first fossils of multicellular green algae appear in the Cambrian
strata of the early Paleozoic Era. Margaretia as shown here was
a thin, frond-like green, carbonaceous algae resembling modern
dorus fossils as seen here have also been found in the Burgess
shale of Canada and are classified as Chlorophytes,
branch of green algae from the Streptophytes that eventually
rise to the land plants.
Briggs book (see reference below) shows up to three fronds growing
from the base, the Utah fossils seen to only have single and
double fronds attached
to the base. A network of small oval holes perforates the fronds.
A few scientists believe Margaretia were a type of sponge or
coral. Margaretia are one of the more common megascopic algae in
the Wheeler and Marjum Formations, but they are usually poorly
and rarely found in the size and having the contrast of this specimen.
together with filamentous cyanobacteria (commonly called blue-green
algae), algae like Margaretia built large reef systems
that not only supported Cambrian marine life, but photosynthetically
augmented atmospheric oxygen levels thus further driving the
eukaryotic diversification known as the Cambrian
specimen ranks among the largest Margaretia ever found, and demonstrates
that the kelp-like fronds could be very long. Pictured is a section
of the specimen showing a ruffled, sometimes spiny edge, a detail
that usually is not perserved.
See: Utah Cambrian Explosion
The Fossils of the Burgess Shale - D. E. Briggs, et al.