华南贵州宾夕法尼亚亚纪牙形类Neognathodus动物群:演化及地层对比意义

以华南斜坡相的罗甸纳庆剖面为代表,我国石炭纪宾夕法尼亚亚纪早–中期地层建立起了基于多个属种的牙形类分带,并可与全球其他地区同期地层进行广泛对比。Neognathodus属是这一时期一类常见的浅水相牙形类分子,在北美、东欧等地的浅水相地层中被广泛用作地层划分对比标志。该属分子在我国北方地区浅水相地层中是重要的带化石分子,而在华南斜坡相剖面中占比非常低。结合现有的生物地层框架,本文厘清了华南贵州罗甸附近3条斜坡相剖面中Neognathodus属分子的延限,尝试利用牙形类P1分子齿台的对称特征将其演化过程归纳为五个阶段,并提出阶段4中对称分子(如:N. bothrops, N. colombiensis, N. nataliae等)的再次出现可作为全球莫斯科阶底界的辅助对比标志。

The Pennsylvanian conodont genus Neognathodus from southern Guizhou, South China: evolution and its stratigraphic significance

Early to Middle Pennsylvanian conodonts from the Naqing section in Luodian, Guizhou, South China are well-documented. Based on several conodont genera from deep-water facies, their successions are applied as the standard conodont zonation from China for global correlation. Meanwhile, Neognathodus, a shallow-water genus that is rare in slope facies in South China, is of great importance in stratigraphic correlations especially in shallow-water facies in North America, East Europe, and North China. In this report, with reference to the standard zonation, successions of Neognathodus from three sections of slope facies (Naqing, Narao, and Luokun) in Luodian are studied and discussed. Furthermore, based mainly on the platform symmetry of the P₁ elements, an evolutionary trend divided into five stages is preliminarily introduced. The resurgence of symmetric elements of this genus in Stage 4 (e.g., N. bothrops, N. colombiensis, and N. nataliae) is suggested as an auxiliary index for the base of the global Moscovian Stage.