputs for
 the six phylogenetic analyses (MPTs, apomorphy lists, consensus trees, and
 support values).
description: The UCMP, MNA, and TMM specimens in this study are property of
 the Navajo Nation and are held in trust at the University of California
 Museum of Paleontology (Berkeley, CA), the Museum of Northern Arizona
 (Flagstaff, AZ), and the Texas Vertebrate Paleontology Collections at The
 University of Texas at Austin (Austin, TX). Please acknowledge the Navajo
 Nation when referring to these specimens. Any persons
 wishing to conduct geologic investigations on the Navajo Nation must first
 apply for and receive a permit from, P.O. Box 1910, Window Rock, AZ 86515
 and telephone number (928) 871-6587.