Paleogene Glyptodontidae Propalaehoplophorinae (Mammalia, Xenarthra) in extra-Patagonian areas

. Paleogene records of Cingulata Glyptodontidae are scarce. The only well described comes from the Paleogene of Argentine Patagonia. Two subfamilies have been reported for that period: Glyptatelinae and Propalaehoplophorinae. Until this contribution, the latter taxon was geographically restricted to the locality of El Pajarito (Late Oligocene, Deseadan SALMA), Chubut province, Argentina. Here we present and describe the northernmost record of a Paleogene Propalaehoplophorinae. The material is represented by three associated osteoderms of the dorsal carapace from the Fray Bentos Formation (Late Oligocene, Deseadan SALMA) in the locality of Cueva del Tigre, Chajarí, Entre Ríos province, Argentina. Morphologically, these remains are almost identical to those reported from the late Oligocene of the Patagonian region, showing that during the Paleogene the Propalaehoplophorinae had a larger latitudinal distribution than previously known.


Introduction
The Glyptodontidae (Mammalia, Cingulata) comprise an American endemic clade without extant representatives.During a large period of the Cenozoic, these armored herbivores constituted one of the most conspicuous lineages, reaching enormous sizes during some intervals, especially in the Oligocene and Pleistocene (Scillato-Yané, 1977, 1986;Scillato-Yané and Carlini, 1998;Vizcaíno et al., 2011).The oldest records assignable to Glyptodontidae come from the Late Eocene (Mustersian South American Land Mammal Age or SALMA) in the Patagonian region of Argentina and were assigned to the subfamily Glyptatelinae (late Eocene-late Pleistocene).These remains, represented by isolated osteoderms of the dorsal carapace, were described by Ameghino (1902) as Glyptatelus fractus Ameghino (Simpson, 1948;Scillato-Yané, 1977;McKenna et al., 2006).In the Glyptatelinae, the osteoderms of the dorsal carapace are characterized by a central figure displaced posteriorly and surrounded by a row of peripheral figures that are absent on the posterior margin and, in some cases, on the lateral margins as well (Hoffstetter, 1958;Scillato-Yané, 1977).
Most of the few Paleogene records of both subfamilies come from the Argentine Patagonian region.Outside this area, the record is still scarce, and the majority of the materials have not been figured or described.Scillato-Yané (1986, 1988) mentioned the presence of Glyptatelinae nov.sp. and Glyptodontidae incertae sedis for the Late Oligocene (Deseadan SALMA) from Quebrada Fiera, Mendoza province (Argentina).Outside Argentina, Glyptatelinae cf.Glyptatelus sp. was mentioned in the locality of Salla-Luribay (Bolivia) in Late Oligocene sediments (Deseadan SALMA) (Hoffstetter, 1968;Marshall and Sempere, 1991).Finally, Glyptodontidae incertae sedis was recorded from Fray Bentos Formation (Late Oligocene, Deseadan SALMA), outcropping in Uruguay (Ubilla, 2004;Bostelmann et al., 2010Bostelmann et al., , 2011)).In this context, the finding of Paleogene Glyptodontidae becomes important, especially outside Patagonia, because it represents a larger latitudinal distribution for this group during the Oligocene than previously supposed, supporting the presence of other Oligocene cingulates in Fray Bentos Formation (Perea et al., 2014).
Here we describe new remains of Glyptodontidae assignable to Propalaehoplophorinae from the locality of Cueva del Tigre, Entre Ríos province (Argentina) (Fig. 1) from the Fray Bentos Formation (Fig. 2).This is the first extra-Patagonian Paleogene record of these glyptodonts with an adequate description.

Geology
The Fray Bentos Formation was formally defined by Harrington (1956) in Uruguay, where this unit comprises more than 90 m in the Santa Lucía basin, but in outcrops only up to 15-18 m, especially along the Uruguay river, from Colonia up north to the Brazilian border (Ubilla, 2004).These are the "Santalucience" and "Palmirense" units, respectively, described by Kraglievich (1932).This unit is mainly composed of fine and medium sandstones, silts, sometimes calcareous, and conglomerates; the dominant colors are reddish-gray and reddish-brown.According to most authors, they are continental, mainly fluvial and only in part eolian (Goso and Bossi, 1966;Ubilla, 2004).Climatically, they were deposited under warm and dry conditions (Ferrando and Dasa, 1974).This unit has also been recognized in Argentina, more precisely in Corrientes and Entre Ríos provinces (Herbst, 1980;Herbst and Santa Cruz, 1999), based on the very close similarity of its lithology and stratigraphic position: directly over the Serra Geral basalts and the Plio-Pleistocene sands and conglomerates of the Salto (or Ituzaingó) Formation (Fig. 2).In Argentina, the unit is composed of "very fine sandstones to silts, with clayish to calcareous-clayish cements" (Herbst, 1980: 309).In the provinces of Corrientes and Entre Ríos, Herbst (1980) recognized two sections: a lower one known as "calcareous sediments of Curuzú Cuatiá" and an upper one composed of reddish lime-sandstones.
The materials herein described come from the latter, corresponding to this upper section (Fig. 2).

