Margaretia

Margaretia is a genus of frond shaped fossil organism known from the Middle Cambrian Burgess Shale of British Columbia and the Kinzers Formation of Pennsylvania, with a single recognized species, M. dorus, first described by Charles Walcott in 1931. Its fronds reached about 10 centimeters long and carried rows of parallel oval holes. Its classification has shifted repeatedly: it was first described as a coral, then reinterpreted as a green alga resembling modern Caulerpa, and more recently proposed as an organic tube that served as a nest for the hemichordate worm Oesia, leaving its true biological affinity unresolved.