Dasypus neogaeus

Dasypus neogaeus Temporal range: Late Miocene (Huayquerian) ~9–6.8 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Cingulata
Family:	Dasypodidae
Genus:	Dasypus
Species:	†D. neogaeus
Binomial name
†Dasypus neogaeus Ameghino, 1891

Dasypus neogaeus is an extinct species of armadillo, belonging to the genus Dasypus, alongside the modern nine-banded armadillo. The only known fossil is a single osteoderm, though it has been lost, that was found in the Late Miocene strata of Argentina.^[1]

Fossils of Dasypus neogaeus were first collected from the Late Miocene “Osiferous Conglomerate” of the Ituzaingo Formation of Parana, Entre Rios Province in northern Argentina by paleontologist Florentino Ameghino.^[1][2] However, some authors recently have stated that the fossils may have come from the Pleistocene.^[3] The fossils consisted only of a single, mobile osteoderm from the dorsal carapace.^[1][2] The osteoderm was then sent to the Bernardino Rivadavia Natural Sciences Argentine Museum in Buenos Aires, where it was described and named Dasypus neogaeus by Ameghino in 1891.^[2][1] Since then, no additional fossils have been assigned to the taxon, although fossils of the same age have been unearthed in other areas of Argentina.^[4][5]

The holotype osteoderm measures only around 13 millimeters long, but indicates a species larger than Dasypus hybridus but smaller than D. novemcinctus.^[1] The osteoderm also differs from that of other species in that it bears more piliferous foramina, 8 in total, on the posterior end than D. novemcinctus.^[2][1][4] Although it only bears 2 physical diagnostic features and is known from very fragmentary fossils, more diagnostic characters could be in the histological anatomy of the osteoderm.^[1]

Based on the taphonomic and environmental information provided by the “Osiferous Conglomerate” the holotype was found in, D. neogaeus lived in areas with gallery forests near water.^[1] This is contrary to the modern Dasypus species, which live in grasslands, suggesting that Dasypus and other smaller armadillos recently underwent an ecological change.^[6][1]

Fossils have only been unearthed from the Ituzaingó Formation of Entre Rios, Argentina, which preserves vast tidal flats similar to those in the modern day Amazon and a warm climate.^[7] Large, herbivorous notoungulate mammals in the Ituzaingó Formation were widespread, including the toxodontids Xotodon and Adinotherium,^[8] and litopterns such as Brachytherium, Cullinia, Diadiaphorus, Neobrachytherium, Oxyodontherium, Paranauchenia, Promacrauchenia, Proterotherium and Scalabrinitherium.^[9] Large, armored glyptodonts like Palaehoplophorus, Eleutherocercus, and Plohophorus^[1] lived in the area as well as other cingulates like the pampatheres Kraglievichia^[1] and Scirrotherium.^[10] Carnivores included the phorusrhacids Devincenzia and Andalgalornis^[11] and sparassodonts,^[12] with giant crocodilians like Gryposuchus and Mourasuchus in the freshwater.^[13] Bamboos, coconut palms, and other palms were prevalent.^[14]