The Bogda Mountains of northeastern Xinjiang Province, China, preserve a Permian-Triassic sequence which has produced a broad range of terrestrial Vertebrates, including non-Mammalian Therapsids such as Dicynodonts, Gorgonopsians, and Therocephalians. Two Therocephalians have been described from this sequence to date, Urumchia lii from the Early Triassic Jiucaiyuan Formation, and Dalongkoua fuae from the Late Permian Guodikeng Formation, although several other species are known from elsewhere in North China, including Shiguignathus wangi, Jiufengia jiai, Euchambersia liuyudongi, and Caodeyao liuyufengi from the Late Permian Naobaogou Formation of Inner Mongolia, Moschowhaitsia lidaqingi from the Late Permian Wufoshi Formation of Gansu Province, Hazhenia concava from the Early Triassic Heshanggou Formation of Inner Mongolia, Ordosiodon lincheyuensis, Ordosiodon youngi and Nothogomphodon sanjiaoensis from the Early Triassic Ermaying Formation of Shanxi Province, Yikezhaogia megafenestrala. from the Early Triassic Ermaying Formation of Inner Mongolia, and Traversodontoides wangwuensis from the Middle Tirassic Ermaying Formation of Henan Province.
In a paper published in the journal Vertebrata PalAsiatica on 20 July 2024, Lui Jun of the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences and the College of Earth and Planetary Sciences of the University of the Chinese Academy of Sciences, and Fernando Abdala of the Área de Paleontología at Unidad Ejecutora Lillo and the Evolutionary Studies Institute at the University of the Witwatersrand, describe a new species of Baurioid Therocephalian from the Early Triassic Jiucaiyuan Formation of Jimsar County in Xinjiang Province, China.
The new species is described from a slab on which a partial snout and several postcranial skeletal elements were visible on the surface. When X-ray microcomputed tomography was applied to this slab it was discovered that two largely disarticulated partial skeletons were present within. The partial skeleton is designated as the holotype of the new species (in taxonomy, a specimen is named as the holotype when an new species is discovered, and any other specimens are deemed to belong to that specie species if the can be shown to belong to the same species as the holotype), which is given the name Jiucaiyuangnathus confusus, where 'Jiucaiyuangnathus' means 'Jiucaiyuan-jaw', in reference to the Jiucaiyuan Formation, and 'confusus' means 'confusing' in reference to the difficulty had deciphering the specimens. It is thought that the snout is derived from one of the post-cranial skeletons, but it is impossible to tell which.
Jiucaiyuangnathus confusus (IVPP V32945, holotype) from Jimsar, Xinjiang. (A)–(C) photo (A) and 3D rendering (B) of the left side of the snout in lateral and 3D rendering of the medial view of the left side of the snout (C); (D). 3D rendering of the snout in posterior view showing the bones as preserved. Abbreviations: afo. anteriormost foramen; cc. christa choanalis; F. frontal; L. lacrimal; l.c. lacrimal canal; M. maxilla; m. maxillary tooth; m.a. maxillary antrum; msf. maxillo-septomaxillary foramen; pdl. dorsal layer of palatine; pit. maxillary round pit; PL. palatine; PM. premaxilla; pml. medial layer of palatine; sH, sinus Highmore; SM. septomaxilla; V. vomer. Lui & Abdala (2024).
The preserved portion of the jaws has five surviving incisors and lacks canines. There is a diastema (gap) between the last incisor in the upper jaw and the first maxillary tooth, but no equivalent gap is present in the dentition of the lower jaw, traits consistent with Jiucaiyuangnathus confusus being a Baurioid Therocephalian.
3D rendering of Jiucaiyuangnathus confusus (IVPP V32945, holotype) from Jimsar, Xinjiang . (A) The preserved snout in ventral view; (B), (C) vomer in dorsal (B) and ventral (C) views, vomer is reconstructed in the natural position in (C); (D) left dentary in lateral view; (E), (F) mandibles in dorsal (E) and ventral (F) views. Abbreviations: 1st ic. first incisor; ch. choana; D. dentary; d. dentary tooth; F. frontal; for vn. place for vomeronasal organ; M. maxilla; N. nasal; PL. palatine; PM. premaxilla; SP. splenial; V. vomer; v.f. vomerine foramen. Lui & Abdala (2024).
