Table of Content

15 June 2018, Volume 56 Issue 2

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Synchrotron X-ray tomographic microscopy reveals histology and internal structure of Galeaspida (Agnatha)

GAI Zhi-Kun 

2018, 56(2):  93-105. 

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Synchrotron Radiation X-ray Tomographic Microscopy (SRXTM) is a powerful non-destructive method in paleontology, providing ultra-high-resolution 3D insights into the internal structure of fossils.Employing SRXTM, the skull specimens of Shuyu zhejiangensis, a 428 million-year-old galeaspid from the Silurian of Changxing, Zhejiang Province, are investigated. The subsequent analyses indicate that the endoskeletalskull of S. zhejiangensis is composed wholly of cartilage without convincing evidence for the presence of perichondral bone. The cranial anatomy of S. zhejiangensis are unusually preserved in three dimensions largely due to the non-random decay of the cartilaginous braincase and its connecting ‘soft’ tissues. Using Amira or Avizosoftware, seven virtual 3D endocasts of the skull of S. zhejiangensis were created revealing the gross internal cranial anatomy of galeaspids in great detail for the first time. The preliminary results indicate that during evolution the galeaspid head experienced a fundamental reorganization resulting in the development of jaws. 

A large peltopleurid fish (Actinopterygii: Peltopleuriformes) from the Middle Triassic of Yunnan and Guizhou, China

XU Guang-Hui, MA Xin-Ying, ZHAO Li-Jun

2018, 56(2):  106-120. 

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Peltopleuriformes are a stem group of neopterygian fishes from the Middle–Late Triassic marine ecosystems in Europe and South China, including the Peltopleuridae and Thoracopteridae. Among them, peltopleurids are commonly small-sized fishes with a standard length (SL) rarely exceeding 55 mm. Here, a new peltopleurid, Peltopleurus tyrannos sp. nov., is described based on three well-preserved specimens from the Middle Triassic (Ladinian) of Fuyuan, Yunnan and Xingyi, Guizhou, China. The discovery documents the largest species (SL = 72 mm) of this genus in the Middle Triassic and provides new insights into the morphologic and trophic diversifications of peltopleurids. In addition to large conical teeth on the oral margins of the jaws, the newpeltopleurid bears many blunt teeth of various sizes on the oral margin of the palatopterygoid, which may be used for crushing some hard-shelled invertebrates (e.g., crustaceans) or small armored fishes. By contrast, the more commonly founded relative, P. orientalis, from the same ecosystem (Xingyi Biota) is toothless and has a much smaller body size (SL=26 mm), and probably represents a schooling fish that fed on small planktonic invertebrates. The new finding shows that Peltopleurus from the late Middle Triassic Xingyi Biota of South China had evolved into two different ecomorphotypes.   

Restudy of Regalerpeton weichangensis (Amphibia: Urodela) from the Lower Cretaceous of Hebei, China

RONG Yu-Fen

2018, 56(2):  121-136. 

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Regalerpeton weichangensis was established in 2009 on an incomplete skeleton preserved mainly as an impression from the Lower Cretaceous of Hebei, China. However, several anatomical characters were misinterpreted due to distortion of the holotype, and its taxonomic position has been in debate. In this paper, R. weichangensis is redescribed based on eight new specimens and its diagnosis and phylogenetic position are re-examined. This work shows that R. weichangensis was a neotenic form with ossified carpals and tarsals. It has a series of unique combination of characteristics including the vomer with a transverse vomerine tooth row, anterior end of the cultriform process of the parasphenoid indented, basibranchial II triradiate, a long tail exceeded the snout-pelvis length and scapulocoracoid with a rectangular coracoid end. Phylogenetic analysis suggests Regalerpeton, Jeholotriton and Pangerpeton should be placed in the suborder Salamandroidea with three synapomorphies. Moreover, they also share unicapitate ribs with Cryptobranchoidea, which indicates that they represent an important stage of evolution in the Cryptobranchoidea-Salamandroidea split.

Taxonomic reassessment and phylogenetic test of Asiatosuchus nanlingensisYoung, 1964 and Eoalligator chunyii Young, 1964

WU Xiao-Chun, LI Chun, WANG Yan-Yin

2018, 56(2):  137-146. 

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The present paper revalidated Asiatosuchus nanlingensis Young, 1964 and Eoalligator chunyii Young,1964 in taxonomy based on a detailed comparative study on those relevant specimens. New information derived from this study revealed that A. nanlingensis and E. chunyii were truly distinguishable from each other and therefore, diagnosis was further revised for each of them. A. nanlingensis is large, with a moderately long or a very elongate snout, and characterised mainly by the combination of the following characters such as: the quadrate with a lateral condyle much larger than the medial one, the surangular pinched off before reaching the end of the retroarticular process, the dental margins (at least the posterior portion) of the jaws nearly straight, and the presence of a fossa/sulcus on the lateral surface of the surangular lateral to the mandibular fossa. E. chunyii is a median-sized, short-snouted animal and characterised mainly by the combination of the following characters such as: the condyles of the quadrate similar in size, the dental margins of the jaws strongly concavo-convex, the dentary symphyses very short, the splenial not entering the mandibular symphysis, and the presence of a fossa/sulcus on the lateral surface of the surangular lateral to the mandibular fossa. With new information derived from this study, the phylogenetic relationships of A. nanlingensis and E. chunyii were tested, which did not support the view that the two species formed a monophyletic clade and opposed that E. chunyii could be considered as the synonym of A.nanlingensis. 

New materials of Cervidae (Artiodactyla, Mammalia) from Tuchengzi of Huade, Nei Mongol, North China

DONG Wei, LIU Wen-Hui, ZHANG Li-Min, CAI Bao-Quan

2018, 56(2):  157-175. 

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Five taxa of Cervidae were identified from the new collection at Tuchengzi locality in Huade, Nei Mongol: Eostyloceros blainvillei, E. triangularis, Euprox sp., Cervavitus huadeensis and C. shanxius, among which the first three taxa were discovered for the first time in Huade area, and the dental specimens of the last two taxa from Tuchengzi locality are also described for the first time. E. blainvillei is a large muntiacine, diagnosed by long, thick and medially curved main beam and a relatively long brow tine emerging directly from the burr. It was originally found in Yushe Basin in Shanxi Province, and reported later from Qaidam Basin in Qinghai Province. Huade is the third area yielding the species. E. triangularis distinguishes from E. blainvillei by its special main beam with triangular cross sections, and it was reported only from Yushe Basin. Its presence in Huade extended its geographic distribution northward to Nei Mongol. Euprox is a transitional form of cervids from permanent antlers to seasonally deciduous ones and it is found in several localities across Eurasia. Huade is the third area in Nei Mongol yielding the taxon after Tung Gur and Siziwang Qi (Siziwang Banner). C. huadeensis is a pliocervine with four tines, and particularly with two distal tines sword-like. It is found at Tuchengzi for the second time, but not elsewhere so far, and it seems to be an endemic taxon. C. shanxius distinguishes from C. novorossiae by absence ofPalaeomeryx fold on lower molars. It is widely found in Shanxi, Shaanxi, Gansu and Nei Mongol of northern China. It is often found with numerous specimens in a locality that indicates it lived in large herds. E. blainvillei,E. triangularis and C. shanxius are main members of Yushe I, i.e. Mahui Formation or Baodean. Euprox appeared also mainly in the Late Miocene. The geological age of Tuchengzi locality based on excavated cervids is therefore the Late Miocene. The numerous specimens of C. shanxius indicates forested environment in Huade area in that age.