[1][2] Hoplophorus euphractus was first described in 1837 by Danish paleontologist Peter Wilhelm Lund on the basis of fossilized osteoderms and carapace fragments unearthed in the Upper Pleistocene cave deposits in Lagoa Santa, Minas Gérais, Brazil.

[2] Lund attributed many other fossils to the species over several years, including limb bones,[4] teeth, vertebrae,[5] foot remains, and an incomplete skull.

In 1845, British paleontologist Sir Richard Owen named a new species of Glyptodon, G. ornatus, based on osteoderms recovered from Ensenadan strata in Buenos Aires Province, Argentina.

[10][12] More complete fossil discoveries of Hoplophorus were uncovered from Late Pleistocene-Early Holocene carbonate caves of Lapa do Borges in Minas Gerais were described by Carlos de Paula Caulto in 1947 and 1957.

[2][13][14] These fossils included an individual, associated skeleton with a fragmentary skull, several postcranial elements, a partial carapace, and caudal tube, which further proved the genus’ distinction from Pampean glyptodont species described by Ameghino.

Hoplophorus must have been very similar to other glyptodons such as Neosclerocalyptus, but unlike this one it had a more globular carapace, formed by plates made wrinkled due to the presence of numerous perforations.

[7][2] The tail was protected by a series of bony rings and by a terminal caudal "tube" made up of numerous osteoderms fused together.

[10][2][7] Hoplophorus is a member of the glyptodontinae subfamily, a group of extinct, heavily armored armadillos that existed in the Americas during the Cenozoic.