Herrera-Flores et al.—Reassessment of Clevosaurus latidens
methods outperform parsimony for morphological data (O’Reilly et al., 2016; Puttick et al., 2017), recovering more accurate, but less precise results. To clarify the doubtful taxonomic affinity of Clevosaurus
latidens, we re-examined the type specimens and other material described by Fraser (1993). We updated the character matrix of a recent phylogenetic analysis of the Rhynchocephalia (Hsiou et al., 2015), recoded morphological characters for C. latidens, and performed both parsimony and Bayesian analyses. Our results confirm that C. latidens is not related to Clevosaurus, but represents a new genus. Our phylogenetic analyses recover similar topologies using both parsimony and Bayesian approa- ches. We employ the new phylogeny to propose formal names for two higher clades within Rhynchocephalia.
Material and methods
We re-examined the type material and other material described by Fraser (1993) as Clevosaurus latidens. All specimens of C. latidens consist of fragments of dentary, maxilla, and premaxilla housed in the collections of the Virginia Museum of Natural His- tory and theUniversity of Aberdeen. For anatomical comparisons, we reviewed several specimens of Clevosaurus from the paleon- tological collections of theUniversity of Bristol and theUniversity Museum of Zoology in Cambridge. To explore the phylogenetic relationships of rhynchoce-
phalians and the position of Clevosaurus latidens, we used the largest and most up-to-date data matrix of Rhynchocephalia (Hsiou et al., 2015). We added three taxa—C. sectumsemper Klein et al., 2015, Derasmosaurus pietraroiae Barbera and Macuglia, 1988, and Priosphenodon minimus Apesteguía and Carballido, 2014—and recoded some characters for C. latidens and Pelecymala robustus Fraser, 1986 after examination of the type specimens. The new matrix comprises 47 operational taxonomic units scored for 74 characters. We rooted the trees with the lepidosauromorph Sophineta cracoviensis Evans and Borsuk-Bialynicka, 2009. Two squamates, the Late Jurassic– Early Cretaceous Eichstaettisaurus Kuhn, 1958 and the extant Pristidactylus Gray, 1845, were also used as outgroups. The revised taxon-character data matrix was analyzed
using both equally weighted maximum parsimony and Bayesian inference. Parsimony analysis was performed in TNT v. 1.5 (Goloboff et al., 2008; Goloboff and Catalano, 2016), first using the ‘New Technology’ search options. The initial tree search used multiple replications with sectorial searches, four rounds of tree fusing, 10 rounds of drifting, and 200 ratcheting iterations. Following this, the generated most parsimonious trees (MPTs) were analyzed using traditional tree bisection and reconnection branch swapping. All recovered MPTs were then summarized in a 50% majority rule consensus tree, and clade robustness was assessed with Bremer decay indices (Bremer, 1994). Bayesian inference trees were estimated using MrBayes v. 3.2 (Huelsen- beck and Ronquist, 2001; Ronquist et al., 2012). The standard Mk model (Lewis, 2001) with gamma distribution priors for site rate variation was specified. The analysis was performed with four runs of four chains, run for 108 generations, sampling parameters every 1000 generations. The first 25% of sampled trees were discarded as burn-in. Convergence was assessed based on effective sample size (ESS) values >200. Results from
735
the Bayesian analysis were summarized using a 50% majority consensus tree, revealing clades that have posterior probability values of ≥ 50%. The data matrix and analytical scripts are included in the Supplementary Data Set.
Repositories and institutional abbreviations.—AUP= University of Aberdeen Paleontology Collection; BRSUG= Bristol University, School of Earth Sciences Collection; NMS=National Museums Scotland; SAMK=South African Museum; UMZC=University Museum of Zoology, Cambridge; VMNH=Virginia Museum of Natural History.
Systematic paleontology
Superorder Lepidosauria Haeckel, 1866 Order Rhynchocephalia Günther, 1867 Suborder Sphenodontia Williston, 1925 Infraorder Eusphenodontia new infraorder
Remarks.—See Discussion. Clade Neosphenodontia new clade
Remarks.—See Discussion.
Clade Opisthodontia Apesteguía and Novas, 2003 Genus Fraserosphenodon new genus
urn:lsid:
zoobank.org:act:6C14E307-718C-47C8-AC8F- C658A048289B
Type species.—Clevosaurus latidens Fraser, 1993.
Diagnosis for the genus and only known species.—Moderate- sized rhynchocephalian. Maxillary teeth with relatively short crowns with transversely broadened posterolabial flanges with- out grooved facets on the labial surface. Robust dentary with a wide mandibular symphysis. Dentary with three generations of teeth. Front of dentary with two rounded successional teeth followed by a series of six or seven very small rounded hatch- ling teeth. Additional teeth in dentary transversely broadened distinctly triangular in labial view and rounded and bulbous in occlusal view.
Etymology.—The genus epithet is in honor of the British paleontologist Nicholas ‘Nick’ Fraser, for his outstanding contributions to the knowledge of the British Triassic fauna, especially for his exceptional work on early rhynchocephalians.
Occurrence.—Cromhall Quarry, Avon, England, site 5A of Late Triassic fissure deposit.
Remarks.—All Fraserosphenodon specimens are quite frag- mentary, but their tooth morphology, based on wide and robust teeth for grinding, clearly differs from the tooth shape for cutting and slicing characteristic of the genus Clevosaurus, and, indeed, is more similar to that of opisthodontians.
Fraserosphenodon latidens (Fraser, 1993) new combination Figures 1–2
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112 |
Page 113 |
Page 114 |
Page 115 |
Page 116 |
Page 117 |
Page 118 |
Page 119 |
Page 120 |
Page 121 |
Page 122 |
Page 123 |
Page 124 |
Page 125 |
Page 126 |
Page 127 |
Page 128 |
Page 129 |
Page 130 |
Page 131 |
Page 132 |
Page 133 |
Page 134 |
Page 135 |
Page 136 |
Page 137 |
Page 138 |
Page 139 |
Page 140 |
Page 141 |
Page 142 |
Page 143 |
Page 144 |
Page 145 |
Page 146 |
Page 147 |
Page 148 |
Page 149 |
Page 150 |
Page 151 |
Page 152 |
Page 153 |
Page 154 |
Page 155 |
Page 156 |
Page 157 |
Page 158 |
Page 159 |
Page 160 |
Page 161 |
Page 162 |
Page 163 |
Page 164 |
Page 165 |
Page 166 |
Page 167 |
Page 168 |
Page 169 |
Page 170 |
Page 171 |
Page 172 |
Page 173 |
Page 174 |
Page 175 |
Page 176 |
Page 177 |
Page 178 |
Page 179 |
Page 180 |
Page 181 |
Page 182 |
Page 183 |
Page 184 |
Page 185 |
Page 186 |
Page 187 |
Page 188 |
Page 189 |
Page 190 |
Page 191 |
Page 192 |
Page 193 |
Page 194 |
Page 195 |
Page 196 |
Page 197 |
Page 198 |
Page 199 |
Page 200 |
Page 201 |
Page 202 |
Page 203 |
Page 204 |
Page 205 |
Page 206 |
Page 207 |
Page 208 |
Page 209 |
Page 210 |
Page 211 |
Page 212 |
Page 213 |
Page 214 |
Page 215 |
Page 216 |
Page 217 |
Page 218 |
Page 219 |
Page 220 |
Page 221 |
Page 222 |
Page 223 |
Page 224 |
Page 225 |
Page 226 |
Page 227 |
Page 228 |
Page 229 |
Page 230 |
Page 231 |
Page 232
