A detailed comparative morphology of the following 21 species is made: 1) Strombidae: Strombus pugilis (Brazil), S. alatus (Florida, USA), S. gracilior (form Panama, Pacific coast), Eustrombus goliath (Brazil), E. gigas (Caribbean), Aliger costatus, A. gallus (northeastern Brazil), Tricornis raninus (Caribbean); Conomurex luhuanus, Canarium urceus, Lambis lambis, Terebellum terebellum (all Australia), Tibia insulaechorab (Pakistan); 2) Struthiolariidae: Struthiolaria papulosa (New Zealand), Tylospira scutulata (Australia); 3) Aporrhaidae: Cuphosolenus serresianus new comb., Aporrhais occidentalis and A. pespelicani (North Atlantic and Europe); 4) Xenophoridae: Onustus caribaeus and Xenophora conchyliophora (West Atlantic) and O. indicus (Australia). The three former families are usually considered members of the superfamily Stromboidea, while the Xenophoridae are included in their own superfamily Xenophoroidea. A phylogenetic (cladistic) analysis is undertaken, based on 102 characters (255 states); with some basal Caenogastropoda as the main outgroup. A single most parsimonious tree was obtained (length: 209, CI: 74; RI: 86) as follows: ((T. scutulata-S. papulosa) (C. serresianus ((A. occidentalis-A. pespelicani)((O. caribaeus-O. indicus)-X. conchyliophora)(T. terebellum (C. urceus (C. luhuanus (T. raninus (L. lambis (S. pugilis-S. alatus-S. gracilior)((E. goliath-E. gigas) (A. costatus-A. gallus))))))))))). According to this analysis, Stromboidea (including Xenophoridae) is a monophyletic superfamily supported by 42 synapomorphies, Xenophoridae and Strombidae are monophyletic, as well as Strombus, Aliger and Eustrombus are monophyletic genera; whereas Aporrhaidae and Aporrhais are paraphyletic taxa; the Xenophoridae are the sister taxon of the Strombidae. Lambis lambis is represented in a branch within species currently included in Strombus, thus some genera were revalidated (Eustrombus and Aliger) and subgenera require elevation to genera (Strombus s.s., Tricornis, Conomurex, Canarium).
