Morphological disparity and ontogeny of the endemic heteromorph ammonite genus Aegocrioceras (Early Cretaceous, Hauterivian, NW-Germany)
Morphological disparity and ontogeny of the endemic heteromorph ammonite genus Aegocrioceras (Early Cretaceous, Hauterivian, NW-Germany)
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DOI：
10.1016/j.palaeo.2019.01.020
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发表时间：
2019-04-15
影响因子：
3
通讯作者：
De Baets, Kenneth
中科院分区：
文献类型：
--
作者：
Hoffmann, Rene;Weinkauf, Manuel F. G.;De Baets, Kenneth
尽管异型菊石经常表现出大范围的种内变异，但这种变异很少被量化。在这里，我们量化了85个新收集的Hauterivian地方性鹦鹉螺属（Aegocrioceras）标本的种内变异和个体发育。所有标本均采集自德国西北部（下萨克森州盆地）Resse粘土坑最近暴露的82层的结核。使用新软件conch (C)以45度的步骤收集海螺的形态数据（直径、螺纹高度、螺纹间距、肋间距）。CONCH(C)软件将随本出版物正式发布。所有菊石被先验地鉴定为a . bicarinatum或a . semicinctum。对这一组合的种内和种间变异以及个体发育的评估表明，只有一个物种的存在，即A. bicarinatum。与a . bicarinatum和a . semicinctum的类型材料比较发现，不同的海螺参数在形态上有很大的重叠，并不支持这两种形式作为不同物种的分离。所分析的双头螺组合在螺的形态上有很大的差异，包括螺的间距、脐宽和螺的膨胀。此外，通过个体发生对种内变异的变化进行了量化，并讨论了组合内性别二态性的存在或不存在。
Despite the fact that heteromorph ammonites often show a large range of intraspecific variation, that variation has rarely been quantified. Here, we quantify the intraspecific variation and ontogeny of 85 newly collected specimens of the Hauterivian endemic ammonite genus Aegocrioceras. All specimens were collected from concretions in the recently exposed bed 82 in the clay pit Resse in NW Germany (Lower Saxony Basin). Data for the conch morphology (diameter, whorl height, whorl interspace, rib spacing) were collected in 45 degrees steps using the new software CONCH(C). The CONCH(C) software will be made officially available with this publication. All ammonites were a priori identified as A. bicarinatum or A. semicinctum. An assessment of the intra- and interspecific variation as well as the ontogeny of this assemblage demonstrates the presence of just one species, i.e., A. bicarinatum. Comparison with the type material of A. bicarinatum and A. semicinctum reveals a large morphological overlap of different conch parameters and does not support a separation of both forms as distinct species. The analyzed assemblage of A. bicarinatum has a high variation in conch morphology including whorl interspace, umbilical width, and whorl expansion. Furthermore, the changes in intraspecific variation through ontogeny were quantified and the presence or absence of sexual dimorphism within the assemblage is discussed.