Margaretia

Margaretia is a frondose organism known from the middle Cambrian Burgess shale and the Kinzers Formation of Pennsylvania. Its fronds reached about 10 cm in length and are peppered with a range of length-parallel oval holes. It was originally interpreted as an alcyonarian coral. It was later reclassified as a green alga closely resembling modern Caulerpa by D.F. Satterthwait in her Ph.D. thesis in 1976, a finding supported by Conway Morris and Robison in 1988. More recently, it has been treated as an organic tube, that is used as nest of hemichordate Oesia.