A vertebrate fauna from the Middle Devonian Yahatinda Formation of southwestern Canada

The Yahatinda Formation of southern Alberta and British Columbia consists o f a series of channels cut into lower Paleozoic rocks and represents deposi tion in marine to littoral environments across a major regional unconformit y. The age of the beds is late Givetian based on spore assemblages and plan t macrofossils. A vertebrate fauna from the formation is described here for the first time and includes Heterostraci (two new species of tuberculated pteraspidids), Placodermi (an antiarch and the arthrodire Holonema together with indeterminate arthrodires), Osteolepiformes, and Porolepiformes. This -report documents for the first time that pteraspidids, considered to be or ganisms characteristic of the Lower Devonian elsewhere, lingered:to the end of the Middle Devonian in western North America. This fauna is similar to others occurring further south in the western United States.