[1] The new species was later classified with the name Phoberomys pattersoni in honor of palaeontologist Brian Patterson.

[2] Originally, Phoberomys pattersoni was estimated as being approximately 741 kg based on dimensions of the femur, which at the time made it the largest known species of rodent, living or extinct.

[3] However, these estimates were criticized as being too large by later studies,[4][5][6] which found that Phoberomys had an exceptionally thick femur relative to its body compared to other mammals.

Body mass estimates based on skull length,[4] occipital condyle width,[4] tooth row length,[5][6] and femur length[5] suggest Phoberomys weighed between 150 and 250 kg (330 and 550 lb), making it about the same size as a large antelopes such as greater kudu and waterbuck.

Although Phoberomys pattersoni was considered the largest known rodent at the time of its description, the discovery of a complete skull of Josephoartigasia monesi in 2008 showed this species to be even larger.