The bonnethead Sphyrna tiburo is a wide-spread, small species of coastal hammerhead shark with a long history of taxonomic uncertainty, including, according to some authors, disjoint subspecies in the western Atlantic and eastern Pacific oceans. The present study investigates the level of morphometric and genetic variation within the Sphyrna tiburo complex throughout most of its distributional range including the western Atlantic, the Gulf of Mexico, the Caribbean, and the eastern Pacific. A morphometric study, including a comparison of ampullary densities, and a molecular analysis of two mitochondrial genes, was performed. We analyzed variation in cephalofoil shape between and within lineages, based on landmarks and Fourier analysis of the silhouettes. All tests delineated discrete morphological groups, including differences of ampullae density for those lineages in which this information could be unambiguously assessed. Both morphometric and molecular analysis support the existence of three different evolutionarily significant units (two in the Atlantic: one northern and one south-central, and a third in the eastern Pacific) that deserve specific taxonomic status. We urge a deep taxonomic review of this complex to gather biological data on each lineage and develop adequate independent conservation strategies and actions to protect the various evolutionary units.

Graphical abstract

中文翻译：

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圆头鲨复合体 Sphyrna tiburo (Carcharhiniformes: Sphyrnidae) 的分子和形态学评价

bonnethead Sphyrna tiburo是一种分布广泛的小型沿海双髻鲨，其分类学的不确定性由来已久，据一些作者称，包括西大西洋和​​东太平洋的不相交的亚种。本研究调查了Sphyrna tiburo内的形态测量和遗传变异水平分布范围包括西大西洋、墨西哥湾、加勒比海和东太平洋。进行了形态测量研究，包括比较壶腹密度和两个线粒体基因的分子分析。我们基于轮廓的地标和傅立叶分析分析了谱系之间和谱系内的头叶形状的变化。所有测试都描绘了离散的形态组，包括可以明确评估这些信息的那些谱系的壶腹密度差异。形态计量学和分子分析都支持存在三个不同的具有进化意义的单元（大西洋中的两个：一个北部和一个中南部，第三个在东太平洋），它们值得特定的分类地位。

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