Early Cambrian Metazoan Eggs, Embryos, and Phosphatic Microfossils from Northwestern Canada

Three-dimensionally phosphatized, spherical fossils, interpreted as metazoan eggs and embryos on the basis of taphonomic features and cleavage patterns, are reported for the first time from the Cambrian of North America. These microfossils occur with a phosphatized biota of skeletonized fossils, including specimens indicative of the earliest Cambrian Anabarites–Protohertzina Zone in the Wernecke Mountains of eastern Yukon Territory, northwestern Canada. They range in size from 0.25 mm to more than 1.0 mm in diameter and can be referred to two genera, Olivooides Qian, 1977 and Archaeooides Qian, 1977. The North American discovery extends the biogeographic range of earliest Cambrian eggs and embryos from coeval successions in China and Siberia, suggesting a wide geographic distribution of these taxa, and emphasizes the crucial role of local environmental and taphonomic conditions in preserving this phosphatic window into the record of early animal evolution. In addition to previously reported taxa, the phosphatized biota also include indeterminate spheroids, fused clusters of Protohertzina siciformis Missarzhevsky, 1973, the enigmatic rodlike fossil Zhejiangorhabdion comptum Yue and Zhao, 1993, phosphatized fossils, including Paradoxiconus typicalis Qian et al., 2001, protoconularid Carinachites sp., and phosphatic tubes assigned to Hyolithellus cf. H. isiticus Missarzhevsky, 1969, cf. Pseudorthotheca sp., and ?Rugatotheca sp.