Nevada’s Sunrise Formation preserves marine fossils from the Early Jurassic, especially the Hettangian to Sinemurian stages. Its fossil record includes ammonites, bivalves, and echinoids, including Plesiechinus hawkinsi. Study of the formation has centered particularly on ammonites, whose importance for dating rock layers has made the Early Sinemurian sequence at New York Canyon in Mineral County especially useful. The formation is significant because its fossils help document marine life and support Jurassic biochronology in the western United States.