Spirula spirula (Coleoidea: Decabrachia) is a unique deep-sea squid with an uncertain taxonomic status. Here, we apply geometric morphometric analyses to precisely describe changes in conch morphology during the course of ontogeny of 21 specimens collected from 12 localities worldwide. These data were used to explore whether the genus is monospecific or comprises several species. Different 2D and 3D conch parameters are presented based on micro-computed tomography data, combining noninvasive imaging techniques with a range of morphometric analyses. Our data imply that Atlantic and Indo-Pacific specimens form two distinct morphological clusters, potentially representing two pseudocryptic species or two populations undergoing divergence (i.e. in the process of speciation). Given the evolutionary trend from straight to more coiled forms, we suggest that S. spirula represents a neotenous form that migrated from the Indo-Pacific towards the Atlantic via the Agulhas leakage, which has been active since the closure of the Strait of Panama (10–3 Ma).

中文翻译：

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螺旋藻属中是否存在一种以上的物种（头足类：Decabrachia）：大西洋-太平洋分界线的证据

螺旋藻（Coleoidea: Decabrachia）是一种独特的深海鱿鱼，分类地位不确定。在这里，我们应用几何形态学分析来精确描述从全球 12 个地区采集的 21 个标本在个体发育过程中的海螺形态变化。这些数据用于探索该属是单特异性的还是包含多个物种。不同的 2D 和 3D 海螺参数基于微计算机断层扫描数据呈现，将无创成像技术与一系列形态分析相结合。我们的数据表明大西洋和印度太平洋标本形成了两个不同的形态学集群，可能代表两个伪隐蔽物种或两个正在分化的种群（即在物种形成过程中）。鉴于从直线形式到更卷曲形式的进化趋势，