Early Cambrian phosphatized blastula- and gastrula-stage animal fossils from southern Shaanxi

Marine invertebrate animal embryos and their early developmental products are of great significance to the study of taxonomy and phylogeny of early animals. A great number of phosphatized globular fossils were collected from the early Cambrian Kuanchuanpu Member (upper Dengying Formation), southern Shaanxi, and a nearly complete developmental sequence — from a fertilized egg, via blastodisc formation, blastula development, blastodisc enlargement toward gastrulae, to tissue differentiation — can be discerned in this collection. This discovery provides unmatchable material for studies on the origin, taxonomy, radiation, and ontogeny of early metazoans.