The class Notopharyngea, formerly known as the BaSk clade includes two orders of free-living anaerobic metamonads. It was identified by phylogenomic analyses as a deeply branching sister group to the Fornicata, and recently the rest of Metamonada. The extreme mitochondrial reduction observed within this free-living anaerobic protistan clade demonstrates that mitochondrial functions may be completely lost even in free-living organisms, not only parasites.