From the Cover: A superarmored lobopodian from the Cambrian of China and early disparity in the evolution of Onychophora

We describe Collinsium ciliosum from the early Cambrian Xiaoshiba Lagerstätte in South China, an armored lobopodian with a remarkable degree of limb differentiation including a pair of antenna-like appendages, six pairs of elongate setiferous limbs for suspension feeding, and nine pairs of clawed annulated legs with an anchoring function. Collinsium belongs to a highly derived clade of lobopodians within stem group Onychophora, distinguished by a substantial dorsal armature of supernumerary and biomineralized spines (Family Luolishaniidae). As demonstrated here, luolishaniids display the highest degree of limb specialization among Paleozoic lobopodians, constitute more than one-third of the overall morphological disparity of stem group Onychophora, and are substantially more disparate than crown group representatives. Despite having higher disparity and appendage complexity than other lobopodians and extant velvet worms, the specialized mode of life embodied by luolishaniids became extinct during the Early Paleozoic. Collinsium and other superarmored lobopodians exploited a unique paleoecological niche during the Cambrian explosion.Onychophorans, or velvet worms, comprise a relatively small phylum (∼180 species) of soft-bodied panarthropods constituting a minor component of modern rainforest ecosystems around the world (1). The overall organization of extant onychophorans is remarkably conserved (2), typified by a low morphological variability and homogeneous autoecologies as ambush predators of small invertebrates. An emerging fossil record, however, points to a substantially wider range of forms and habits during their early evolutionary history (3–8). Paleozoic lobopodians—a paraphyletic group of soft-bodied extinct organisms resembling worms with legs—occupy basal phylogenetic positions within the stem lineages of Onychophora, Tardigrada, and Euarthropoda (3, 6, 9), and thus offer critical insights about the early evolution and paleobiology of panarthropod phyla. Here, we describe the stem group onychophoran Collinsium ciliosum, a “superarmored” lobopodian with complex limbs, based on a large and exquisitely preserved population from the early Cambrian (Stage 3) Xiaoshiba Lagerstätte in South China (10, 11) (SI Appendix, Fig. S1).