Abstract An assemblage of Phlycticeras Hyatt from a precisely dated zone of Middle Callovian in Kutch, India has been analyzed. Systematic study reveals that this sample can be divided into two size groups. The larger set shows different adult modifications leading to ornamental polymorphism. Polymorphs are very similar, if not identical, to different chronospecies of Europe, which range between Middle to Upper Callovian. They are grouped under well-known Phlycticeras polygonium (Zieten). The group of smaller specimens on the other hand, strongly resembles a species, which has been previously described as Phlycticeras schaumburgi (Waagen) from the younger Upper Callovian horizons in Kutch. It has a peculiar ‘rooster’–like septicarinate keel in the venter near adult aperture. Phlycticeras-Oecoptychius have been considered as a possible dimorphic pair since long, but here shown to have many inconsistencies to support these views. Instead, sexual dimorphism is explored within Phlycticeras and P. polygonium-P. schaumburgi is proposed as possible antidimorphs. A similar association is found in different stratigraphic assemblages of Europe. Interestingly these two morphs show parallel evolutionary changes within the Phlycticeras genus.

中文翻译：

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印度 Kutch 的 Callovian Phlycticeras (Ammonoidea) 组合的性二态性和多态性

摘要 分析了来自印度卡奇的中卡洛维阶精确年代区的 Phlycticeras Hyatt 组合。系统研究表明，该样本可分为两个大小组。较大的集合显示导致观赏多态性的不同成虫修饰。多形体与欧洲的不同年代种非常相似，如果不完全相同，范围介于中卡洛夫阶到上卡洛夫阶之间。它们被归类在著名的蓼属植物 (Zieten) 下。另一方面，这组较小的标本与一个物种非常相似，该物种之前曾被描述为来自卡奇上卡洛维亚年轻地平线的 Phlycticeras schaumburgi (Waagen)。它在靠近成虫孔的腹腔中有一个奇特的“公鸡”状的化脓龙骨。长期以来，Phlycticeras-Oecoptychius 一直被认为是一个可能的双态对，但这里显示出许多不一致的地方来支持这些观点。相反，在 Phlycticeras 和 P.polygonium-P 中探索了性二态性。schaumburgi 被提议作为可能的 antidimorphs。在欧洲的不同地层组合中发现了类似的关联。有趣的是，这两种变体在 Phlycticeras 属内表现出平行的进化变化。