Chronological implications of the nothrotheriid ‘Xyophorus’ (Mammalia, Xenarthra) from the Collón Curá Formation (Miocene of Patagonia, Argentina)

Abstract

The specimen described herein and assigned to 'Xyophorus' sp. (Mammalia, Xenarthra, Tardigrada) was collected in the locality Cerro Zeballos, northwestern Chubut Province, Argentina. The fossiliferous sediments bearing the specimen are correlated with Collón Curá Formation. The specimen has the features described for other members of 'Xyophorus' (e.g. shape and size of the molariforms, relationship between diastema length, m1 and m2 length) and has a Diastema Length/Tooth Row Length index (DL/TRL index) of ca. 14, between that of 'X. ' villarroeli (12.07) from the Mauri Formation, Bolivia (ca. 10.3 Ma) and that of 'X. ' bondesioi (16.45) from Arroyo Chasicó Formation, Argentina (ca. 10-8.7 Ma). The relationship between DL/TRL index and age of the bearing sediments, would suggest a Tortonian age (late Miocene) for the deposits of Collón Curá Formation at Cerro Zeballos, which results in a 'younger age' compared to the middle Miocene age traditionally accepted for the Collón Curá Formation bearing the Colloncuran fauna sensu stricto. Although no absolute ages for Cerro Zeballos are available yet, the geographic proximity of Cerro Zeballos to Cushamen River (with levels dated at ca. 11.2 Ma) supports the tentative Tortonian age indicated by the presence of 'Xyophorus' sp. 'Xyophorus' corresponds to 'Xyophorus' sp. from the locality of El Petiso (middle Miocene of Chubut Province) (Brandoni 2014). However, there is also one mention of Xyophorus from the Collón Curá Formation (Miocene) at Pilcaniyeu Viejo (Río Negro Province) (Scillato-Yané 1978), but the author did not provide catalogue number and the specimen was never described nor figured. Also from the Collón Curá Formation, Scillato-Yané and Carlini (1998) described Amphibradys guiomari Scillato-Yané and Carlini 1998, based on a fragmentary skull, considered as a Nothrotheriidae-Nothrotheriinae by the authors.

Nothrotheriopssp. (Mammalia, Xenarthra) from the Late Pleistocene of Argentina: implications for the dispersion of ground sloths during the Great American Biotic Interchange

“…11.2 Ma, Chubut Province, Argentina) (Brandoni ; Brandoni et al . ). Lakukullus is recorded from the Serravallian of Quebrada Honda (13–12.7 Ma, Bolivia) (Pujos et al .…”

“…During the Neogene (Fig. 6), Nothrotheriinae is restricted to South America, with records since the Langhian, represented by 'Xyophorus' from the locality of Cerdas (c. 15.1 Ma, Bolivia), but also recorded during the Serravallian of Quebrada Honda (13-12.7 Ma, Bolivia) and the locality known as El Petiso (Chubut Province, Argentina), and the Tortonian of Mauri Formation (c. 10.3 Ma, Achiri, Bolivia), Arroyo Chasic o Formation (10-8.7 Ma, Buenos Aires Province, Argentina) and Cerro Zeballos (c. 11.2 Ma, Chubut Province, Argentina) (Brandoni 2014;Brandoni et al 2017). Lakukullus is recorded from the Serravallian of Quebrada Honda (13-12.7 Ma, Bolivia) (Pujos et al 2014); Pronothrotherium during the late Miocene and early Pliocene of Catamarca and Entre R ıos provinces (Argentina), San Jos e (Uruguay) and Urumaco (Venezuela) (Perea 2007;Latrubesse et al 2010;Brandoni 2013); Aymaratherium from the Zanclean of the locality Pomata-Ayte, Bolivia (Pujos et al 2016), and Mionothropus, sister taxa to the clade Nothrotheriini (Nothrotheriops + Nothrotherium), from the Messinian of R ıo Acre, Peru (De Iuliis et al 2011).…”

Fossil fishes and anurans from the Miocene of Rio Chico and Cerro Zeballos, Chubut Province, Argentina

“…At the North of Chubut River, in front of the confluence with Gualjaina River (Chubut Province), there are extensive outcrops of the Collón Curá Formation (Lage 1982). In this area the sediments were preliminary described by Lage (1982) andBrandoni et al (2019). In this locality, known as Cerro Zeballos (42º 34' 46.5''S, 70º 19' 55''W) (Figure 1), the sequence is homoclinal with subhorizontally disposed strata, and corresponds to volcanoclastic sediments with predominance of tuffs, chonites, and subordinate epiclastic sediments.…”

Early Miocene Sloths (Xenarthra, Folivora) From the Río Santa Cruz Valley (Southern Patagonia, Argentina). Ameghino, 1887 Revisited

“…Among the distinguishing features identified by Brandoni (2014) and Brandoni et al (2017) are that the molariforms, at least mf1 and mf2, are nearly rectangular and mesiodistally compressed and apicobasal sulci are present on the lingual and vestibular surface of at least the mf1 and mf2 of 'Xypohorus' but absent in Xyophorus. However, Brandoni (2014) and Brandoni et al (2017) considered only X. atlanticus, X. simus, and X. crassissimus. The first two…”

“…Xyophorus species erected by Ameghino (1887) were not considered, which is justified given that the original types are lost and were never figured, and the MACN specimens recorded as the types are clearly not so. However, the features present in Ameghino's (1891a) X. sulcatus, for which the type is available (see above), do not agree with some of the distinguishing characters outlined by Brandoni (2014) and Brandoni et al (2017). Ameghino (1891a) Trematherium Ameghino (1887, p. 22) described Trematherium intermixtum as possessing a small and cylindrical cf1, followed by "eliptico-cilíndricas"mf1-mf3, as in Hapalops.…”