Trilobita - Ptychopariida - Marjumiidae
Synonym: Coosellidae Palmer 1954
Parent taxon: Ptychopariida according to J. C. Lamsdell and P. A. Selden 2015
See also Adrain 2011, Bruton and Harper 2000, Jell and Adrain 2002 and Whittington et al. 1997
Sister taxa: Acrocephalitidae, Alokistocaridae, Amphorella, Atratebiinae, Bifodina, Bolaspididae, Bulnibarbi, Bvalbardites, Catillicephalidae, Chondrastaulina, Chuangiformis, Cliffiidae, Conococheaquea, Conocoryphidae, Conokephalinidae, Crepicephalidae, Diceratocephalidae, Elviniidae, Harpina, Indiligens, Kazelina, Kingstoniidae, Kirengelia, Lisaniidae, Lonchocephalidae, Lorenzellidae, Meniscocorphye, Menomoniidae, Neoanomocerella, Norwoodiidae, Olenina, Papyriaspididae, Phylacteridae, Plethopeltidae, Proasaphiscidae, Propeltura, Ptychopariidae, Ptychopariina, Ptychoparoides, Raymondinidae, Shumardiidae, Solenopleuracea, Solenopleuridae, Tricrepicephalidae, Xianquianaspis, Yuehsieszella
Subtaxa: Anemocephalops Coosella Crepichilella Glyphopeltis Holmdalia Ithyektyphus Lecanopleura Modocia Nasocephalus Nericella Nericia Pearylandia Petruninaspis Schyilaspis Shickshockia Syspacheilus
Ecology: fast-moving low-level epifaunal carnivore
Distribution:
• Cambrian of Canada (19: British Columbia, Newfoundland, Newfoundland and Labrador, Northwest Territories, Yukon collections), China (1), Greenland (13), the Russian Federation (4), United States (128: Alaska, Georgia, Idaho/ Utah, Nevada, Pennsylvania, South Dakota, Texas, Utah, Vermont, Wisconsin, Wyoming)
Total: 165 collections including 231 occurrences