For over a year and a half now, it's been widely believed that there was a stem bryozoan in the Cambrian. Our faithful reporter of fascinating fieldtrips, Inyo,
sent us an announcement of its discovery back then. He wrote:

"A paper just published online, and now available for pdf download (as of October 27, 2021), describes what the authors call a potential
stem-group bryozoan, preserved as secondarily mineralized--phosphatized--specimens from Cambrian Stages 4 and 3,
Australia (Wirrealpa Limestone) and South China (Dengying Formation), respectively. They call it Protomelission gatehousei, whose original unmineralized body plan shares traits with several Bryozoa classes,
including the soft-bodied Gymnolaemata (Ctenostomata)."
[end of excerpt from:]
First Early Cambrian Bryozoa Discovered https://groups.google.com/g/sci.bio.paleontology/c/AJOJSQ62AGY/m/boHZ8lYgLgAJ Oct 27, 2021, 8:43:37 PM

Alas, this early putative bryozoan may not even be an animal.

Back in March, _Nature_ published the following article:

"Protomelission is an early dasyclad alga and not a Cambrian bryozoan"
Jie Yang, Tian Lan, Xi-guang Zhang & Martin R. Smith
Nature volume 615, pages 468–471 (2023) https://www.nature.com/articles/s41586-023-05775-5

I get the impression that the article is paywalled, but I have full access to it
through the subscription of our university library.

ABSTRACT
"The animal phyla and their associated body plans originate from a singular burst of evolution occurring during the Cambrian period, over 500 million years ago1. The phylum Bryozoa, the colonial ‘moss animals’, have been the exception: convincing
skeletons of this biomineralizing clade have been absent from Cambrian strata, in part because potential bryozoan fossils are difficult to distinguish from the modular skeletons of other animal and algal groups2,3. At present, the strongest candidate4 is
the phosphatic microfossil Protomelission5. Here we describe exceptionally preserved non-mineralized anatomy in Protomelission-like macrofossils from the Xiaoshiba Lagerstätte6. Taken alongside the detailed skeletal construction and the potential
taphonomic origin of ‘zooid apertures’, we consider that Protomelission is better interpreted as the earliest dasycladalean green alga—emphasizing the ecological role of benthic photosynthesizers in early Cambrian communities. Under this
interpretation, Protomelission cannot inform the origins of the bryozoan body plan; despite a growing number of promising candidates7,8,9, there remain no unequivocal bryozoans of Cambrian age."


There are lots of microphotographs, and plenty of references, some of which dispute other claimed Cambrian bryozoans.

Just in case the photographs aren't paywalled, I'm giving a link to Fig. 2, which shows
putative *Protomelission* fossils.

https://www.nature.com/articles/s41586-023-05775-5/figures/2


Feel free to ask questions and make requests.


Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--
University of South Carolina
http://people.math.sc.edu/nyikos

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