Trilobite and Algae Fossils Association from Utah

Description: The first fossils of multicellular green algae appear in the Cambrian strata of the early Paleozoic Era. Yuknessia as shown here was a thin, frond-like green, carbonaceous algae resembling modern kelp. Complete algal fossils, identified as Yuknessia simplex and Margaretia dorus have also been found in the Burgess shale of Canada; both genera have been classified as Chlorophytes, a distinct branch of green algae from the Streptophytes that eventually gave rise to the land plants. This taxon has not been well studied.

Together with filamentous cyanobacteria (commonly called blue-green algae), algae like Yuknessia built large reef systems that not only supported Cambrian marine life, but photosynthetically augmented atmospheric oxygen levels thus further driving the amazing eukaryotic diversification known as the Cambrian Explosion.

The reverse shows an example of the trilobite Elrathia. What makes this even more rare is the fact a section of the right pleural lobe is missing, the result of the trilobite’s being bitten, presumably by an Anomalocaris. Interestingly, these bites are typically found on the right side of the trilobite, indicating some preferred attack mode by the terror of the Cambrian.

Reference: The Fossils of the Burgess Shale by D. E. Briggs, et al.