A rare onychophoran-like lobopodian from the Lower Cambrian Chengjiang Lagerstätte, southwestern China, and its phylogenetic implications

Lobopodians, which diversified and flourished in the Cambrian seas, have long drawn much attention in that not only their extant close relatives, onychophorans and tardigrades, but euarthropods (Chelicerata, Myriapoda, Crustacea, and Hexapoda) may have been deeply rooted in stem-group lobopodians. Antennacanthopodia gracilis new genus and species is described and interpreted here as an “unarmoured” lobopodian from the Chengjiang fossil Lagerstätte (Early Cambrian, —520 Ma), Yunnan, southwestern China. This animal shares with other known Cambrian lobopodians such plesiomorphies (primitive characters) as onychophoran-like overall appearance; a metamerically segmented body covered by slightly sclerotized cuticle, and paired, unjointed lobopodal legs. Antennacanthopodia is also featured by a pair of frontal antennae, potential ocellus-like lateral visual organs, second antennae, a straight, voluminous midgut, diminutive spines arrayed on the leg and the trunk, well-developed leg musculature, highly sclerotized terminal leg pads, and presumptively a pair of posteriormost appendicules. This new taxon, with innovative characters (autapomorphies), furthers our understanding of early lobopodian diversification. Antennacanthopodia is considered closely allied to extant Onychophora based on considerable anatomical similarities. Taken together its “two-segmented” cephalization and appendage-bearing “ocular segment”, this new form may shed some new light on the arthropod groundplan.