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  • A taxonomical revision of ’Dongfangaspis qujingensis’from the Lower Devonian of Qujing, Yunnan Province

    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.

  • Reappraisal of Bothriolepis sinensis Chi, 1940 from the Tiaomachien Formation, Hunan, China

    分类: 生物学 >> 生物学其他学科 提交时间: 2023-09-05 合作期刊: 《古脊椎动物学报》

    摘要: 计荣森先生于1940年基于湖南长沙附近中泥盆统跳马涧组采集到的一些以前中背片 为代表的胴甲鱼类标本命名了中华沟鳞鱼(Bothriolepis sinensis), 这是在中国正式命名的第 一种古生代脊椎动物。虽然卢立伍于1988年对后续出产于模式种产地的其他中华沟鳞鱼材 料进行了补充描述,但研究者对中华沟鳞鱼的形态学特征和系统发育仍缺乏全面认识。在 此基于计荣森先生所采集的样本及一些收藏于中国地质博物馆未正式发表的化石,对中华 沟鳞鱼进行了再研究,补充了其头部与躯甲的部分特征。与其他沟鳞鱼类相比,中华沟鳞 鱼拥有以下一系列特征:较大的听上加厚区、颅顶甲长宽比1.41.6、较宽的眶窗(宽于颅顶 甲的1/3)以及扇形的眶前凹等。系统发育分析结果显示,B. askinae并非位于沟鳞鱼支系的 最原始位置;中华沟鳞鱼与广东沟鳞鱼因同样拥有纤细的附肢近端(长宽比大于7)而形成了 一个稳定的单系。本研究中绝大部分的中国种类均位于同一支系上,该支系的共有衍征为 其胸鳍感觉管从第一腹中片延伸至第二腹中片。此外,基于深骨平台数据的古生物地理 可视化分析结果表明,沟鳞鱼类最早于艾菲尔期出现在华南与东冈瓦纳,并迅速地辐射并 扩散至全球,最终于法门期在瑞亚克洋两岸表现出了高度的物种多样性。

  • The pelvic morphology of Parayunnanolepis (Placodermi, Antiarcha) revealed by tomographic data

    分类: 生物学 >> 动物学 提交时间: 2022-11-25 合作期刊: 《古脊椎动物学报》

    摘要: The pelvic morphology, and whether the pelvic fin is present or absent in the earliest jawed vertebrates are key in interpreting the origin of vertebrate paired fins. Parayunnanolepis xitunensis, an antiarch placoderm from the Early Devonian of Yunnan, South China, was previously described to possess the earliest evidence of both dermal and endoskeletal pelvic girdles, presumably for the attachment of the pelvic fins. Here, we redescribe the pelvic region of the holotype based on high-resolution computed tomographic data. Instead of having two large plates previously designated as dermal pelvic girdles, Parayunnanolepis possesses three pairs of lateral pelvic plates, and one large oval median pelvic plate. The paired pelvic plates are flat ventral plates, and differ from other dermal pelvic girdles in lacking a dorsal extension. There is no definitive evidence for the presence of an endoskeletal pelvic girdle in Parayunnanolepis, although the possibility cannot be ruled out. A comparison of the dermal pelvic plates in various jawed stem-gnathostomes suggests the presence of both paired and median pelvic plates is shared by different lineages and might be plesiomorphic. The jawed stem-gnathostomes may have recruited the ventral dermal skeleton of the post-thoracic body into different functional units.

  • Xitunaspis, a new eugaleaspid fish (Eugaleaspiformes, Galeaspida) from the Lower Devonian of Qujing, Yunnan

    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.

  • Redescription of Nochelaspis maeandrine, the largest eugaleaspiform from the Lower Devonian of Qujing, Yunnan

    分类: 生物学 >> 动物学 提交时间: 2021-07-30 合作期刊: 《古脊椎动物学报》

    摘要: The new specimens of the largest eugaleaspiform Nochelaspis maeandrine are redescribed from two localities of the Xishancun Formation in Qujing City, Yunnan Province, southwestern China. Nochelaspis is most suggestive of Yunnanogaleaspis from the same horizon, but differs in its slit-like median dorsal opening (length/width>6), much stronger inner cornual process, coarse stellate ornamentation, and the serrations along the edges of the median dorsal opening and headshield. The new findings reveal the morphological details on the ventral side of the headshield as well. The oralobranchial fenestra is covered by a large dermal ventral plate, which is decorated with dense, tiny granular tubercles, and aligned with six pairs of separated, large, and circular branchial openings. This condition is different from that of osteostracans, in which the oralobranchial fenestra is covered by numerous minute scales or larger dermal platelets, and the branchial openings are slit-shaped and covered by small skin flaps somewhat like those of elasmobranchs. However, the branchial openings of galeaspids and osteostracans are both located ventrally as in modern rays, indicating a benthic lifestyle dwelling on sandy or muddy substrates in a quiet marine environment.

  • New material of thelodonts from Lochkovian(Lower Devonian) of Qujing, Yunnan, China

    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.

  • The posterior cranial portion of the earliest known Tetrapodomorph Tungsenia paradoxa and the early evolution of tetrapodomorph endocrania

    分类: 生物学 >> 生物学其他学科 提交时间: 2018-12-04 合作期刊: 《古脊椎动物学报》

    摘要: Abstract Here the posterior cranial portion of the tetrapodomorph Tungsenia from the Lower Devonian (Pragian, ~409 million years ago) of Yunnan, southwest China, is reported for the first time. The pattern of posterior skull roof and the morphology of the otoccipital region of the neurocranium are described in detail, providing precious insight into the combination of cranial characters of the earliest known tetrapodomorph to date. The posterior cranium of Tungseniadisplays a mosaic of features previously linked either to basal dipnomorphs such as Youngolepis(e.g., the well-developed subjugular ridge, the strong adotic process, and the poorly developed fossa bridgei) or to typical tetrapodomorphs (e.g., the lateral dorsal aortae commenced from the median dorsal aorta postcranially). The independent ventral arcual plate is also found in the advanced tetrapodomorph Eusthenopteron. The new endocranial material of Tungsenia further fills in the morphological gap between Tetrapodomorpha (tetrapod lineage) and Dipnomorpha (lungfish lineage) and unveils the sequence of character acquisition during the initial diversification of the tetrapod lineage. The new phylogenetic analysis strongly supports the basalmost position of Tungsenia amongst the tetrapod lineage.

  • New findings of galeaspids (Agnatha) from the Lower Devonian of Qujing, Yunnan, China

    分类: 生物学 >> 动物学 提交时间: 2017-11-07 合作期刊: 《古脊椎动物学报》

    摘要: New findings of galeaspids (Agnatha) including Altigibbaspis huiqingae gen. et sp. nov., an indeterminate polybranchiaspid, Eugaleaspis changi, and Nanpanaspis microculus are described from the lower part of the Xishancun Formation (early Lochkovian, Early Devonian) near the northeast entrance of Liaokuo Park, Qujing City, Yunnan Province, China. The Polybranchiaspis-like new genus is characterized by a blade-like median dorsal ridge on the dorsal side of head-shield. The morphological disparity of the median dorsal ridge and spine in galeaspids suggests that these structures functioned more than providing a hydrodynamic stability. We assume that a high upright and compressed spine may render galeaspid fishes an apparently larger size as seen by a predator, and a blade-like median dorsal ridge may accomplish a defense against the claws of large sea scorpions. Nanpanaspis is peculiar in bearing two short laterally projecting processes on each side of the head-shield, and its phylogenetic relationship is discussed based on different interpretations on the homology of these processes. Considering the unique morphology of Nanpanaspis, and its early occurrence among the Huananaspiformes, we assign Nanpanaspis in the monogeneric family Nanpanaspidae to represent an early branch of the Huananaspiformes.