The deep sea isopods are a very charismatic and well-known bunch of crustaceans. Not everybody has an in-depth knowledge of em, but those that do call it Bathynomus and have since 1879, but that was potentially subject to change at one point.
In January of 1989 Robert Wieder and Rodney Feldmann described a fossil giant isopod from Washington, under the genus Palaega. Palaega was established in 1870, and has been applied to fossil isopods spanning as far back as the Triassic. The specimen described, part of Palaega, was so similar to extant Bathynomus that it was argued that the two genera should be synonymized. There is a historical precedent for this idea – papers in 1935, 1953, and 1980 all noted great similarity between the two, but they all refrained from synonymizing since the fossils they were describing were not always complete.
Word was sent to the ICZN a few months later, and the issue was discussed for roughly three years.
The main issue with merging the two, and the reason why this merging was voted against, was the potential dubious nature of Palaega. Palaega has been suggested to be a “form genus”; a group of species with similar morphology but no confirmed phylogenetic relationship. Diagnostic traits of what would be considered Palaega proper have been determined, but nobody has applied these and sorted out the genus yet. Bathynomus itself has been reported in fossils, and shifting some members of Palaega (such as P. goedertorum, which started this debate) into Bathynomus has also been proposed. At the moment it appears that Bathynomus may be an old genus, appearing in the Eocene or Oligocene. Its relationship to, and the general relationships of Palaega aren’t well understood at this time, more research must be done.
Bathynomus is still used to refer to the extant giant isopods, and Palaega to the fossil ones; several new species have been named since this debacle started
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