Li et al.—New Triassic diapsid from China
1309
Figure 3. Line drawing of the cervical series in the holotype of Pectodens zhenyuensis n. gen. n. sp., IVPP V18578. Abbreviations: cl = clavicle; cv = cervical vertebra; hy = hyoid; r = rib; sc = scapula.
facet for the rib in the first dorsal is pronounced, anteroposteriorly elongate (almost elliptical) and extends dorsally from a position low down on the centrum onto the neural arch. The articulation for the rib is broadest at themost postero-dorsal part of the process. The process is not as laterally elongate as in more-posterior dorsals. The rib associated with this vertebra is much longer than the preceding cervical rib, but it does have a small anterior “spur” on it. We therefore regard this as the first dorsal. Vertebra 15, and possibly also 13 and 14 (but they are covered),
there are at least six ribs forming a bundle alongside the ventrolateral aspect of the cervical vertebral column. The rib on the first preserved cervical (which has the anterior end covered by matrix) extends across two intervertebral joints. In the mid-region of the neck the anterior process of each rib is very prominent and extends anteriorly to partially overlap the preceding vertebra. This can be clearly seen in the third preserved vertebra. The neural spine remains low until vertebra eight. Adjacent to this vertebra there are eight rib shafts running parallel to each other, suggesting that the ribs from at least vertebra five extend back this far (three intervertebral joints). In the following vertebrae, there is a more pronounced, but still very elongate spine. The ribs on the third to last cervical extend across just one intervertebral joint. The ribs on the last two cervicals are short and extend barely beyond the length of the centrum. There are 11 definitive dorsals, and possibly asmany as 13. The
rib), but it is incomplete distally and it is probably a broken rib (Fig. 1). Vertebra 24 exhibits the anterior part of the centrum, but the rest is lost in the fracture between the two main blocks. Nevertheless, there are two rib shafts running into that fracture and these were most probably associated with vertebra 24. A rib adjacent to vertebra 22 is clearly flexed. The sacrals are difficult to determine as the fracture runs through
this part of the specimen. However, there would seem to be sufficient space to accommodate two sacrals, assuming that vertebra 27 is indeed the first caudal and that its transverse process did not contact the pelvis. The anterior caudals aremostly preserved in ventral view and it
has a very pronounced transverse process (probably at least 3mm long) (Fig. 1). It is narrow with a ventral ridge and depressions anteriorly and posteriorly where it attaches to the neural arch. There are no clear rib heads exposed, apart from the 12th one and possibly one lying just under the transverse process on 16. Therefore it cannot be said with certainty what form these took, but judging fromthe rather circular to ovoid ends to the transverse processes it can be assumed that they were holocephalous ribs with oval heads,which is consistent with the presumed head on rib 16. The mid-dorsal vertebral centra are somewhat elongate, at least they are similar in length to the most posterior cervical
vertebrae.Again itwould seemthat the transverse processes on all the dorsals are long and slender as in vertebra 15. Vertebra 23 has what appears to be a small anterior-projecting transverse process (parapophysis? – fused transverse process and
is therefore not possible tomake any comment on the nature of the neural spine. From caudal 10 onwards they have twisted over onto their side, and it is clear that the neural spine was anteroposteriorly elongate and low (Fig. 1). Anterior caudals bear long transverse processes (Table 3) and the facets for the chevron bones first appear on vertebra 29. The first chevron lies alongside vertebra 30 and is on its side so that the broad distal end is clearly exhibited. For the next four vertebrae, the chevrons have flipped and are visiblemore or less end on, but on vertebra 34 the chevron is again in fully articulated position and the distal end is seen to have an evenmore expanded form. On the next vertebra the chevron loses that shape and the anterior lamina/projection disappears altogether. It is also at this point that the transverse processes are lost. In some respects then, the caudal region is similar to Tanystropheus,as figured by Wild (1973, p. 67). The pectoral girdle and forelimb.—The scapula appears
dorsoventrally low and similar in overall form to the coracoid. One scapula seems to be lying on top of the other (Fig. 1). Both coracoids are displayed and the coracoid foramen is clear on the left side. The right coracoid is a little fragmented around the edges. Either one of the clavicles, or possibly a small exposure of the interclavicle, extends across the last cervical and towards the scapula. It is quite compressed, but nothing more can be said about this element. The humeri are long slender elements but with prominent
deltopectoral crests contributing to markedly expanded prox- imal heads. The distal ends of both humeri appear to be very narrow and expand little beyond the diameter of the shaft;
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 |
Page 233 |
Page 234 |
Page 235 |
Page 236 |
Page 237 |
Page 238 |
Page 239 |
Page 240 |
Page 241 |
Page 242 |
Page 243 |
Page 244 |
Page 245 |
Page 246 |
Page 247 |
Page 248 |
Page 249 |
Page 250 |
Page 251 |
Page 252 |
Page 253 |
Page 254 |
Page 255 |
Page 256 |
Page 257 |
Page 258 |
Page 259 |
Page 260 |
Page 261 |
Page 262 |
Page 263 |
Page 264 |
Page 265 |
Page 266 |
Page 267 |
Page 268 |
Page 269 |
Page 270 |
Page 271 |
Page 272 |
Page 273 |
Page 274 |
Page 275 |
Page 276
