Speakers: Richard Lund and Eileen Grogan
“Fossil Fishes of Bear Gulch of Montana.”

The Bear Gulch Limestone, a Montana Mississippian lagerstätte, has produced an array of fossils of virtually unparalleled quality and content. The deposit preserves what was a small tropical marine bay, with major taxonomic groups of fish represented. Yet, many of the 150+ recovered Bear Gulch species are entirely new. The abundance and diversity of Osteichthyes and Chondrichthyes contrast with today’s marine environments. The Chondrichthyes were much more adaptively diverse. Their range of diversity precludes many from classification as either Elasmobranchii (sharks, skates and rays) or Holocephali (chimaeroids), as modern fish are. Within Osteichthyes, Actinopterygii and Sarcopterygii differ principally in fine functional and morphological parameters. Some select taxa are more highly derived than otherwise expected for this age. Information relating to prey items, ontogenetic and sexual variation, and reproductive history are available for many. Laboratory and field data allows analyses of the fish habitats and community structure across the bay. They reveal Mississippian fish had well-defined ecological guilds based upon feeding, swimming, reproductive and life history distinctions. We know this only because the Bear Gulch lagerstätte provides this rare glimpse of the scope of evolutionary radiation accomplished within 37-53 million years after the end-Devonian mass extinction.