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标题：Analysis of septal spacing and septal crowding in Devonian and Carboniferous ammonoids
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作者：Sophie Marie Beck ; Kenneth De Baets ; Christian Klug 等
期刊名称：Swiss Journal of Palaeontology
印刷版ISSN：1664-2376
电子版ISSN：1664-2384
出版年度：2021
卷号：140
期号：1
页码：1-21
DOI：10.1186/s13358-021-00235-x
语种：English
出版社：SpringerOpen
摘要：Abstract Septal crowding is widely known as a sign of maturity in conchs of ammonoids and nautiloids. However, reduced septal spacing may also occur as a consequence of adverse ecological conditions. Here, we address the question how septal spacing varied through ontogeny in representatives of some of the major clades of Devonian and Carboniferous ammonoids. We found that the degree of ontogenetic variation is similar between clades and that variation is only weakly linked with conch form. The results show that septal crowding alone is insufficient to identify adulthood in ammonoids; intermediate septal crowding is a common phenomenon and occurs in various growth stages. Changes in septal distances during ontogeny were, in addition to adulthood of the individuals, a passive reaction likely caused by fluctuating environmental conditions.