CHARACTERIZATION OF FEEDING ECOLOGY IN LATE ORDOVICIAN PARACRINOIDS AND RHOMBIFERANS

Echinoderms are a diverse phylum of animals with a wide array of ecological niches and a fossil record dating back to the Early Cambrian. Much of the research on echinoderm feeding ecology has been focused on crinoids. Prior work quantifying crinoid feeding ecology has looked at paleocommunity structure, niche partitioning, and ecomorphospace occupation, but little work has been done on other filter feeding echinoderms, namely the blastozoans, that have a similar ecology to crinoids. In blastozoan echinoderms, some qualitative research has looked at the life mode of different taxa. However, there has not been any work done to quantify the feeding ecology of blastozoan echinoderms to date in terms of niche occupation, niche differentiation, or how similar or different their feeding ecology is to that of crinoids. As a result, a major gap in understanding echinoderm paleoecology is quantifying feeding ecology in blastozoans.

In this study, we developed a framework for characterizing the feeding ecology of blastozoan echinoderms, with particular focus on paracrinoids and rhombiferans. We primarily focused on the Bromide Formation because of its high blastozoan diversity and the fact that there is a prior study on the crinoids from this fauna. However, some additional rhombiferan and paracrinoid taxa were sampled from other faunas of similar ages to increase the sample size. Measurements of ecomorphological characters including thecal height and width, brachiole length, number of brachioles, individual brachiole height and width, and ambulacral width and length were analyzed using multivariate statistical methods to capture paleoecological information such as niche occupation, parameters of niche differentiation, and ecological similarities and differences. We then compared ecological data between different groups of blastozoans, including paracrinoids and rhombiferans, and to data from a prior study of crinoids from the Bromide Formation to evaluate ecological overlap between these groups.

The results of this study paint a more accurate picture of how blastozoan echinoderms interacted with one another, with their environments, and their ecological relationships to other filter feeders, such as crinoids.