Alternative spelling: Librostoma
Full reference: R. A. Fortey. 1990. Ontogeny, hypostome attachment and trilobite classification. Palaeontology 33(3):529-576
Parent taxon: Trilobita according to M. C. Ebach and K. J. McNamara 2002
See also Fortey 1990 and Hughes 1994
Sister taxa: Aglagalia, Agraulaeva, Aguaraya, Aldonaiidae, Altajaharpes, Amechilus, Amgaspididae, Ampellatocephalina, Anacopodia, Antagmidae, Antatlaeva, Atopidae, Auritamidae, Avoninidae, Batchatiella, Beikedamaspis, Bergerolimbus, Burlingiidae, Changshaniidae, Chinensis, Corynexochida, Crossoura, Curiaspis, Cuyanaspis, Cyclolenzellina, Dalmanites troosti, Deltacare, Devonocoryphe, Edganocare, Elleria, Elleria morani, Ellipsocephaloididae, Ellipsuella, Entomostracites, Erbenochile, Eulomella, Eutrilobita, Fabulaspis, Faciura, Gentilaspis, Gigmpeltis, Goycoia, Harpetida, Helioproetoides, Holocephalinidae, Howelluella, Idiorapha, Ignotogregatidae, Indigestus, Irvingelloides, Ishpella, Isocolidae, Issafenia, Ityophoridae, Jonotus, Juriietella, Kamlacus, Kanfuqingia, Leptopilus, Lichida, Llanoaspididae, Loxopeltis, Lusampa, Mapaniidae, Megalaspidicus, Meneghinella, Metapopristis, Monkaspididae, Moolatrilo, Moretaeva, Moretarva, Namanoiidae, Neochilonorria, Neomalungia, Neotaenicephalus, Odontopleurida, Olenida, Opisthoparia, Orictocara, Otekmaspis, Otenaspella, Paichiashania, Paleoaethia, Parakingaspidoides, Pararania, Peculicephalina, Perissopyge, Phacopida, Piliolites, Pliomerellus, Poculicephalina, Polycyrtaspididae, Prodamesella, Proetida, Proparia, Pseudoacicaudus, Pseudoclelandia, Pseudocrecephalaspina, Pseudosalteria, Pseudosarkia, Pseudotermierella, Pterocephalus, Ptyttstrigis, Punctaspis, Redlichiida, Remopleuridacea, Repinaella, Resseria, Resseropsis, Rochaeva, Sarkiidae, Serksia, Serksioides, Sibiriopeltis, Sphaerocare, Spizharaspis, Stittaspis, Sukhanaspis, Sunaspididae, Suyougouia, Taidonurus, Taplimella, Tazemmourtia, Thymurus, Toxotis, Trapezocephalina, Triarthrella, Trilobus, Tuberaspis, Tuyunaspis, Ulrickaspis, Utiidae, Westergardia, Winsteria, Wuaniidae, Zigzuella
Subtaxa: Asaphida Ptychopariida Trinucleida
Distribution:
• Carboniferous of United States (1: Colorado collection)
• Silurian of Algeria (1), Australia (1), Austria (1), Canada (3: Northwest Territories, Quebec), Czechia (5), Italy (2), Morocco (2), the United Kingdom (4), United States (2: Arkansas, Georgia)
• Uhaku of Belarus (2), Latvia (1), Lithuania (2), Norway (24), the Russian Federation (3), Sweden (20)
• Dobrotivian of Czechia (10), France (8), Morocco (2), Portugal (3), Spain (11)
• Liben of Czechia (13)
• Letna of Czechia (2)
• Whiterockian of Canada (55: Newfoundland, Newfoundland and Labrador, Northwest Territories, Quebec), China (6), Norway (4), United States (89: California, Nevada, New York, Oklahoma, Utah, Vermont)
• Chazyan of Canada (33: Newfoundland and Labrador, Northwest Territories, Ontario, Quebec), United States (67: California, New York, Oklahoma, Tennessee, Vermont)
• Valaste of Sweden (11)
• Hunderum of Sweden (14)
• Langevoja of Sweden (25)
• Whitlandian of the United Kingdom (3)
• Billingen of Estonia (7), Norway (1), the Russian Federation (13), Sweden (28)
• Arenig of Argentina (13), Australia (34), Bolivia (11), Canada (3: Newfoundland and Labrador), China (126), France (7), Greenland (1), Iran (1), Morocco (3), Norway (5), the Russian Federation (2), Spain (1), Sweden (8), the United Kingdom (10), United States (8: Montana, Nevada, New York, North Dakota, Vermont)
