分类: 生物学 >> 生物进化论 提交时间: 2024-03-21
摘要: The affinity of ‘Dongfangaspis qujingensis’, initially assigned to Dongfangaspisbut later to Laxaspis, has long been controversial. However, the taxonomical revision raisesa new problem of junior homonym since the type species of Laxaspis is L. qujingensis. Here,we describe some new materials of ‘Dongfangaspis qujingensis’ and Damaspis vartus fromthe Xishancun Formation (early Lochkovian, Early Devonian) in Qujing, Yunnan Province.‘Dongfangaspis qujingensis’ strikingly resembles Damaspis vartus in the slightly longerheadshield, bifurcated ends of the lateral transverse canals, unconnected V-shaped posteriorsupraorbital canals, and at least seven pairs of lateral transverse canals issuing from the lateraldorsal canal. These similarities indicate that ‘D. qujingensis’ is more suggestive of Damaspis thanDongfangaspis and Laxaspis. Therefore, we propose to remove ‘Dongfangaspis qujingensis’ fromLaxaspis to Damaspis. The new specimens of Damaspis vartus reveal five long lateral transversecanals on the right side, corroborating that the asymmetric sensory canal system in the holotype isthe intraspecific variation.
分类: 生物学 >> 动物学 提交时间: 2023-07-12 合作期刊: 《古脊椎动物学报》
摘要: The Shuitangba subbasin lignite deposits of the Zhaotong Basin in northern Yunnan Province have produced vertebrate fossils of terminal Miocene age. We conducted test wet screening of fossiliferous sediment in 2014 to increase representation of small mammals. This effort produced four teeth of a very large bamboo rat, much larger than the previously known bamboo rat present at Shuitangba, and representing a new species. This new species is characterized by its molars being remarkably larger than those of other known species of Miorhizomys, and being hypsodont with cementum, and less anterorposteriorly compressed. The age of this new species from Shuitangba is in the range of 6.2 to 6.7 Ma. It appears that diverse bamboo rats of the extinct genus Miorhizomys were present in the Late Miocene of Yunnan, somewhat before the 6 Ma appearance of extant Rhizomys to the north in the vicinity of Shanxi Province.
分类: 生物学 >> 动物学 提交时间: 2022-04-16 合作期刊: 《古脊椎动物学报》
摘要: A new genus and species of the family Eugaleaspidae (Eugaleaspiformes, Galeaspida), Xitunaspis magnus gen. et sp. nov., is described from the Lower Devonian Xitun Formation in Qujing, Yunnan Province, China. The new genus displays the diagnostic characters of the Eugaleaspidae, including a slit-like median dorsal opening, no inner cornual process, developed median dorsal canals, and only three pairs of lateral transverse canals extending from lateral dorsal canals. Different from the other eugaleaspids, X. magnus possesses a large headshield with thick dermal bone and a more plesiomorphic sensory canal system. The phylogenetic analysis of the Galeaspida reveals that Xitunaspis clusters with Dunyu and Eugaleaspis to form a monophyletic clade Eugaleaspidae Liu, 1965, and has a closer relationship with Dunyu than Eugaleaspis by sharing the thick dermal bone of the headshield. The new finding represents the first convincing fossil record of the Eugaleaspiformes in the middle Lochkovian Xitun Formation and adds to our knowledge about the morphology of eugaleaspiforms and the evolutionary pattern of the sensory canal system in the Eugaleaspiformes and even Galeaspida.
分类: 生物学 >> 动物学 提交时间: 2020-09-15 合作期刊: 《古脊椎动物学报》
摘要: Neogene strata rich in fossil mammals are well exposed in central Nei Mongol, China. Over a dozen mammalian faunas in chronological succession from Early Miocene to Early Pliocene were discerned in this region, and they built a fundamental part of the Neogene land mammal biochronological system in northern China. Tuchengzi was first recognized for producing abundant mammalian fossils during the Sino-Soviet Paleontological Expedition (SSPE) initiated in 1959. However, all unearthed fossils from the SSPE were either large- or middle-sized mammals, and small mammal fossils in the Tuchengzi Fauna were deficient for a long time. The composition and biochronological position of the Tuchengzi Fauna in the Neogene mammalian biochronological system in northern China was not particularly clear. The new fossils here reported are represented by 6 taxa of small mammals. Based on the co-occurrence of Lophocricetus grabaui, Sinocricetus zdanskyi, Prosiphneus licenti, Hansdebruijnia pusilla, and Moschus grandaevus, the age of the Tuchengzi Fauna is constrained to late Late Miocene or Baodean Chinese Land Mammal Age, slighter younger than the Baogeda Ula Fauna and older than the Ertemte Fauna. Judging from the fossil composition, the Tuchengzi Fauna possibly inhabited a forest-steppe mixed habitat during the late Late Miocene.
分类: 生物学 >> 动物学 提交时间: 2019-06-17 合作期刊: 《古脊椎动物学报》
摘要: We reconstructed a wealth of three-dimensional virtual models of vertebrate microremains from the Xitun Formation and lower part of the Xishancun Formation (Lochkovian,Lower Devonian) of Qujing, Yunnan by means of high-resolution computed tomography. One genus (Parathelodus) and seven species (P. trilobatus, P. asiaticus, P. cornuformis, P. scitulus, P. xitunensis sp. nov., P. wangi sp. nov. and P. liaokuoensis sp. nov.) of thelodonts are described. The new discovery extends the stratigraphic distribution of Parathelodus from the Xitun Formation and the upper part of the Xishancun Formation to the lower part of the Xishancun Formation, the horizon close to the Silurian-Devonian boundary. The three new species, P. xitunensis, P. wangi and P. liaokuoensis, enhance our knowledge of the thelodont diversity from the Early Devonian of China.