A new arthropod appendage from the Guanshan Biota (Cambrian) and the functional diversity of arthropod suspension-feeding over the Phanerozoic

Suspension-feeders, animals that capture floating particles from a suspension, have been crucial to the evolution of marine ecosystems throughout the Phanerozoic. Suspension-feeding arthropods today are varied in prey, habitat or movement, and their fossil record is increasingly unveiling their evolution within this niche. We report a new species of suspension-feeding arthropod from the Guanshan Biota (Cambrian Stage 4, South China) based on rake-like appendages and analyse the functional diversity of arthropod suspension-feeders, comparing Early Palaeozoic species with today. Comparatively, two distinct functional groups have gone extinct: Cambrian suspension-feeders specialized in capturing mesozooplankton close to their own size and predominantly Ordovician ‘giant’ suspension-feeders with a role functionally analogous to current large aquatic vertebrates. The Guanshan arthropod represents an extreme case of the first group, and its ecological role deviates from that of potentially closely related species, exemplifying the unique local conditions of its environment. The identification of these two groups highlights the complex ecosystemic changes undergone between the Cambrian and Ordovician and the ecological shifts of suspension-feeding arthropods across the Phanerozoic.