• Klabava of Czechia (2), France (3)
• Arenigian of Argentina (55), Canada (2: Northwest Territories), China (43), United States (7: Nevada, Utah)
• Dawan of China (8)
• Ordovician to Silurian of Canada (2: Québec)
• Ordovician of Antarctica (1), Argentina (275), Australia (89), Belarus (4), Belgium (4), Bolivia (13), Canada (291: Alberta, British Columbia, Manitoba, Newfoundland, Newfoundland and Labrador, Northwest Territories, Northwest Terrorities, Nunavut, Nunvait, Ontario, Quebec, Québec, Yukon), China (413), Colombia (2), Czechia (35), Estonia (20), France (29), Greenland (4), Iran (27), Ireland (31), Italy (32), Kazakhstan (23), Kyrgyzstan (2), Latvia (6), Lithuania (16), Mexico (22), Morocco (38), Myanmar (10), the Netherlands (1), New Zealand (1), North Korea (1), Norway (344), Oman (2), Peru (3), Poland (2), Portugal (7), the Russian Federation (138), Saudi Arabia (1), South Korea (5), Spain (31), Sweden (277), Türkiye (5), Ukraine (1), the United Kingdom (294), United States (1293: Alaska, British Columbia, California, Georgia, Idaho, Illinois, Illinois, Iowa, Indiana, Iowa, Iowa/Wisconsin, Kentucky, Maine, Maryland, Michigan, Minnesota, Missouri, Montana, Nevada, New Mexico, New York, North Dakota, Ohio, Oklahoma, Pennsylvania, Pennsylvania and Virginia, Tennessee, Texas, Utah, Vermont, Virginia, Wisconsin, Wyoming), Venezuela (1), Vietnam (1), Åland Islands (1)
• Canadian of Canada (3: Newfoundland, Newfoundland and Labrador, Northwest Territories), United States (3: Maryland, Utah)
• Ibexian of Norway (1), United States (13: California, Nevada)
• Skullrockian of Argentina (1), Canada (26: Alberta, British Columbia, Newfoundland), Greenland (1), United States (43: Nevada, New York, Texas, Utah)
• Taoyuanian of China (62), the Russian Federation (25), South Korea (59), Türkiye (2)
• Cambrian to Ordovician of Argentina (5), Canada (1: Quebec), Norway (1), the Russian Federation (2)
• Cambrian of Antarctica (16), Argentina (22), Australia (102), Canada (290: Alberta, Alberta-British Columbia, Brithish Columbia, British Columbia, New Brunswick, Newfoundland, Newfoundland and Labrador, Northwest Territories, Northwest Territory, Nunavut, Quebec, Yukon, Yukon Territory), China (558), Czechia (14), Denmark (1), France (8), Germany (22), Greenland (29), India (34), Iran (7), Italy (1), Kazakhstan (146), Kyrgyzstan (1), Mexico (5), Mongolia (1), Morocco (6), New Zealand (1), North Korea (1), Norway (6), Poland (2), the Russian Federation (107), South Korea (36), Spain (18), Sweden (11), Türkiye (28), the United Kingdom (11), United States (1189: Alabama, Alaska, Arizona, Arkansas, California, California-Nevada, Colorado, Georgia, Idaho, Idaho/ Utah, Indiana, Massachusetts, Minnesota, Missouri, Montana, Nevada, Nevada and California, Nevada and Utah, New Mexico, New York, Oklahoma, Pennsylvania, South Dakota, Tennessee, Texas, Utah, Vermont, Virginia, Wisconsin, Wyoming, Wyoming-Montana), Vietnam (1)
• Templetonian of Australia (1), United States (3: Nevada)
• Amgan of Czechia (3), Iran (1), Kazakhstan (4), Norway (1), the Russian Federation (5), United States (3: Alaska, Utah)
• Solvan of Canada (41: British Columbia, Newfoundland and Labrador), Czechia (7), Greenland (1), Kazakhstan (1), Norway (1), the Russian Federation (1), Spain (1), United States (91: Nevada, Pennsylvania)
• Waucoban of Canada (1: British Columbia), Greenland (1)
• Caerfai of United States (1: New York)
Total: 7720 collections including 17593 occurrences