Synchrotron imagery of phosphatized eggs in Waptia cf. W. fieldensis from the middle Cambrian (Miaolingian, Wuliuan) Spence Shale of Utah

Abstract Exceptionally preserved fossil eggs and embryos provide critical information regarding paleoembryogenesis, reproductive strategies, the early ontogeny of arthropods, but rarity preservation both egg-bearing organisms in situ limits their use detailed evolutionary developmental (evo-devo) studies. Burgess Shale-type deposits preserve rare instances arthropods as carbonaceous compressions; however, are usually poorly with no compelling evidence embryos. We describe first record a brooding specimen Waptia cf. W . fieldensis from Spence Shale, Cambrian (Wuliuan Stage) deposit northeastern Utah southeastern Idaho. This is an arthropod Shale it exhibits two distinct modes among within single clutch: carbonization phosphatization. Unlike specimens, many this also three-dimensionally. In addition, synchrotron radiation X-ray tomographic microscopy reveals internal distributions mineral phases, along potential remnants egg membrane attachment structures, but, explicit traces developing The highlight existence diagenetic microenvironments some eggs, not others during fossilization.