The Yahatinda Formation of southern Alberta and British Columbia consists of a series of channels cut into lower Paleozoic rocks and represents deposition in marine to littoral environments across a major regional unconformity. The age of the beds is late Givetian based on spore assemblages and plant 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 organisms 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.
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