Search

We describe several proterotheriid remains from the Andalhuala and the Corral Quemado formations (Villavil-Quillay and Santa María basins, Catamarca Province) and the Andalhuala Formation (Santa María Basin at Encalilla, Tucumán Province), Argentina. Neobrachytherium intermedium distinguishes from N. morenoi by the presence of lophoid metaconules in upper molars and astragalus with fusiform attachment for the tibioastragalar ligament, while N. morenoi presents bunoid metaconules and astragalus with ectal facet slightly projected laterally without attachment for the tibioastragalar ligament. ?Proterotherium simplicidens is considered junior synonym of N. intermedium. N. intermedium is circumscribed to levels ca. 6.02 Ma in the Santa María Basin (extendable to ca. 6.88 Ma), to ca. 3.66 Ma in Puerta de Corral Quemado. N. morenoi is restricted to levels above ca. 6.02 to below ca. 4.85 Ma in the Santa María Basin. While other species of Neobrachytherium (i.e. N. ullumense and N. ameghinoi) are distributed in Argentina and Uruguay, N. intermedium and N. morenoi only have records in the late Neogene of northwestern Argentina. These distributions align with earlier hypotheses regarding a regional ecological distinction between the western and eastern regions in the northern half of Argentina during the late Neogene while also fitting the paleophytogeographic provinces (Neotropical and Proto-Spinal). [ABSTRACT FROM AUTHOR]

Glyptodonts were giant (some of them up to ~2400 kg), heavily armoured relatives of living armadillos, which became extinct during the Late Pleistocene/early Holocene alongside much of the South American megafauna. Although glyptodonts were an important component of Cenozoic South American faunas, their early evolution and phylogenetic affinities within the order Cingulata (armoured New World placental mammals) remain controversial. In this study, we used hybridization enrichment and high-throughput sequencing to obtain a partial mitochondrial genome from Doedicurus sp., the largest (1.5 m tall, and 4 m long) and one of the last surviving glyptodonts. Our molecular phylogenetic analyses revealed that glyptodonts fall within the diversity of living armadillos. Reanalysis of morphological data using a molecular 'backbone constraint' revealed several morphological characters that supported a close relationship between glyptodonts and the tiny extant fairy armadillos (Chlamyphorinae). This is surprising as these taxa are among the most derived cingulates: glyptodonts were generally large-bodied and heavily armoured, while the fairy armadillos are tiny (~9-17 cm) and adapted for burrowing. Calibration of our phylogeny with the first appearance of glyptodonts in the Eocene resulted in a more precise timeline for xenarthran evolution. The osteological novelties of glyptodonts and their specialization for grazing appear to have evolved rapidly during the Late Eocene to Early Miocene, coincident with global temperature decreases and a shift from wet closed forest towards drier open woodland and grassland across much of South America. This environmental change may have driven the evolution of glyptodonts, culminating in the bizarre giant forms of the Pleistocene. [ABSTRACT FROM AUTHOR]

Late Pleistocene outcrops exposed in Buenos Aires province, Argentina, represent one of the most informative sources about the paleoecology of South American megafauna. However, there are no records of an accurately dated carnivore–herbivore taphocenosis. This paper presents preliminary results of a recent excavation at the margins of the Salado River, on sediments attributed to the Luján Formation (Late Pleistocene–Early Holocene). The fossiliferous strata consist of greenish brown sandy-clays deposited in a small paleopond environment that was filled by fluvial sediments, exhibiting abundant organic matter, gypsum and carbonate concretions. Fieldwork yielded an association of extinct large-sized mammals that include the horse Hippidion principale, the saber-tooth cat Smilodon populator (at least one adult and one juvenile associated specimen), a giant ground sloth Megatherium americanum, and the glyptodont Doedicurus clavicaudatus. Four 14C dates were performed on organic matter (12,100 ± 100 14C BP), a femur of S. populator (13,400 ± 200 14C BP), and a cervical vertebra of Hippidion principale (12,860 ± 120 14C BP), and a pelvis of D. clavicaudatus (12,380 ± 190 14C BP) situating the site within 12,500 and 13,500 years, approximately. Remarkably, some of the recovered specimens exhibit conspicuous bone modifications (furrows, pits, punctures, striations and crenulated margins) attributed to the activity of a medium-large carnivore. The association between bones of herbivore mammals with conspicuous modifications produced by a large carnivore, and the presence of cub and adult remains of Smilodon, link this felid with at least part of the excavated association. [ABSTRACT FROM AUTHOR]