INVESTIGATING EVOLUTIONARY DYNAMICS OF PALEOZOIC ECHINODERMS

The Paleozoic was a time that included several evolutionary events, including radiations and mass extinctions. The Great Ordovician Biodiversification Event (GOBE), Late Ordovician Mass Extinctions (LOME), and the end-Devonian extinctions are three such events that shaped evolutionary trajectories. The marine invertebrate fossil record provides a robust platform upon which to test hypotheses related to paleobiogeography, diversity, speciation rate changes, and disparity. Crinoids are dominant in Paleozoic faunas in terms of abundance and diversity, and as such their dynamics have been far more intensely studied than other groups of Paleozoic echinoderms. This study examines the dynamics of non-crinoid echinoderms throughout the early Paleozoic using a mix of biogeographic, morphometric, and evolutionary analyses. The response of early Paleozoic non-crinoid echinoderms are investigated across key evolutionary events, such as the GOBE, LOME, and the end-Devonian extinction.

Biogeographic and stratigraphic data were collected for rhombiferan, diploporan, and blastoid taxa. Biogeographic patterns within the diploporans suggest most dispersal events occurred in the Early to Middle Ordovician and blastoid biogeographic patterns showcase major dispersal and diversification events during the Devonian. Analysis on select diploporan echinoderms indicate dispersal in this group from Baltica into Laurentia included a doubling of body size, but no significant expansion of morphological forms; further analyses will determine if blastoids and rhombiferans show similar patterns. Taxonomic diversity and evolutionary rates will be calculated for rhombiferan, diploporan, and blastoid taxa to begin to assess these groups’ responses across major evolutionary events and how these responses may have differed within and among these groupings of echinoderms. This work is the start of a comprehensive assessment of the diversity, ecology, and biogeography of a diverse Paleozoic clade.