Abstract

The Cambrian fossil embryos are represented by taxa of Olivooides, Pseudooides, Quadrapyrgites and Markuelia. It has previously been proposed that all these fossil embryos underwent direct development, and thus animals with direct development are deeply rooted in the Cambrian Period. Here, we report new three dimensionally phosphatized microfossils of coronate scyphozoan Qinscyphus necopinus from the Cambrian Fortunian Kuanchuanpu Formation at Zhangjiagou Lagerstätte, southern Shaanxi Province, South China. The new material includes fragmentary specimens of hatched stages with oral part preserved, and thus permits a revision of the morphology of Q. necopinus. And more important is a new type of fossil embryo that has morphology comparable with that of the hatched stages of Q. necopinus. This new embryo is thus assigned to the prehatching embryonic stage of Q. necopinus, and it demonstrates that Q. necopinus underwent direct development. Direct development is a ubiquitous development mode of the Cambrian fossil embryos, and it is proposed here that direct development may be the plesiomorphy of metazoan development.