biostudies-literatureUnknown27(8)Liu CNSFCThe origin and evolution of trilobated body plan of the Artiopoda, a group of epibenthic euarthropods from Cambrian Lagerstätten, remain unclear. Here we examine old and new specimens of <i>Urokodia aequalis</i>, one of euarthropods from the Chengjiang biota, revealing new morphological details and revising its taxonomy. <i>Urokodia</i> possesses an elongate body with a five-segmented head, a thorax with 13-15 tergites, and a three-segmented pygidium with well-defined axial region. The ventral morphology includes paired stalked eyes, one fleshy antenna pair, the following homogeneous head and thoracic appendages, each with an annular proximal-element, an articulated stenopodous branch and a lamellar flap, and the pygidial appendages solely consisting of lamellar flaps. Cladistic analyses resolved <i>Urokodia</i> as the basal-most member of the Artiopoda, offering a hypothesis of the initial origin of trilobation in the pygidium. The new data, in conjunction with the presence of the elongated body plan across major lineages of euarthropods, suggest a convergent evolution of this trait.iScience110443https://www.ebi.ac.uk/biostudies/studies/S-EPMC11325232biostudies-literatureCambrian euarthropod <i>Urokodia aequalis</i> sheds light on the origin of Artiopoda body plan.PMC11325232Fu DZhang XLiu CWu YfalseCambrian euarthropod <i>Urokodia aequalis</i> sheds light on the origin of Artiopoda body plan.The origin and evolution of trilobated body plan of the Artiopoda, a group of epibenthic euarthropods from Cambrian Lagerstätten, remain unclear. Here we examine old and new specimens of <i>Urokodia aequalis</i>, one of euarthropods from the Chengjiang biota, revealing new morphological details and revising its taxonomy. <i>Urokodia</i> possesses an elongate body with a five-segmented head, a thorax with 13-15 tergites, and a three-segmented pygidium with well-defined axial region. The ventral morphology includes paired stalked eyes, one fleshy antenna pair, the following homogeneous head and thoracic appendages, each with an annular proximal-element, an articulated stenopodous branch and a lamellar flap, and the pygidial appendages solely consisting of lamellar flaps. Cladistic analyses resolved <i>Urokodia</i> as the basal-most member of the Artiopoda, offering a hypothesis of the initial origin of trilobation in the pygidium. The new data, in conjunction with the presence of the elongated body plan across major lineages of euarthropods, suggest a convergent evolution of this trait.2024-01-01T00:00:00Z2024 Aug2025-04-19T20:42:35.917Z2025-04-19T20:42:35.917ZS-EPMC113252323914871310.1016/j.isci.2024.110443