The two partial skeletons are given the designations IVPP V32946-1 (which is marginally the smaller of the two) and IVPP V32946-2 (which is marginally the larger). While both are largely disarticulated, most of the bones are close to their original positions, making it possible to assign them to one of the two skeletons wirh confidence. In both skeletons, the neural arches are separate from the centra of the vertebrae, making it likely that they were juveniles at the time of death.
Posterior skeletons of Jiucaiyuangnathus confusus (IVPP V32946) from Jimsar, Xinjiang (A), (B) photo of the slab; (C), (D) 3D rendering of bones. Gray (IVPP V32946-1) and light purple (IVPP V32946-2) are bones of each specimen. Light blue uncertain. Lui & Abdala (2024).
Specimen IVPP V32946-1 has ten presacral vertebrae preserved, the the atlas and axis, five thoracics, and three lumbars, as well as three sacral vertebrae and a series of at least 11 caudal vertebrae, five of them being rod-like. There are three short, curved cervical vertebrae, and five incomplete ribs on the left side and seven nearly complete ribs on the right side of the thoracic vertebrae. An almost complete pelvic girdle lacks only the left ischium. A right femur, lacking a proximal end and with an incomplete distal end, probably belongs to this skeleton.
3D rendering of Jiucaiyuangnathus confusus (IVPP V32946-1) from Jimsar, Xinjiang. (A), (B) The preserved skeleton in dorsal (A) and ventral (B) views; (C) right femur in distal view; (D)–(F) atlas and axis in anterior (D), left (E), and right (F) lateral views; (G) four thoracic vertebrae in right lateral view; (H), (I) sacral region in lateral (H) and dorsal (I) views; (J) caudal vertebrae Abbreviations: aic. atlas intercentrum; cdr. caudal rib; cdv. caudal vertebra; cr. cervical rib; FE. femur; lv. lumbar vertebra; ns. neural spine; sr. sacral rib; sv. sacral vertebra; tp. transverse process; tr. thoracic rib; tv. thoracic vertebra. Lui & Abdala (2024).
Specimen IVPP V32946-2 has ten continuous vertebrae, interpreted as thoracics, as well as 13 complete long left thoracic ribs and the proximal side of eight right thoracic ribs. The head of the first sacral rib is considerably expanded dorsoventrally with a short, stout shaft curving ventrally and a very expanded distal end to contact the ilium. This specimen has a nearly complete left scapula and the dorsal portion of the right scapula, as well as a separated procoracoid, which lies close to the ventral side of the scapula. An incomplete interclavicle appears as a broad flat bone that gently curves ventrally, and the sternum is preserved as a large, thin, longer than wide flat plate. Again, the pelvic girdle is almost complete, in this case lacking the left pubis. The proximal parts of both femurs are preserved, with the right being more complete.
3D rendering of Jiucaiyuangnathus confusus (IVPP V32946-2) from Jimsar, Xinjiang. (A), (B) Skeleton in dorsal (A) and ventral (B) views; (C) part of thoracic vertebrae in left lateral view; (D) two sacral and three anterior caudal ribs; (E)–(H) sacral ribs of (D) in dorsal (E), (G) and ventral (F), (H) views; (I)–(L) two smaller sacral ribs in dorsal (I), (K) and ventral (J), (L) views Abbreviations: cdr. caudal rib; mt. metatarsal; sr. sacral rib. Liu & Abdala (2024).
Neither of the skeletons has neural arches fused to the centra, suggesting that they were both juveniles when they died, but the neural arches of the smaller skeleton are more distant from the centra than in the larger, possibly suggesting that it was younger and less developed. There are also differing degrees of ossification in the bones of the pelvic girdle of the two skeletons, which again suggest different levels of development.
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