Parent taxon: Protorthida according to M. Rubel 2011
See also Benedetto 2003, Hansen and Holmer 2011 and Williams et al. 2000
Sister taxon: Protorthoidea
Subtaxa: Skenidiidae
Ecology: stationary low-level epifaunal suspension feeder
Distribution:
• Givetian of France (5 collections)
• Devonian of Australia (5), Canada (30: British Columbia, Northwest Territories, Nunavut, Yukon, Yukon Territory), China (1), the Czech Republic (7), Italy (1), Morocco (2), Poland (8), Ukraine (4), United States (19: Iowa, Nevada, New Mexico, New York, Tennessee)
• Whitwellian of Canada (4: Northwest Territories)
• Jaani of Estonia (7), Lithuania (4)
• Niagaran of Canada (2: Québec)
• Silurian to Devonian of Poland (1), United States (1: Oklahoma)
• Silurian of Australia (3), Belarus (3), Canada (24: New Brunswick, Northwest Territories, Nunavut, Quebec, Québec, Yukon, Yukon Territory), China (5), the Czech Republic (6), Estonia (34), Iran (1), Latvia (1), Lithuania (32), Mexico (1), Norway (24), the Russian Federation (1), Sweden (6), Ukraine (1), the United Kingdom (97), United States (47: California, Illinois, Indiana, Iowa, Missouri, Nevada, New York, Oklahoma, Tennessee, Wisconsin), Venezuela (1)
• Whiterockian of United States (4: Nevada)
• Chazyan of Canada (1: Northwest Territories), United States (1: Alabama)
• Dawan of China (1)
• Arenig of Argentina (2), China (3), the United Kingdom (5)
• Arenigian of Argentina (4)
• Ordovician to Silurian of Norway (1)
• Ordovician of Australia (4), Belgium (9), Canada (12: Northwest Territories, Nunavut, Ontario, Quebec, Québec), China (29), Estonia (11), Ireland (9), Italy (1), Kazakhstan (4), Latvia (1), Lithuania (5), Myanmar (1), Norway (16), the Russian Federation (2), Sweden (5), Turkey (1), the United Kingdom (56), United States (65: Alaska, California, Illinois, Iowa, Maine, Minnesota, Nevada, Oklahoma, Pennsylvania, Tennessee, Virginia, Wisconsin)
Total: 641 collections including 672 occurrences