Materials and methods
The materials studied are housed in the paleontological collection of the Universidad Nacional del Nordeste, Facultad de Ciencias Exactas y Naturales y Agrimensura, Corrientes, Argentina (CTES-PZ).The materials for comparison correspond to specimens of Glyptatelinae, Propalaehoplophorinae, "Hoplophorinae" Palaehoplophorini, Hoplophorini, and Neosclerocalyptini; Glyptodontinae and Glyptodontidae incertae sedis hosted in the following institutions: American Museum of Natural History, New York, USA (AMNH); División Paleontología

Description and comparisons:
The three osteoderms show a finely dotted exposed surface and an evident "rosette" ornamentation pattern (Figs. 3 and 4).This pattern consists of a polygonal central figure delimited by a central groove, from which radial grooves that define peripheral figures (anterior, lateral and posterior) emerge and surround the central one.An evident foramen is present in most of the intersections between the radial grooves and the groove that defines the central figure (Ameghino, 1889).The grooves delimiting the peripheral figures are shallow and parabolic in sagittal section ("V"shaped; see Carlini et al., 2008).peripheral figures (Figs. 3 and 4).The presence of these small accesory figures allows assigning these osteoderms to the lateral region of the dorsal carapace, because it is the region in the carapace of the Propalaehoplophorinae where they are usually developed.(Scott, 1903(Scott, -1904;;González, 2010).One of the osteoderms (Fig. 3C) probably corresponds to a more lateral region of the carapace, since it has a great development of the anterior peripheral figures, while the posterior ones are much less visible, as observed in the Neogene species of Propalaehoplophorinae (e.g., Propalaehoplophorus minus).
The contact area and articulation between adjacent osteoderms is relatively f lat, although rather rough.The ventral surface of each osteoderm is slightly concave in its central area, where 3-6 larger foramina can be seen.The osteoderms measure: (A) 35.24 mm (antero-posterior diameter) x 26.56 mm (dorso-ventral diameter) x 9.71 mm (transverse diameter); (B) 32.65 mm x 32.42 mm x 9.85 mm; (C) 37.44 mm x 31.42 mm x 9.27 mm.(Fig. 2).
The morphology of the exposed surface of the osteoderms described here is clearly different from that of Paleogene Glyptatelinae (Glyptatelus fractus, Glyptatelus tatusinus and Clypeotherium magnum), in which the central figure reaches the posterior edge, the peripheral figures are limited to the anterior and lateral edges (the lateral ones generally reduced or absent), there are no accessories latero-anterior peripheral figures, and the figures are convex and rounded (except in Clypeotherium where they are flat), and the grooves that delimit the figures are deep (Ameghino, 1897;Hoffstetter, 1958;Scillato-Yané, 1977.In addition to this, we observed only two or three large anterior figures in most of the osteoderms, whereas in Glyptodontidae Propalaehoplophorinae there are generally four.In this scenario, it is remarkable that most of the Glyptatelinae characters are absent in Glyptatelus malaspinensis, suggesting that the type material (osteoderms) corresponds in fact to a Propalaehoplophorinae, but further studies are necessary.Compared to Parapropalaehoplophorus (Glyptodontidae incertae sedis) the osteoderms of Propalaehoplophorinae indet.From the Fray Bentos Formation are different because they have conspicuous foramina in the intersection of the grooves that delimit the figures and the presence of the typical "rosette" pattern, both characters absent in Parapropalaehoplophorus.

