Anatomy and lifestyle of Kunmingella (Arthropoda, Bradoriida) from the Chengjiang fossil Lagerstatte (lower Cambrian; Southwest China)

An updated reconstruction of the body plan, functional anatomy and life att itude of the bradoriid arthropod Kunmingella is proposed, based on new foss il specimens with preserved soft parts found in the lower Cambrian of Cheng jiang and Haikou (Yunnan, SW China) and on previous evidence. The animal ha s a single pair of short antennae pointing towards the front (a setal patte rn indicates a possible sensory function). The following set of seven appen dages (each composed of a 5-segmented endopod and a leaf-like exopod fringe d with setae) is poorly differentiated, except the first three pairs (with possible rake-like endopodial outgrowths, smaller exopods) and the last pai r of appendages (endopod with longer and more slender podomeres). The endop ods are interpreted as walking legs with a possible role in handling food p articles (marginal outgrowth with setae). The leaf-like exopods may have ha d a respiratory function. The trunk end is short, pointed, flanked with fur cal-like rami and projects beyond the posterior margin of the carapace. The attachment of the body to the exoskeleton is probably cephalic and apparen tly lacks any well-developed adductor muscle system. The inferred life atti tude of Kunmingella (e.g. crawling on the surface of the sediment) was that of a dorsoventrally flattened arthropod capped by a folded dorsal shield ( ventral gape at least 120 degrees), thus resembling the living ostracode Ma nawa. The animal was also probably able to dose its carapace as a response to environmental stress or to survive unfavourable conditions (e.g. buried in sediment). The anterior lobes of the valves are likely to have accommoda ted visual organs (possibly lensless receptors perceiving ambient light thr ough the translucent head shield). Preserved eggs or embryos suggest a poss ible ventral brood care. The presence of Kunmingella in coprolites and its numerical abundance in Chengjiang sediment indicate that bradoriids constit uted an important source of food for larger predators. Kunmingella differs markedly from the representatives of the crown group Crustacea (extant and Cambrian taxa) and from the stem group derivatives of Crustacea (exemplifie d by phosphatocopids and some 'Orsten' taxa) in showing no major sign of li mb specialization (e.g. related to feeding strategies). Although it resembl es other Chengjiang euarthropods in important aspects of its body plan (e.g . uniramous antennae, endopod/exopod configuration), Kunmingella possesses several features (e.g. antennal morphology, post-antennular appendages with 5-segmented endopods) which support the view that bradoriids may be very e arly derivatives of the stem line Crustacea.