https://www.utoronto.ca/news/rare-find-burgess-shale-preserved-embryos-inside-508-million-year-old-waptia-fossil
Rare find at Burgess Shale: preserved embryos inside 508-million-year-old Waptia fossil |...
Long before kangaroos carried their joeys in their pouches and honey bees nurtured their young in hives, there was the 508-million-year-old Waptia.