Biology:Enchoteuthis

Enchoteuthis (meaning "spear squid") is an extinct genus of large enchoteuthine cephalopod that lived during the Cretaceous. Although it and its relative Tusoteuthis are often compared to squid, both are now thought to be more closely related to modern octopuses. Examination of gladius remains initially yielded an estimated mantle length of about 2 m (6 ft 7 in) based on one specimen once described as Tusoteuthis longa, which is close to or equal to that of the modern giant squid, although reclassification of this genus as a muensterelloid results in a longer total length, about 3 m (10 ft). Three species are currently recognized as valid: E. melanae, E. tonii, and E. cobbani.

Etymology

The generic name Enchoteuthis is derived from the Greek enchos ("spear") and teuthis ("squid"). The specific name melanae honors Melanie Bonner, who discovered the holotype. E. cobbani is named after William Cobban.

Distribution

E. melanae and E. cobbani are both known from the Late Cretaceous Western Interior Seaway of North America, with specimens found in Kansas, Wyoming, South Dakota, North Dakota, and Manitoba. E. tonii is known from the Early Cretaceous Eromanga Seaway of Australia. An additional unnamed species is known from the Late Cretaceous Paleo-Pacific Ocean of North America, specifically British Columbia and Alaska.

Taxonomy and Phylogeny

In analysis of Enchoteuthis and related fossil coleoid cephalopods, Larson erected the family Enchoteuthididae for Enchoteuthis, Tusoteuthis, Niobrarateuthis and Kansasteuthis. However Kansasteuthis has since been deemed a subjective junior synonym of Enchoteuthis while Tusoteuthis is considered a nomen dubium.

Muensterelloids have traditionally been identified as being closely related to teudopseids, a clade that includes the majority of known gladius-bearing Mesozoic cephalopods. In 1990 Engeser for the first time considered the relationship of the Muensterelloidea to the Octopoda, which includes all modern cirrate and incirrate octopus. Fuchs et al. (2020) found Muensterelloids to be sister taxa to the Palaeololiginidae. The very same analysis finds Muensterelloids, which have never been found to be paraphyletic, to consist of two main clades, the Patelloctopodidae and the ‘Muensterella–Enchoteuthidae clade’. The unusual morphology of the gladius in Patelloctopus ilgi links the morphology seen in teudopseids like Muensterella and crown cirrates and incirrates. It is possible that the patelloctopodid clade includes the last common ancestor of cirrate and incirrate octopods, whereas the "Muensterella-Enchoteuthidae" clade likely became extinct during the Late Cretaceous. Presumably, these two clades split in the middle-late Toarcian, which would make it congruent with the minimum divergence date calculated by Tanner et al. (2017) using molecular clock analysis.

The results of the 2020 analysis show Enchoteuthis as the most derived member of the "Muensterella-Enchoteuthidae" clade:

Vampyromorphida	Teudopsis acuta       Palaeololigo albersdoerferi   Muensterelloidea   Celaenoteuthis incerta       Engeseriteuthis arcuatus         Listroteuthis conica       Muensterella scutellaris       Muensterella spinosa       Muensterella jillae       Muensterella sp.   Enchoteuthidae   Niobrarateuthis bonneri       Enchoteuthis melanae       Enchoteuthis cobbani     Enchoteuthis tonii                       Tyrionella fauseri       Etchesia martilli       Muensterellina johnjagti     Patelloctopodidae   Pearceiteuthis buyi     Patelloctopus ilgi     Palaeoctopodidae     Keuppia hyperbolaris     Keuppia levante       Palaeoctopus newboldi     Styletoctopus annae   (Relationship with Patelloctopodidae is assumed only)

See also

• Tusoteuthis
• Muensterella
• Cephalopod size

References

Wikidata ☰ Q106462802 entry