''Margaretia'' is a

frondose Frondosity (from Latin ''frondōsus'' meaning 'leafy') is the property of an organism that normally flourishes with fronds or leaf-like structures. Many frondose organisms are thalloid and lack the organization of tissues into organs, with the ...

organism known from the middle Cambrian

Burgess shale The Burgess Shale is a fossil-bearing deposit exposed in the Canadian Rockies of British Columbia, Canada. It is famous for the exceptional preservation of the soft parts of its fossils. At old (middle Cambrian), it is one of the earliest foss ...

and the

Kinzers Formation The Kinzers Formation is a geologic formation in Pennsylvania. It preserves fossils dating back to the Cambrian Period. The base of the Kinzers Formation is primarily a dark-brown shale. The middle is a gray and white spotted limestone and, lo ...

Pennsylvania Pennsylvania (; ( Pennsylvania Dutch: )), officially the Commonwealth of Pennsylvania, is a state spanning the Mid-Atlantic, Northeastern, Appalachian, and Great Lakes regions of the United States. It borders Delaware to its southeast, ...

. 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 Octocorallia (also known as Alcyonaria) is a class of Anthozoa comprising around 3,000 species of water-based organisms formed of colonial polyps with 8-fold symmetry. It includes the blue coral, soft corals, sea pens, and gorgonians (sea fan ...

coral Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and sec ...

. It was later reclassified as a green alga closely resembling modern ''

Caulerpa ''Caulerpa'' is a genus of seaweeds in the family Caulerpaceae (among the green algae). They are unusual because they consist of only one cell with many nuclei, making them among the biggest single cells in the world. A species in the Mediterran ...

'' by D.F. Satterthwait in her Ph.D. thesis in 1976,Donna Fields Satterthwait, Paleobiology and Paleoecology of Middle Cambrian Algae from Western North America, Ph.D. Thesis University of California at Los Angeles, 1976. a finding supported by Conway Morris and Robison in 1988.S.Conway Morris and R.A. Robison, "More soft-bodied Animals and Algae from the Middle Cambrian of Utah and British Columbia", University of Kansas Paleontological Contributions, Paper 122, pages 8-11, 1988

/ref> More recently, it has been treated as an organic tube, that is used as nest of

hemichordate Hemichordata is a phylum which consists of triploblastic, enterocoelomate, and bilaterally symmetrical marine deuterostome animals, generally considered the sister group of the echinoderms. They appear in the Lower or Middle Cambrian and include ...

Oesia ''Oesia disjuncta'' is a monospecific genus known from the Middle Cambrian Burgess Shale. 1147 specimens of ''Oesia'' are known from the Greater Phyllopod bed, where they comprise 2.18% of the community. Despite some similarities to the chaetogna ...

''.

References

External links

* Burgess Shale fossils Wheeler Shale Incertae sedis {{cambrian-stub