Discussion of Phylogenetic Relationships
The systematics of the myopsid squid family Loliginidae have long been in disorder. In addition to many problems with differentiation of species, loliginid systematics have been hampered throughout the last several decades of the 20th Century by the presence of two systems of generic-level classification. The differences between these two systems primarily involved a question of the importance of gladius structure at the generic level. Both systems have been used widely in the scientific literature, although many authors consistently qualified their use by stating that the family was badly in need of revision based upon a worldwide review.
Three separate morphological revisions have been completed (Natsukari, 1984b; Brakoniecki, 1986; Alexeyev, 1991); all concluded that a correct generic-level classification of the family is radically different from either of the previous classifications. Unfortunately, these new classifications also differed substantially from each other, were presented in unpublished dissertations and not widely disseminated, and none has gained full acceptance.
Obviously, the existence of five contrasting systems of classification can cause hopeless confusion to researchers studing these squids, in addition to obfuscating real relationships among the species. Species groupings into subgenera and genera have been based only on similarity. In a workshop publication, Vecchione et al. (1998), recognized six genera. Four of the genera are divided into subgenera: Lolliguncula (Lolliguncula and Loliolopsis); Uroteuthis (Uroteuthis and Photololigo); Loliolus (Loliolus and Nipponololigo); Loligo (Loligo and Alloteuthis). The generic affinities of several species were unresolved.
A follow-up workshop consensus on generic and sub-generic taxonomy of the family was published by Vecchione et al. (2005), based primarily on the phylogenetic research of Anderson (1996; 2000a; 2000b) and Alexeyev (1989; 1991). Both of those authors built upon the previous workshop proceedings. The most noteworthy differences in Vecchione et al. (2005) from the classification of Vecchione et al. (1998) include the following: (1) removal of mercatoris from Lolliguncula based primarily on gladius characters, DNA sequence data and biogeography, and recognition of Afrololigo Brakoniecki as a valid genus for this species; (2) elevation of Alloteuthis Wülker from sub-generic to full generic status based on gladius structure and DNA sequence data; (3) removal of American species from the genus Loligo because DNA sequence analyses indicate that Loligo sensu Vecchione et al. (1998) is probably paraphyletic. The generic name with priority for the American species is Doryteuthis Naef. This genus further comprises two natural subgroups based on differences in gladius and hectocotylus structure; these subgroups are considered here to be the subgenera Doryteuthis Naef and Amerigo Brakoniecki. Doryteuthis sanpaulensis does not belong in either of these subgenera and is therefore considered to be the sole recognized species in an undescribed subgenus; (4) removal of bleekeri from Loligo and recognition of Heterololigo Natsukari as a valid genus based on DNA sequence analysis; (5) removal of noctiluca from subgenus Uroteuthis of genus Uroteuthis and recognition of Aestuariolus Alexeyev as a valid monotypic subgenus of Uroteuthis primarily because of differences in photophore structure from the rest of the genus.
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