ring in addition to the 8–9 complete caudal rings and caudal tube. In both genera, each caudal ring is composed by two or three transverse rows of ankylosed osteoderms, where the distalmost row of osteoderms shows a more or less developed conical morphology. In Glyptotherium, in some specimens (e.g., AMNH 95,737) a low number of conical osteoderms (generally two). This is different from Glyptodon, in which most osteoderms of the distal row (up to 12) present a clear conical morphology. The terminal caudal tube is shorter in Glyptodon. In Glyptotherium, the terminal tube is composed of 2–3 ankylosed rings, whereas in Glyptodon, it has only two ankylosed rings. In Glyptotherium, this caudal tube represents ca. 20% of the total length of the caudal armor, whereas in Glyptodon, this structure represents 13% of the total length. Paleobiology Feeding and diet Glyptotherium was mainly a grazer, but also had a mixed diet of C3 and C4 plants based on isotope analyses of dental specimens recovered from the Late Pleistocene Cedral locality in San Luis Potosí, México. The locality preserves C4 plants from the families Poacea, Amaranthacea and Quenopodiacea, meaning that they were possible food sources for Glyptotherium. Cedral specifically was an area with hot springs and open grasslands next to them, suggesting that Glyptotherium’s fed in grasslands nearby water sources, like the feeding habits of modern Capybaras. Additional isotopic analysis of Glyptotherium and the giant ground sloth Eremotherium found the two to have similar isotopic levels to the extant amphibious Hippopotamous, indicating that they were semi-aquatic herbivores that fed on aquatic plants. Additional studies of dental specimens from eastern Brazil suggest that the Glyptotherium were grazers in moist, lowland tropical to subtropical habitats along rivers or water sources, supporting the semi-aquatic Glyptotherium hypothesis. Additional isotopic evidence from Brazil suggests that fruits were also part of Glyptotherium’s diets, though only around 20%. Glyptotherium and all other glyptodonts had hypsodont teeth, high-crowned teeth with rough, flat surfaces adapted for grinding and crushing, that were adapted to break down gritty, fibrous material like grasses. This diet for Glyptotherium contrasts with those surmised for their relatives Pampatheres, which have been considered insectivores or grazers. Like most other xenarthrans, glyptodonts had lower energy requirements than most other mammals. They could survive with lower intake rates than other herbivores with similar mass. Eyesight Rod monochromacy is a rare condition characterized by the absence of cone photoreceptor cells in