REEVALUATING REEFAL RECOVERY: EVIDENCE FOR ROBUST EARLY JURASSIC CORAL POPULATIONS IN NORTH AMERICA

During the Triassic as scleractinian coral diversity and complexity increased corals became the primary framework builder of reefs. The end-Triassic mass extinction resulted in a complete collapse of once prospering coral reef ecosystems. Compared to other marine invertebrate fauna, such as bivalves, corals were particularly slow in recovering from the mass extinction. It took nearly all of the Early Jurassic for coral species diversity to return to pre-extinction levels. Prior research has concentrated on earliest Jurassic corals from the Tethys region, including Asia, central Europe, and Morocco. Reports initially indicated that Early Jurassic coral development in North America was absent, leading to the conclusion that the recovery in eastern Panthalassa was delayed. For the largest part of the 20^th century sparse reports of Early Jurassic North American corals went unnoticed. However, recent investigations support a potentially robust Early Jurassic coral record in the Americas. Interest in finding the earliest post-extinction fossil corals and understanding their slow evolutionary path led to renewed investigations of purported coral occurrences in North America. Early Jurassic coral localities have since been identified in Mexico, Nevada, Canada, and Alaska, indicating a stronger population of post-extinction Panthalassan corals than previously thought. Relative and absolute dating techniques revealed Hettangian to Toarcian ages for the North American corals. Surviving corals of the Hettangian are all simple solitary forms. By the end of their recovery in the Toarcian, corals were more diverse and complex and were again building reefs.