The feeding organ of cephalopod species, the beak, can be used to reveal important ecological information. In this study, geometric morphometric approaches were employed to investigate the phylogenetic relevance and classification effect of beak lateral profile shape. The two‐dimensional beak morphologies of 1164 pairs of 24 species from 13 genera and five families were constructed, and their evolutionary relationships and taxonomic status were confirmed using geometric morphometrics and molecular biology approaches. We also assessed the phylogenetic signals of beak shape. The analysis results show shape variation in the beak mainly in the rostrum, hood, and lateral wall. The overall shape parameters (all PCs) of the upper and lower beak are more useful for species identification. The shapes of the upper and lower beak show a strong phylogenetic signal, and the phenogram based on the beak shape basically reflected the families’ taxonomic positions. We also hypothesized that the shape variation in the beaks of cephalopods may be ascribed to genetic and environmental differences. In summary, beaks are a reliable material for the classification of cephalopod species. Geometric morphometric approaches are a powerful tool to reveal the identification, phylogenetic relevance and phenotypic diversity of beak shape in cephalopods.

中文翻译：

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几何形态计量学揭示头足类喙形态的系统发育相关性

头足类动物的摄食器官——喙，可以用来揭示重要的生态信息。本研究采用几何形态计量学方法研究喙侧剖面形状的系统发育相关性和分类效果。构建了5科13属24种1164对的二维喙形态，并利用几何形态测量学和分子生物学方法证实了它们的进化关系和分类地位。我们还评估了喙形状的系统发育信号。分析结果显示喙的形状变化主要集中在喙部、喙部和侧壁。上喙和下喙的整体形状参数（所有 PC）对于物种识别更有用。上下喙的形状显示出强烈的系统发育信号，基于喙形状的表型图基本反映了科的分类位置。我们还假设头足类动物喙的形状变化可能归因于遗传和环境差异。综上所述，喙是头足类物种分类的可靠材料。几何形态测量方法是揭示头足类动物喙形状的识别、系统发育相关性和表型多样性的有力工具。