Patterns of intraspecific variation through ontogeny–a case study of the Cretaceous nautilid Eutrephoceras dekayi and modern Nautilus pompilius

The magnitude and ontogenetic patterns of intraspecific variation can provide important insights into the evolution and development of organisms. Understanding the intraspecific variation of organisms is a key to correctly pursuing studies in major fields of palaeontology. However, intraspecific variation has been largely overlooked in ectocochleate cephalopods, particularly nautilids. Furthermore, little is known regarding the evolutionary pattern. Here, we present morphological data for the Cretaceous nautilid Eutrephoceras dekayi (Morton, 1834) and the modern nautilid Nautilus pompilius Linnaeus, 1758 through ontogeny. The data are used to describe the change of conch morphology and to elucidate the evolutionary patterns of intraspecific variation. We discovered the presence of morphological changes at hatching and maturity, which is shared in every conch parameter in E. dekayi and N. pompilius. We also found that intraspecific variation is high in early ontogeny in both taxa, follow...

种内变异（intraspecific variation）的幅度与个体发育模式，可为生物的演化与发育研究提供重要参考依据。明晰生物的种内变异，是正确开展古生物学（palaeontology）核心领域研究的关键所在。然而，外壳头足类（ectocochleate cephalopods），尤其是鹦鹉螺类（nautilids）的种内变异长期以来被大幅忽视。此外，学界对其演化模式的认知仍较为匮乏。本研究针对白垩纪（Cretaceous）鹦鹉螺类物种德凯真卷壳鹦鹉螺（Eutrephoceras dekayi，莫顿，1834）与现生鹦鹉螺类物种珍珠鹦鹉螺（Nautilus pompilius，林奈，1758）的全个体发育过程采集形态学数据。该数据用于描述壳体形态（conch morphology）的变化，并阐明种内变异的演化模式。本研究发现，两类物种在孵化期与成熟期均存在形态变化，且该特征覆盖德凯真卷壳鹦鹉螺与珍珠鹦鹉螺的所有壳体参数。同时，本研究还发现，两类群的早期个体发育阶段种内变异程度均较高，后续……