Abstract

Although knowledge of exceptional Cambrian fossil Lagerstätten has increased dramatically, relatively little information has been uncovered about the early ontogeny of ancient Metazoa. Here we describe new phosphatized eggs and embryos, partly indicating germ band formation, and the earliest known larvae of early bilaterians. Developmental sequences are reconstructed for Pseudooides- and tetramerous-type embryos. Together with these developmental sequences, patterns of germ band formation, irregular “radial” cleavage types, and unciliated larva with serial divisions and a posterior segment indicate affinities with protostomes, most probably within an ancestral arthropodan lineage.

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