The Veneridae are the most speciose modern family of bivalves, and one of the most morphologically conservative and homoplastic, making subfamily- and sometimes even genus-level classification difficult. The widespread Cretaceous genus Legumen Conrad, 1858 is currently placed in the subfamily Tapetinae of the Veneridae, although it more closely resembles the Solenoida (razor clams, Pharidae and Solenidae) in general shell form. Here we provide high-resolution images of the Legumen hinge for the first time. We confirm from hinge morphology that Legumen belongs in Veneridae, but it should be referred to incertae subfamiliae, rather than retained in the Tapetinae, particularly in light of the incomplete and unstable understanding of venerid systematics. Legumen represents a unique hinge dentition and a shell form—and associated life habit—that is absent in the modern Veneridae despite their taxonomic diversity. Veneridae are hyperdiverse in the modern fauna, but strikingly ‘under-disparate,’ having lost forms while gaining species in the long recovery from the end-Cretaceous extinction.

中文翻译：

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Legumen Conrad 的铰链和生态形态学，1858 年（双壳类动物，Veneridae），以及白垩纪末灭绝后 venerid morphospace 的收缩

Veneridae 是最有特色的现代双壳类科，也是形态上最保守和同质的科之一，使得亚科，有时甚至是属级分类变得困难。分布广泛的白垩纪属豆类Conrad, 1858 目前被归入 Veneridae 的 Tapetinae 亚科，尽管它更接近于一般壳形式的 Solenoida（剃刀蛤、Pharidae 和 Solenidae）。在这里，我们提供高分辨率图像豆类第一次铰链。我们从铰链形态证实豆类属于 Veneridae，但它应该被称为 incertae subfamiliae，而不是保留在 Tapetinae 中，特别是考虑到对 venerid 系统学的不完整和不稳定的理解。豆类代表独特的铰链齿列和贝壳形式 - 以及相关的生活习惯 - 尽管它们的分类多样性，现代 Veneridae 中不存在。Veneridae 在现代动物群中是高度多样化的，但惊人地“完全不同”，在从白垩纪末期灭绝的漫长恢复过程中获得物种的同时失去了形态。