Table of Content

15 December 2012, Volume 50 Issue 4

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THE MICROVERTEBRATE REMAINS AND ASSEMBLAGE SEQUENCES ACROSS THE SILURIAN/DEVONIAN TRANSITION IN WEST QINLING, CHINA

ZHAO Wen-Jin, WANG Nian-Zhong, ZHU Min, JIA Lian-Tao

2012, 50(4):  309-321. 

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West Qinling is an important area for the study of the Silurian/Devonian Boundary (SDB) in the South China Block. The SDB sequence in the Putonggou Section includes the upper part of the Yanglugou Formation and the lower part of theXiaputonggou Formation, in which microvertebrate remains (thelodonts, placoderms, acanthodians and chondrichthyans) in association with conodonts and brachiopodshave been collected. Two microvertebrate assemblages are recognized in the Putonggou Section: the Yanglugou Assemblage from the upper part of the Yanglugou Formation, and the Xiaputonggou Assemblage from the lower part of theXiaputonggou Formation in association with the conodont Icriodus woschmidti woschmidti. The Yanglugou Assemblage yields the acanthodians Gomphonchus sandelensis and Ischnacanthidae gen. indet., and the Xiaputonggou Assemblage includes the thelodonts (Parathelodus scitulus, P. asiaticus and P. cornuformis), the acanthodians (Nostolepis gracilis, N. striata, N. tewonensis, Gansuichthys liui,Poracanthodes zoigenensis, Poracanthodes cf. P. porosus, Ischnacanthys sp.), thechondrichthyan (Arauzia ? sp.), and the placoderm (a pectoral fin fragment ofChuchinolepis ? sp.). Based on the correlation with the microvertebrate biozones in East Baltic, the Yanglugou and Xiaputonggou assemblages are referred to the late Pridoli and the early Lochkovian respectively, thus providing paleoichthyological evidence for the location of the SDB in West Qinling.

A NEW SPECIES OF SINAMIA FROM WESTERN LIAONING,CHINA

ZHANG Jiang-Yong

2012, 50(4):  322-334. 

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A new species of sinamiid fish, Sinamia liaoningensis, is described from the Barremian-Aptian Yixian and Jiufotang formations of western Liaoning, China and the morphology of the sinamiid fishes is reviewed. The new materials reveal three synapomorphies of the Sinamiidae proposed by Grande and Bemis (1998): the presence of only a single median parietal; three pairs of extrascapular bones; and short dermopterotic about equal in length to parietal length. The new species was attributed to Sinamia because it has three synapomorphies of the genus: relative small postinfraorbitals, a long dorsal fin and rhombic scales. The new species is a big podgy fish and it differs from all other species of the genus in the shape of the rostral, nasal, preopercle, the size and shape of infraorbitals, more subinfraorbitals (3), less dorsal fin rays (18), more caudal fin rays (16), more scale rows (32) between the origin of the anal fin and the dorsal margin of the body, and lack of serrated scales. The anterior half of the caudal fin rays of S. liaoningensis sp. nov. has remains of thin fibrous actinotrichia.

New remains of Canis chihliensis (Mammalia, Carnivora) from Shanshenmiaozui, a Lower Pleistocene site in Yangyuan, Hebei

TONG Hao-wen, HU Nan, WANG Xiao-ming

2012, 50(4):  335-360. 

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 From 2006？2011, numerous Canis specimens were recovered from the newly discovered Shanshenmiaozui Locality in the Nihewan Basin. The material includes broken crania, premaxillae, maxillae, mandibles and postcranial skeleton with most of the elements preserved, and represents the most extensive and informative sample of early fossil Canis ever recovered in China. This material can be assigned to the species Canis chihliensis based on morphological and metric characters, including large size, robust I3, elongated P4 with anterior notch and well-developed protocone, M1 strongly mesiodistally compressed and with broad cingular hypocone, m1 with metaconid and entoconid (however small), M2 and m2 large relative to M1 and m1 respectively, and m2 with broad talonid. Measurements of the skulls and the teeth are similar to the equivalent measurements for Canis lupus, but those of the postcranial elements are smaller. Canis chihliensis is characterized by reduction of the lingual cuspids on the lower molars, an elongated P4, and a mesiodistally compressed M1. However, the first lower molars from Shanshenmiaozui are quite variable in the development of their lingual cuspids. This study shows that it is not easy to distinguish Canis chihliensis fromXenocyon dubius (=Cuon dubius) based exclusively on characters of the first lower molar, and the taxonomic status of the latter species is still open to question. Both of them differ greatly in morphology from the African hunting dog Lycaon pictus. Unlike in Canis chihliensis, the tooth dimensions of Xenocyon dubius are quite variable. The fossil bearing stratum at Shanshenmiaozui can be correlated with, but probably later than that at the neighboring Xiaochangliang Site, which has an age of ca. 1.36 Ma.

APPLYING GEOMETRIC MORPHOMETRICS TO THE CLASSIFICATION AND IDENTIFICATION OF SMALL MAMMALS − A Case Study of Large Samples of Four Arvicoline Species

ZHANG Ying-Qi, YAN Ya-Ling, LIU Yi-Hong, WEI Guang-Biao

2012, 50(4):  361-372. 

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Small mammals play a very important role in late Cenozoic biostratigraphy and biochronology. Especially since screen-washing technology began to be applied in paleontological investigations, it has often been possible to acquire large samples of small mammal fossils, which makes them a more effective proxy for biostratigraphy and biochronology than large mammals. Accordingly, classification and identification of these large samples have become a fundamental paleontological task. However, when dealing with them using empirical or intuitive traditional morphological methods, it is impossible to avoid paying too much attention to some slight and inconsistent differences and “oversplitting” taxonomic units, or conversely neglecting some consistent differences that are imperceptible to human eyes and lumping several taxonomic units together. In either case, subjective factors will introduce a degree of arbitrariness into the classification and identification of the specimens. To avoid this, a quantitative geometric morphometric method of classification and identification based on analysis of large samples is explored in this paper. The subjects of this case study are 1284 isolated molars of Mimomys gansunicus, Heteromimomys zhengi and Villanyia fanchangensis from the lower Lower Pleistocene Renzidong site, and 163 specimens ofMimomys bilikeensis from the Lower Pliocene Bilike site are used as a point of reference. 7-14 2D homologous landmarks were defined on the occlusal surface of each of the six molars and used as the basis for a linear discriminant analysis. The results confirm that there are three different arvicoline species in the Renzidong sample, and the linear discriminant functions produced in the analysis can describe the consistent differences that exist among the species in this large sample. Furthermore, the same functions can be used as a basis for identifying newly recovered fossil specimens of related arvicoline species. Because geometric morphometrics can deal with both discrete landmark data and continuous outline data pertaining to significant morphological characters, and is suitable for use in both 2D and 3D, this method can be generally applied to the classification and identification of small mammal fossils.

THE HORIZON OF DASHANKOU FAUNA AND THE PERMO-TRIASSIC STRATA IN NORTHERN QILIAN AREA, CHINA

Yumen, Gansu; Permo-Triassic; Xidagou, Qingtoushan and Sunan formations

2012, 50(4):  373-381. 

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After reexamining the horizon producing the Dashankou Fauna and the division of Permo-Triassic strata in northern Qianlian area, China, we found the misuse of the name “Xidagou Formation”. Xidagou is held as group name for lower-middle Triassic of northern Qilian area, and cannot apply to other strata. We suggest rename former Xidagou Formation with Dashankou Fauna as Qingtoushan Formation and design the Qingtoushan section as the holostratotype; and the former Xidagou Formation applied to upper Triassic should be renamed.