Panochthus

Panochthus is an extinct genus of glyptodont, which lived in the Gran Chaco-Pampean region of Argentina (Lujan, Yupoí and Agua Blanca Formations), Brazil (Jandaíra Formation), Bolivia (Tarija and Ñuapua Formations), Paraguay and Uruguay (Sopas and Dolores Formations) during the Pleistocene epoch. The first specimen of Panochthus consisted of two carapace (shell) fragments, now lost, recovered from Buenos Aires. In 1845, the fragments were referred by Sir Richard Owen to the genus Glyptodon. In 1864, working from more complete remains, Karl Hermann Konrad Burmeister erected Panochthus as a subgenus. Three years later, he elevated it to the rank of genus. The species named by Owen, now P. tuberculatus, stands as the type species, though many others have since been named.

The internal systematics of Panochthus have long been debated. At least twenty species have been named. While some have been reclassified, rendered invalid, or synonymised with existing species, at least nine remain valid. Mitochondrial DNA analyses suggest that Panochthus, like all other glyptodonts, is part of the armadillo family Chlamyphoridae. In 2022, glyptodonts were divided into two main clades: "traditional glyptodontines", and the "Austral clade"; Panochthus is part of the latter, and specifically the tribe Hoplophorini, which also includes Hoplophorus (and possibly Propanochthus, although that may be a species of Panochthus).

Panochthus was generally a large glyptodont, though body size varied between species. The biggest skulls known from the genus have been assigned to P. tuberculatus, measuring 394–442 mm (15.5–17.4 in), while the smallest, that of P. frenzelianus, instead measured 330 mm (13 in). As a genus, Panochthus is characterised by having a skull far deeper than it is long, a downturned nasal region, and three-cusped, molar-like teeth. In some species, the back of the orbit (eye socket) was encircled by a so-called postorbital bar, though this was not true for others. The armour of Panochthus, as in other glyptodonts, consisted of four primary structures: the cephalic shield, which topped the head; the dorsal carapace, which covered the body; the caudal rings, which encircled the base of the tail; and the caudal tube, a rigid mass which covered the last half or so of the tail. In P. intermedius, the caudal tube bears large depressions similar to those seen in Doedicurus, suggesting the presence of conical spines.