Rhynchonellata - Orthida - Eoorthidae
Parent taxon: Plectorthoidea according to J. Hansen and L. E. Holmer 2011
See also Roberts and Jell 1990 and Williams et al. 2000
Sister taxa: Apatoskenidioides, Chilcorthidae, Cremnorthidae, Cyclocoeliidae, Euorthisinidae, Finkelnburgiidae, Giraldiellidae, Lebediorthis, Nanorthidae, Phragmorthidae, Platystrophiidae, Plectorthidae, Ranorthidae, Rhactorthidae, Tasmanorthidae, Wangyuiidae
Subtaxa: Apheoorthina Apheoorthis Austrohedra Brahimorthis Eoorthis Glaphyrorthis Jivinella Ocnerorthis Otusia Pompeckium Robertorthis
Type: Eoorthis
Ecology: stationary epifaunal suspension feeder
Distribution:
• Aluoja of Estonia (1 collection)
• Arenig of China (2), Sweden (5)
• Ordovician of Australia (4), Canada (3: Alberta, Quebec), China (1), Estonia (2), Ireland (1), Norway (2), the Russian Federation (8), South Korea (4), Sweden (3), United States (10: Alaska, Montana, Nevada, North Dakota, Utah)
• Tremadoc of Argentina (6), Bolivia (4), China (12), Colombia (1), the Czech Republic (5), the Russian Federation (4), United States (3: Montana, Utah, Vermont)
• Ibexian of United States (1: Nevada)
• Skullrockian of Greenland (1), United States (1: Utah)
• Amgan of the Czech Republic (1)
• Solvan of Australia (1), the Czech Republic (2)
• Cambrian of Australia (1), the Czech Republic (1), Kazakhstan (2), Morocco (5), Norway (3), the Russian Federation (7), Spain (1), United States (29: Missouri, Montana, Nevada, Oklahoma, Pennsylvania, South Dakota, Texas, Utah, Wisconsin, Wyoming)
Total: 137 collections including 158 occurrences