The shelf‐like protuberance on the outer side of the pit in polygnathid conodonts is a unique and easily recognizable feature usually viewed as taxonomically significant for the biostratigraphically important species Polygnathus serotinus. However, the protuberance is also developed in other late Emsian‐early Eifelian polygnathids, which mainly include P. praeinversus, P. vigirei, P. pseudoserotinus and P. linguiformis bultyncki. Although several evolutionary lineages have been proposed to elucidate the phylogenesis of the protuberance, its morphogenesis has been rarely studied. In this study, intraspecific variation of P. linguiformis bultyncki is investigated on the basis of abundant specimens from South China and Germany, and two morphotypes are recognized. Moreover, three morphogenetic patterns of the shelf‐like protuberance are proposed. Polygnathus praeinversus and P. pseudoserotinus are assigned to the first morphogenetic pattern, with the protuberance formed as a vestigial outer flank of the asymmetrical basal cavity. The second pattern, which can be applied to P. serotinus and P. vigirei, is characterized by a protuberance that is formed as a shelf‐like extension of the pit partially buttressed by platform material in juvenile/immature specimens, and by a well‐developed shelf‐like extension of the pit on its inner side and a bulge in the platform proper on its outer side in mature specimens. Polygnathus linguiformis bultyncki is characterized by the third morphogenetic pattern. Its protuberance is ontogenetically acquired and though absent in juvenile specimens, in immature and mature specimens it is formed as a bulge in the platform proper fully supported by platform material. This study provides an exemplar for conodont research of other geological periods as growth histology can play an important role in investigating morphological variation of conodonts.

中文翻译：

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早于艾美时期的伊菲尔早期伊菲尔多生的牙形牙形体的架子状隆突的形态形成模式

gna虫牙形牙坑深处的架子状突起是一个独特且易于识别的特征，通常被认为对生物地层学上重要的Poly虫牙菌具有重要的分类学意义。但是，突起也研发出其他后期埃姆斯早期艾菲尔polygnathids，其中主要包括P. praeinversus，P. vigirei，P. pseudoserotinus和P. linguiformis bultyncki。尽管已经提出了几种进化谱系来阐明突起的系统发育，但是很少研究其形态发生。在这项研究中，P。linguiformis bultyncki种内变异在华南和德国丰富的标本的基础上进行了研究，发现了两种形态型。此外，提出了架子状隆起的三种形态发生模式。gna蚕和假浆膜假单胞菌被分配到第一个形态发生模式，突起形成为不对称基底腔的残留外侧面。第二种模式，可以应用于P. serotinus和P. vigirei的特征是，突出物形成为凹坑的架子状延伸，在少年/未成熟标本中部分被平台材料支撑，而凹坑在其内侧形成了成熟的架子状延伸，并在内部凸出。在成熟标本中，平台应位于其外侧。舌叶虎舌草的特征是第三种形态发生模式。它的隆起是个体发育获得的，尽管在少年标本中不存在，但在未成熟和成熟的标本中，它在适当地完全由平台材料支撑的平台中形成为凸起。这项研究为其他地质时期的牙形石研究提供了一个范例，因为生长组织学可以在研究牙形石的形态变化中发挥重要作用。