COMPLEX INTERACTION BETWEEN CLIMATE AND PATTERNS OF PALEOZOIC ECHINODERM EVOLUTION

Crinoids and blastoids reached an apex in generic richness and abundance during the Mississippian. Although the causes of the Mississippian echinoderm explosion are probably multifaceted, climatic events in the Devonian likely played a major role. Crinoid and blastoid generic richness reached a peak in the Early Devonian reflecting the success of the camerate-dominated Middle Paleozoic Crinoid Macroevolutionary Fauna during an interval of widespread reefal facies which developed in greenhouse climate conditions. Throughout most of the Devonian, echinoderm diversity paralleled the reefal diversity, which paralleled patterns of low latitude sea surface temperature. This pattern changed after Late Devonian extinction events which are associated with the transition from the Devonian greenhouse climate to icehouse climate conditions. Famennian echinoderm communities are dominated by cladid crinoids and more closely resemble Late Paleozoic rather than Middle Paleozoic Crinoid Macroevolutionary Faunas. Crinoid diversity shows strong correlation with modeled values of atmospheric CO₂, but the interactions between CO₂ and diversity exhibit radically different patterns in different clades. Camerate crinoids show strong correlation with climate in the icehouse climate conditions of the Mississippian, but none in the earlier greenhouse climates prevalent in the Devonian. Cladid crinoids show strong correlation between CO₂ and diversity in both greenhouse and icehouse conditions. Flexible crinoids show no correlation between diversity and CO₂. Crinoid communities were able to be successful both in the Lower Devonian greenhouse world and in the Mississippian icehouse world because different clades were able to adapt to changing climates and the demise of reef ecosystems and flourish. These results have potential significance in modern conservation biology because the crinoid clades are only subtly different in large scale population biology, but exhibit radically different responses to long term climate change.