New records of Neogene Xenarthra (Mammalia) from eastern Puna (Argentina): diversity and biochronology Sofía I. Quiñones, 1 Ángel R. Miño-Boilini, 1 Alfredo E. Zurita, 1 Silvina A. Contreras, 1 Carlos A. Luna, 1 Adriana M. Candela, 2 María Camacho, 3 Marcos D. Ercoli, 4 Natalia Solís, 3 and Diego Brandoni 5 1 Centro de Ecología Aplicada del Litoral (CONICET-UNNE), Ruta 5, km 2,5 CC 128 (3400), Corrientes, Argentina <sofiaiq9@gmail.com> <angelmioboilini@yahoo.com.ar><aezurita74@yahoo.com.ar><sailcontreras11@gmail.com><carlosaluna@hotmail.com> 2 División Paleontología Vertebrados, Museo de La Plata, CONICET, Paseo del Bosque s/n, B1900FWA La Plata, Argentina <acandela@ fcnym.unlp.edu.ar> 3 Instituto de Geología y Minería, Universidad Nacional de Jujuy, Av. Bolívar 1661 +4600 San Salvador de Jujuy, Jujuy, Argentina <mcamachofi@yahoo.com.ar><natsolis@gmail.com> 4 Instituto de Eco-regiones Andinas (INECOA), Universidad Nacional de Jujuy, CONICET, IdGyM, Av. Bolivia 1661, 4600 San Salvador de Jujuy, Jujuy, Argentina <marcosdarioercoli@hotmail.com> 5 Centro de Investigación Científicay de Transferencia Tecnológica a la Producción (CICYTTP-CONICET, Prov E.R., UADER), Materi y España, 3105 Diamante, Entre Ríos, Argentina <dbrandoni@cicyttp.org.ar> Abstract.—Xenarthra is an endemic South American lineage of mammals, probably the sister clade of the other placental mammals. The oldest records of Xenarthra are from the latest Paleocene, although its current diversity is much lower than that recorded in some intervals of the Cenozoic Era. A new Neogene Xenarthra (Pilosa and Cingulata) assemblage from two localities of the Argentine Eastern Puna (Calahoyo and Casira) is described. The newly recorded taxa—Cingulata, Dasypodidae, Eutatini: Stenotatus sp. indet. and Eutatini indet., Euphractini: Macrochorobates scalabrinii (Moreno and Mercerat, 1891), and Tardigrada, Mylodontinae: cf. Simomylodon sp. indet. and Simomylodon cf. S. uccasamamensis Saint-André et al., 2010—and those already published from Calahoyo—Cingulata: Macrochorobates chapadmalensis (Ameghino, 1908), Eosclerocalyptus sp. indet., and Tardigrada, Megatheriidae: Pyramiodontherium bergi (Moreno and Mercerat, 1891)—suggest a middle–late Miocene age for the fossil-bearing levels. In Calahoyo, the presence of Stenotatus sp. indet., in addition to some rodents currently under study in the lower levels, suggest a closer similarity with the palaeofauna of Cerdas (southern Bolivia), probably involving the last part of the Miocene Climatic Optimum. The Xenarthra recorded in the middle and upper levels of Calahoyo and Casira suggest a late Miocene–Pliocene age. A comparative analysis between Calahoyo and Casira highlights the absence of Cingulata in the latter and a high diversity in the former. This situation probably indicates different paleoenvironmental conditions. Finally, we present the first cer- tain record of the genus Simomylodon Saint-André et al., 2010 in Argentina, which includes the oldest record of dermal ossicles for sloths in South America. Introduction South America is characterized by high biogeographic complex- ity due to the heterogeneity of climates and topographies, its great range in latitude (Ortiz-Jaureguizar and Cladera, 2006), and its isolation during a large part of the Cenozoic Era (the so called ‘splendid isolation’ of Simpson, 1980) until the definitive forma- tion of the Isthmus of Panama (Woodburne, 2010;O’Dea et al., 2016). These conditions generated a complex paleobiogeo- graphic and evolutionary scenario that favored the origin and radiation of some clades of endemic mammals, such as Litop- terna, Notoungulata, and Xenarthra (Pascual, 2006; Croft, 2012). Among them, only Xenarthra have living representatives, although their current diversity is a poor representation compared to several intervals of the Cenozoic (Abba et al., 2012; Gaudin and Croft, 2015; Gibb et al., 2015). The monophyly of this group has been repeatedly proved by molecular and morpho- logical analyses (Gaudin, 1995, 2004; Delsuc et al., 2001, 2002; Pujos et al., 2007; Delsuc and Douzery, 2009). Recent molecular evidence indicates that Xenarthra is one of the most basal clades of Placentalia, as the sister group of the remaining mammals (Epitheria) (O’Leary et al., 2013). However, some authors support the interpretation of Xenarthra as the sister group of the Afrotheria (Meredith et al., 2011). Xenarthra includes two large clades, Pilosa (Vermilingua + Tardigrada) and Cingulata (armadillos, pampatheres, peltephi- lids, and glyptodonts) (Delsuc et al., 2002; McDonald and Naples, 2007; Gaudin and Croft, 2015). The earliest record of Xenarthra is the Paleocene (or earliest Eocene?; Gelfo et al., 2009) cingulate dasypodid Riostegotherium yanei Oliveira and Bergqvist, 1998 (Bergqvist et al., 2004). Although the Paleo- gene record of this clade is quite scarce, the beginning of the large radiations and taxonomic diversifications seem to be closely related to certain climatic-environmental events, particu- larly since the Oligocene (Zachos et al., 2001; Ortiz-Jaureguizar and Cladera, 2006; Gibb et al., 2015). However, the paleonto- logical record is much more complete in the Neogene (Gaudin and Croft, 2015). Journal of Paleontology, 93(6), 2019, p. 1258–1275 Copyright © 2019, The Paleontological Society 0022-3360/19/1937-2337 doi: 10.1017/jpa.2019.64 1258 https://doi.org/10.1017/jpa.2019.64 Downloaded from https://www.cambridge.org/core. IP address: 45.162.140.18, on 22 Oct 2019 at 11:57:00, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms.