Research Center of Natural History and Culture, Qujing Normal University, Qujing, Yunnan Province, China.
Key CAS Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, China.
PLoS One. 2020 Feb 13;15(2):e0228589. doi: 10.1371/journal.pone.0228589. eCollection 2020.
The Sinacanthida ordo nov. and Mongolepidida are spine- and scale-based taxa whose remains encompass some of the earliest reported fossils of chondrichthyan fish. Investigation of fragmentary material from the Early Silurian Tataertag and Ymogantau Formations of the Tarim Basin (Xinjiang Uygur Autonomous Region, China) has revealed a diverse mongolepidid and sinacanthid fauna dominated by mongolepids and sinacanthids in association with abundant dermoskeletal elements of the endemic 'armoured' agnathans known as galeaspids. Micro-computed tomography, scanning electron microscopy and histological sections were used to identify seven mongolepid genera (including Tielikewatielepis sinensis gen. et sp. nov., Xiaohaizilepis liui gen. et sp. nov. and Taklamakanolepis asiaticus gen. et sp. nov.) together with a new chondrichthyan (Yuanolepis bachunensis gen. et sp. nov.) with scale crowns consisting of a mongolepid-type atubular dentine (lamellin). Unlike the more elaborate crown architecture of mongolepids, Yuanolepis gen. nov. exhibits a single row of crown elements consistent with the condition reported in stem chondrichthyans from the Lower Devonian (e.g. in Seretolepis, Parexus). The results corroborate previous work by recognising lamellin as the main component of sinacanthid spines and point to corresponding developmental patterns shared across the dermal skeleton of taxa with lamellin and more derived chondrichthyans (e.g. Doliodus, Kathemacanthus, Seretolepis and Parexus). The Tarim mongolepid fauna is inclusive of coeval taxa from the South China Block and accounts for over two-thirds of the species currently attributed to Mongolepidida. This demonstrates considerable overlap between the Tarim and South China components of the Lower Silurian Zhangjiajie Vertebrate Fauna.
新的Sinacanthida 目和 Mongolepidida 是脊椎和鳞片为基础的分类单元，其遗骸包括一些最早报道的软骨鱼类化石。对塔里木盆地早志留世塔塔尔特塔和伊莫甘陶组（中国新疆维吾尔自治区）的零碎材料的研究揭示了一个多样化的 Mongolepidida 和 Sinacanthida 动物群，以 Mongolepids 和 Sinacanthids 为主，与特有的“装甲”无颌鱼的丰富真皮骨骼元素密切相关，这些无颌鱼被称为 Galeaspids。微计算机断层扫描、扫描电子显微镜和组织切片用于鉴定七个 Mongolepid 属（包括中华新似盔甲鱼属和小海口鱼属的两个新种以及亚洲似盔甲鱼属和新种）以及一种新的软骨鱼类（八臂三翼鱼属和新种），其鳞片冠由 Mongolepid 型无管牙本质（层状蛋白）组成。与 Mongolepids 更复杂的冠结构不同，八臂三翼鱼属 nov. 表现出单一排冠元素，与下泥盆世（例如，在 Seretolepis 和 Parexus 中）报道的原始软骨鱼类的情况一致。研究结果证实了之前的工作，即认定层状蛋白是 Sinacanthid 刺的主要成分，并指出了在具有层状蛋白和更衍生的软骨鱼类（例如 Doliodus、Kathemacanthus、Seretolepis 和 Parexus）的真皮骨骼中共享的相应发育模式。塔里木 Mongolepid 动物群包括华南板块同期的分类单元，占目前归因于 Mongolepidida 的物种的三分之二以上。这表明塔里木和华南早志留世张家界脊椎动物群之间存在相当大的重叠。
