Modern epibionts foul, or encrust, host organisms. Ancient epibionts are informative because they are fossilized in life position, preserving interactions between epibionts and hosts. Devonian brachiopods were collected and examined for epibionts from the limestone Solon Member of the Cedar Valley Formation at Robins Quarry near Robins, IA and the shale Lime Creek Formation at the Rockford Fossil Preserve near Rockford , IA. Brachiopods found in the Solon Member consisted mainly of atripides and spiriferides . Twenty percent of individuals in the upper Solon sample were encrusted, compared to 40.0% of individuals in the lower Solon sample, with the latter having a lower average of individual epibionts per host. The Lime Creek Formation contained more diverse taxa than the Solon Member with 48.8% encrusted individuals and an average number of epibionts per host similar to the Solon samples. Solon Member samples contained abundant Spirorbis and bryozoan encrusters, but Lime Creek Formation brachiopods were mostly encrusted by rugose corals and enigmatic attachment scars as well as Spirorbis . In all samples, over 50% of encrusted specimens contained Spirorbis with other epibionts , often other Spirorbis . In all samples, brachiopods with the highest encrustation rates have fine ribbing and hosts with the coarsest ribbing have low encrustation rates. Within the Solon Member, although the taxa are similar in both samples, the dynamics of epibiosis are different in each ecosystem and require more study. The differences between the Solon Member and the Lime Creek Formation are likely due to differences in time, taxa, and/or sedimentary environment.
Amelinda Webb, ’06 Grand Island , NE
Majors: Biology and Environmental Studies
Sponsor: Christie Schneider