Origins and early evolution of arthropods

Phylogenomics reconstructs an arthropod tree in which a monophyletic A rthropoda splits into P ycnogonida +  E uchelicerata and M yriapoda +  P ancrustacea. The same chelicerate–mandibulate groups are retrieved with morphological data sets, including those encompassing most taxa known from P alaeozoic K onservat‐ L agerstätten. With respect to the interrelationships of the three extant clades of P anarthropoda, a sister group relationship between O nychophora and A rthropoda is endorsed by transcriptomics and micro RNA s, although this hypothesis forces homoplasy in characters of the segmental ganglia that are shared by tardigrades and arthropods. Cambrian lobopodians, dinocaridids, bivalved arthropods and fuxianhuiids document the successive appearance of characteristic arthropod features in the stem lineage of E uarthropoda (crown‐group arthropods). Molecular dating suggests that arthropods had their origin and initial diversification in the E diacaran, but no convincing palaeontological evidence for P anarthropoda is available until the earliest Cambrian.