EARLY TRIASSIC ECHINOIDS OF THE WESTERN UNITED STATES: THEIR IMPLICATIONS FOR PALEOECOLOGY AND THE HABITABLE ZONE HYPOTHESIS FOLLOWING THE PERMO-TRIASSIC MASS EXTINCTION

Confronted with global climate change and ocean acidification, our collective knowledge of ecosystem response during times of environmental crisis in Earth’s ancient past may provide insights towards combating ecological degradation in modern oceans. Early Triassic marine environments were characterized by oceanic warming due in part to elevated levels of atmospheric CO₂ and periodic intervals of localized anoxia, resulting in an overall restructuring of faunal dominance, distribution, and biodiversity. Re-assembly of ecological communities during the Early Triassic are largely unknown; however, a previous paleoecological study by Tyler Beatty et al. (2008), suggests that post-extinction recovery length was minimized in shallow marine habitable zones. To further expand upon the investigations of Beatty et al., I used Early Triassic echinoids as a case study for understanding paleoecology on the eastern margin of Panthalassa. I hypothesized that amidst the deleterious environmental conditions of the Early Triassic, echinoids thrived within the habitable zone as an abundant member of the Modern Fauna.

Early Triassic echinoids of the western United States appear exclusively within shallow marine shelves, all of which contain evidence of frequent storm activity. Echinoids co-occur with bivalves, brachiopods, gastropods, and other echinoderms, indicating that these habitats were well oxygenated enough to support paleocommunities of considerable diversity. The oceans of the Early Triassic provide only an approximate analogue for modern oceans; however, analysis of Early Triassic ecosystems via quantification of echinoid abundance and paleoecology may help reveal important patterns necessary in understanding the rapidly shifting ecosystems of our modern, warming oceans.