Alternative spelling: Thecostomata
Parent taxon: Opisthobranchia according to J. A. Todd 2001
See also Beesley 1998, Harris and Palmer 1947, Sepkoski 2002 and Squires 1989
Sister taxa: Acanthotrophia, Acochlidea, Buscotypus, Canepina, Cephalaspida, Cephalaspidea, Cylindrobullinoidea, Floribella, Gymnosomata, Heteroptygmatis, Heterostrophia, Lutima, Mariottia, Mistostigma, Nicosiaella, Notaspidea, Paronaella, Pseudofusia, Reticulacella, Rhodopemorpha, Scorbinidola, Tectibranchia, Umbraculomorpha
Subtaxa: Bovicornu Bucanoides Camptoceratops Cavoliniidae Cheilospicata Cymbuliidae Desmopteridae Euchilotheca Falsostyliola Gamopleura Limacinidae Lomia Loxobidens Paraclididae Peracle Plotophysops Skaptotion Sphaerocina Thecopsella Tibiella
Ecology: nektonic carnivore
Distribution:
• Quaternary of Costa Rica (4 collections), Greece (1), Italy (1), Japan (1), Mayotte (6), Panama (1), United States (6: California, Louisiana)
• Pliocene to Pleistocene of Jamaica (1)
• Pliocene of Belgium (2), Chile (3), Costa Rica (6), the Dominican Republic (10), Greece (1), Haiti (2), Holy See (Vatican City State) (1), Indonesia (1), Italy (2), Jamaica (6), Japan (1), Panama (16), Portugal (1), Spain (3)
• Miocene of Australia (1), Austria (1), Belgium (1), Cyprus (2), Denmark (1), the Dominican Republic (20), France (24), Germany (33), Greece (1), Grenada (17), Haiti (1), Italy (3), Japan (1), Malta (1), the Netherlands (2), New Zealand (2), Panama (4), Slovakia (2), Trinidad and Tobago (1), United States (7: Florida, Washington)
• Oligocene of France (12), Japan (3), Panama (3), Romania (1), the Russian Federation (1), Trinidad and Tobago (1), United States (11: Mississippi, Washington)
• Eocene to Oligocene of United States (1: Washington)
• Eocene of Canada (1: Nova Scotia), France (9), New Zealand (2), Pakistan (4), the United Kingdom (3), United States (22: Alabama, Mississippi, Oregon, Texas, Washington)
• Paleocene of United States (1: Texas)
Total: 276 collections including 752 occurrences