What are Kelps and Brown Algae? Kelps and brown algae belong to the group Phaeophyta. Although they photosynthesize like plants and other protists, they use different pigments that give them a distinctive brownish color. The kelps are the largest protists, growing up to 60 meters long, and are well-known for the large underwater “forests” they form along some coastlines. All the phaeophytes are multicellular, even those brown algae that are microscopic. Some questionable fossil brown algae have been found in Precambrian rocks; however, more likely fossil phaeophytes come from Ordovician rocks.
First known fossil occurrence: Ordovician.
Last known fossil occurrence: Quaternary. This group has living relatives.
Fossils through time:
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