Discussion
At the level of the osteoderms of the dorsal carapace, the "rosette" ornamentation pattern (i.e., a central figure surrounded by a complete row of peripheral figures) appears for the first time in Propalaehoplophorinae glyptodonts (Ameghino, 1889;Scott, 1903Scott, -1904) ) during the Late Oligocene (see Scillato-Yané, 1977).This pattern probably originated from a previous one (with a smaller number of lateral peripheral figures and absence of posterior peripheral figures) present in the Glyptatelinae and in a Glyptodontidae incertae sedis (Parapropalaehoplophorus) of the Early and Middle Miocene of northern Chile and Perú (Hoffstetter, 1958;Carlini et al., 1997;Croft et al., 2007;Tejada et al., 2011).Although the Glyptatelinae pattern is apparently observed in Parapropalaehoplophorus, in some osteoderms from the lateral region of the carapace of the Propalaehoplophorinae, and in fixed osteoderms of Cingulata Dasypodidae, there are differences between all of them, such as the position of the central (=principal) figure in dorsal osteoderms (along the posterior edge, near posterior edge, or roughly central, among others; see Croft et al., 2007).
The "rosette" pattern is present practically unchanged in all genera of Propalaehoplophorinae (see Scott, 1903Scott, -1904;;Scillato-Yané, 1977, 1986;González, 2010).In the genus Cochlops Ameghino, 1889, at the level of the pelvic region, osteoderms present a clear "cone-like" elevation, in both central and peripheral figures, showing some analogy with that observed in the peripheral osteoderms of Glyptodontinae (Ameghino, 1889;Zurita et al., 2013).In the same region, Propalaehoplophorus shows some convexity in the central figures of the osteoderms although such elevation is not as marked as in Cochlops.However, in any case, the "rosette" pattern is not modified.The comparison between the Oligocene osteoderms described and figured by Scillato-Yané (1977) and those studied here shows that there are no significant differences in morphology or size.In fact, the osteoderms A and B figured here are almost identical to those figured by Scillato-Yané (1977, plate II) as 1 and 3, whereas the osteoderm C is very similar to that figured and numbered as 7.
The Neosclerocalyptini (e.g., Neosclerocalyptus) also show a "rosette" ornamentation pattern, which, in some sectors of the carapace, presents a remarkable similarity with the Propalaehoplophorinae (see Zurita, 2007).However, and in contrast to that observed in this subfamily, the lateral osteoderms show an equivalent development of the peripheral figures in the anterior and posterior edges.In fact, in the Propalaehoplophorinae, the more antero-lateral region of the carapace presents a very different morphology from that of Eosclerocalyptus C. Ameghino, 1919 andNeosclerocalyptus Paula Couto, 1957.In Neosclerocalyptini, the osteoderms of this region have a pentagonal or hexagonal outline while in the Propalaehoplophorinae the osteoderms have a clear rectangular morphology.
Finally, another group is represented by the subfamily Glyptodontinae (middle-late Mioceneearly Holocene) (e.g., Boreostemma Carlini et al., 2008 andGlyptodon Owen, 1839).However, in this clade, there are trends that allow differentiating them from the Propalaehoplophorinae.This group shows a progressive increase in the roughness of the exposed surface, an increase in the denticulation of the area of contact between adjacent osteoderms, an increase in the thickness of the osteoderms, and grooves that delimit the figures in "U" shape, together with the absence of additional small peripheral figures and fewer small peripheral figures (Carlini et al., 2008;Zurita et al., 2013).

Conclusions
The comparative study shows that the morphology of the exposed surface of the osteoderms studied in this contribution is almost identical to the other Paleogene record assigned to Propalaehoplophorinae coming from the Patagonian region of Argentina.From a paleobiogeographical perspective, as mentioned above, the Paleogene records of Propalaehoplophorinae are scarce.Until this contribution, these were limited with certainty to one record from the Argentine Patagonia (Scillato-Yané, 1977).Although Bostelmann et al. (2010) mentioned the probable presence of Propalaehoplophorinae indet.In Nueva Palmira (Uruguay), he reinterpreted the specimens as belonging to Glyptodontidae incertae sedis (Bostelmann et al., 2011).However, only the Patagonian Propalaehoplophorinae records have been figured (Scillato-Yané, 1977, plate II).
In summary, this is the northernmost record of a Paleogene Propalaehoplophorinae, thus significantly expanding its latitudinal distribution, which now ranges from 43°51´ S to 30°46´ S.This indicates that during the Paleogene, the Propalaehoplophorinae had a larger latitudinal distribution than previously supposed.
FIG. 2. Stratigraphic profile showing the location of the osteoderms.