Losso Sarah R, Nanglu Karma, Weyland Walker C, Ortega-Hernández Javier
Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA, 02138, USA.
Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks St, Toronto, ON, M5S 3B2, Canada.
BMC Biol. 2025 Aug 4;23(1):238. doi: 10.1186/s12915-025-02335-3.
Euarthropod appendages are specialized for diverse roles including feeding, walking, and mating, which require precise morphologies and ranges of motion. Cambrian fossils preserve exceptional details of extinct euarthropod appendages that can illuminate their anatomy and ecology. However, fossils are typically restricted by small sample sizes or incomplete preservation, and thus functional studies of the appendages usually rely on idealized reconstructions. The Burgess Shale Olenoides serratus is unique among trilobites owing to the availability of numerous specimens with soft tissue preservation that allow us to quantify its appendages' functional morphology.
We measured the range of motion of the legs in Olenoides serratus and the extant horseshoe crab Limulus polyphemus. Despite repeated ecological comparisons between trilobites and xiphosurans, we find significant differences in the appendages' mobility between these taxa, with Limulus showing greater flexibility between the podomeres.
O. serratus legs have a more restricted range of motion relative to L. polyphemus, particularly in their distal region. Flexure between the protopodite played a critical role in allowing the endopodite to create known trilobite trace fossils and bring food toward the ventral groove.
真节肢动物的附肢专门用于多种功能,包括进食、行走和交配,这需要精确的形态和运动范围。寒武纪化石保留了已灭绝真节肢动物附肢的非凡细节,能够阐明其解剖结构和生态。然而,化石通常受限于小样本量或保存不完整,因此对附肢的功能研究通常依赖于理想化的重建。布尔吉斯页岩的锯齿奥氏虫在三叶虫中很独特,因为有大量保存了软组织的标本,这使我们能够量化其附肢的功能形态。
我们测量了锯齿奥氏虫和现存鲎的腿部运动范围。尽管对三叶虫和剑尾目的生态进行了多次比较,但我们发现这些类群的附肢活动能力存在显著差异,鲎在体节之间表现出更大的灵活性。
相对于鲎,锯齿奥氏虫的腿部运动范围更受限,尤其是在其远端区域。原肢节之间的弯曲在使内肢节形成已知的三叶虫痕迹化石并将食物带向腹沟方面起到了关键作用。