''Pywackia'' is a contentious
Cambrian
The Cambrian Period ( ; sometimes symbolized C with bar, Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million ...
fossil
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
that has been interpreted as the earliest (
total group
In phylogenetics, the crown group or crown assemblage is a collection of species composed of the living representatives of the collection, the most recent common ancestor of the collection, and all descendants of the most recent common ancestor. ...
)
Bryozoan, and the only representative of that
phylum
In biology, a phylum (; plural: phyla) is a level of classification or taxonomic rank below kingdom and above class. Traditionally, in botany the term division has been used instead of phylum, although the International Code of Nomenclature f ...
in the Cambrian period.
Its Bryozoan credentials have been called into question, but the
octocoral
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 ...
alternative is equally unconvincing, and there are reasons to suggest a position in the
Stenolaemata stem lineage.
References
{{Taxonbar, from=Q20817953
Fossils of Mexico
Enigmatic prehistoric animal genera
Cambrian invertebrates
Cambrian fossil record
Fossil taxa described in 2010
Cambrian genus extinctions