Petromyzontida - Cephalaspidiformes
Parent taxon: Osteostraci according to R. S. Sansom 2009
See also Janvier 1985 and Voichyshyn 2006
Sister taxa: Aachenaspis, Fieldingaspis, Meelaidaspis, Ohesaareaspis, Tuvaspis, Camptaspis, Tremataspidiformes, Tremataspidida, Benneviaspidiformes, Thyestiida, Waengsjoeaspis, Yvonaspis, Zenaspidida, Ateleaspidiformes, Benneviaspidida
Subtaxa: Cephalaspidiens Cephalaspis Hildenaspis Mimetaspis Pattenaspis
Ecology: fast-moving nektonic carnivore
Distribution:
• Devonian of Canada (10: New Brunswick, Northwest Territories, Nova Scotia, Nunavut, Quebec collections), Germany (2), Norway (8), Svalbard and Jan Mayen (1), Ukraine (11), the United Kingdom (14), United States (2: Wyoming)
• Silurian of Lithuania (1), the United Kingdom (1)
Total: 50 collections including 66 occurrences