[2] It was the first Bathynomus species ever documented and was described in 1879 by French zoologist Alphonse Milne Edwards after the isopod was found in fishermen's nets off the coast of the Dry Tortugas in the Gulf of Mexico.

[4][5] The unusually large size of Bathynomus has been attributed to an effect called deep-sea gigantism, where invertebrates living in cold deep waters tend to grow larger and have longer lifespans.

[6][7] Like most crustaceans, the body of Bathynomus giganteus is divided into three distinct regions; a head (cephalon), a thorax, and an abdomen (pleon).

Mature females develop a pouch known as a marsupium, where the eggs are stored until the young are ready to emerge as miniatures of the adults, known as manca, completely bypassing a larval stage.

They feed on the remains of dead marine organisms that sink to the ocean floor, helping to recycle nutrients back into the ecosystem.