Morpho-anatomy of the lobopod Magadictyon cf. haikouensis from the Early Cambrian Chengjiang Lagerstatte, South China

Magadictyon haikouensis (Luo and Hu, 1999) from the Early Cambrian Chengjiang Lagerstatte, an incomplete specimen of a large lobopod with strong appendages, has been regarded as related to the lobopods Microdictyon and Onychodictyon. Newly discovered complete specimens of Magadictyon cf. haikouensis (found by the Early Life Institute field team) show that the taxon, in addition to its strong appendages with appendicules, also had a head bearing similar caecum-like structures to those of the arthropod Naraoia and Chelicerate, 'Peytoia'-like mouthparts and frontal appendages. Because of their similarity, the caecum-like structures of Magadictyon cf. haikouensis are considered to be homologous with those of stem-group arthropods. The 'Peytoia'-like mouthparts and the frontal appendages are similar to those of the AOPK (Anomalocaris-Opabinia-Pambdelurion-Kerygmachela) group. In addition, the appendages with appendicules show that Magadictyon cf. haikouensis is closely related to Onychodictyon. Therefore, Magadictyon cf. haikouensis is regarded here as a rare transitional form between lobopods and arthropods. Besides, together with other lobopods, the morphology of Magadictyon cf. haikouensis demonstrates that the Cambrian lobopods appear to have been diverse and not particularly closely related to one another, and do not seem to represent a monophyletic clade.