Cubozoan Embryos From The Early Cambrian Kuanchuanpu Formation, South China

Tissue-differentiated Cnidaria is one of the phylum with a fixed radial symmetry body configurations. At present, most scholars believe that abundant phosphatization embryo fossils from the early Cambrian Kuanchuanpu Formation, in Ningqiang County, Shaanxi, south China belonged to cnidarians. However, all of them remain unnamed in taxonomy on account of the scarcity of embryo fossils with soft tissues, the lack of research of the ontogenetic variations and the taphonomic diagenesis. The research of pentamarous cnidarian fossils has made a great progress. Some pentamarous embryo fossils with unprecedentedly interior anatomy were suggested as a stem group of cubozoans.For further investigation of the interior anatomy and classification of the embryo fossils, we examined new-collected microfossils with Micro-CT in Xi’an Jiaotong University, China and in Tohoku University, Japan. The Micro-CT and Synchrotron data obtained were processed using VG Studio 2.2 Max to enhance legibility of key internal anatomies by using artificial colors and to render detailed non-destructive 3-dimensional reconstructions of these microscopic fossils. Especially, the holotype specimen preserves many unequivocal internal anatomies, including coronal muscles, perradial and adradial frenula, accessory septum, gonad-lamellae, tentacle buds and perradial pockets. Compared with previously described co-occurring medusozoan fossils, the contrasting disposition between the accessory septa and gonad lamellae of Nympharum cornica gen. et sp. nov. provide valuable hints on the evolution of the medusozoan gonads.