Macrotritopus

Macrotritopus is a poorly known genus of octopuses in the family Octopodidae. As it stands, Macrotritopus contains two valid described species, Macrotritopus defilippi from the NE Atlantic and Mediterranean, and Macrotritopus beatrixi from the Caribbean and SW Atlantic. Two poorly described, unresolved taxa are known only from planktonic hatchlings (Macrotritopus equivocus and M. scorpio), and a further three undescribed Indo-Pacific species may be attributable to this genus.

The genus Macrotritopus was described by Grimpe (1922) for the single planktonic specimen of Octopus gracilis Verill, 1884, the name referring to the very long third arm pair on the paralarvae. Given that O. gracilis Verill, 1884 was a junior homonym of O. gracilis Souleyet, 1852, authors Joubin & Robson (1929) replaced it with Octopus (Macrotritopus) equivocus, with Macrotritopus regarded as a subgenus at that time, these authors also described M. danae. For a time these Macrotritopus species (all known from paralarvae) were misidentified as juveniles of Scaeurgus unicirrhus. Researchers in the late 1970s/early 1980s proved that Macrotritopus paralarvae from the Atlantic grew into the previously described Octopus deflippi Verany, 1851, thus connecting the juveniles with the adults (and moving Octopus deflippi to genus Macrotritopus). Therefore, the type species of Macrotritopus (M. equivocus) is a juvenile, and M. defillipi was the only species where the adult form was known (until the 2018 description of M. beatrixi). The presence of "Macrotritopus larvae" off South Africa and the Indo‑West Pacific from Australia to Hawaii indicates that there may be a number of yet to be described species within this genus.