Submitted: December 19th, 2019 – Accepted: April 20th, 2020 – Published online: April 27th, 2020
To link and cite this article:
doi: 10.5710/AMGH.20.04.2020.3329
1 NEW DATA ON THE DIVERSITY OF NOTOUNGULATA (MAMMALIA) FROM
2 THE FRAY BENTOS FORMATION (LATE OLIGOCENE) IN CORRIENTES
3 PROVINCE, ARGENTINA
4 NUEVOS DATOS SOBRE LA DIVERSIDAD DE NOTOUNGULATA (MAMMALIA)
5 DE LA FORMACIÓN FRAY BENTOS (OLIGOCENO TARDÍO) EN LA PROVINCIA
6 DE CORRIENTES, ARGENTINA
7 ESPERANZA CERDEÑO1, GABRIELA I. SCHMIDT2, ÁNGEL R. MIÑO-BOILINI3
8 AND ALFREDO E. ZURITA3
9 1Paleobiología y Paleoecología, Instituto Argentino de Nivología, Glaciología y Ciencias
10 Ambientales (IANIGLA), Centro Científico Tecnológico-CONICET-Mendoza. Avenida
11 Ruiz leal s/n, M5500 Mendoza, Argentina. [email protected]
12 2Laboratorio de Paleontología de Vertebrados, Centro de Investigación Científica y de
13 Transferencia Tecnológica a la Producción (CICYTTP-CONICET)-Prov. ER-UADER,
14 España 149, E3105BWA, Diamante, Entre Ríos, Argentina. [email protected]
15 3Centro de Ecología Aplicada del Litoral (CECOAL-CONICET) y Universidad Nacional
16 del Nordeste. Ruta 5, Km 2,5, cc 128, 3400, Argentina. [email protected],
18 39 pages (text+references); 3 figures; 6 tables.
19 Proposed header: CERDEÑO ET AL.: LATE OLIGOCENE NOTOUNGULATA FROM
20 CORRIENTES
21 Short description: Notoungulate remains from the Deseadan Fray Bentos Formation in
22 Corrientes Province are revised and taxonomically updated.
23 Corresponding author: Esperanza Cerdeño, [email protected]
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24
25 Abstract. We revise the mammal fossils from the Fray Bentos Formation previously
26 assigned to Notoungulata, as well as some new remains recovered from levels cropping out
27 in Corrientes Province (Argentina). In some cases, previous determinations have been
28 completed to the species level, but others have been substantially modified, identifying
29 different families. At present, identified taxa are: “Prohegetotherium” schiaffinoi
30 (Hegetotheriidae), an undetermined interatheriid that is hypothesized as representing the
31 upper teeth of Eopachyrucos ranchoverdensis, and Argyrohyrax proavus (Interatheriidae),
32 cf. Archaeohyrax suniensis (Archaeohyracidae), cf. Mendozahippus fierensis
33 (“Notohippidae”), a Leontiniidae indet., and some undetermined Notoungulata. The
34 presence of Leontiniidae is based on the specimen CTES-PZ 7871, but those previously
35 assigned to this family are herein discarded as such and reinterpreted (notohippid and
36 undetermined taxon). The Mesotheriidae are discarded among the revised materials, but
37 they are present in the Fray Bentos Formation in Corrientes Province with Trachytherus
38 spegazzinianus (= Ameghinotherium curuzucuatiense). The revised sample presents
39 affinities with the fauna from the type locality of the Fray Bentos Formation, in Uruguay,
40 and the Deseadan assemblages from Quebrada Fiera (Mendoza Province, Argentina),
41 Patagonia (Argentina), and Salla (Bolivia). These similarities are important from a
42 paleobiogeographic point of view, especially by the recognition of cf. M. fierensis, a
43 species only known from Mendoza up to now. Only the finding of new material from Fray
44 Bentos Formation in Corrientes Province will allow us to corroborate these tentative
45 determinations and a possible eastward extension of up-to-now exclusive taxa from
46 Quebrada Fiera.
47 Key words. Native ungulates. Cenozoic. Deseadan. Corrientes. Argentina. South America.
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48 Resumen. NUEVOS DATOS SOBRE LA DIVERSIDAD DE NOTOUNGULATA
49 (MAMMALIA) DE LA FORMACIÓN FRAY BENTOS (OLIGOCENO TARDÍO) EN
50 LA PROVINCIA DE CORRIENTES, ARGENTINA. Se revisan los restos atribuidos
51 previamente a distintos taxones de notoungulados procedentes de la Formación Fray Bentos
52 que aflora en la provincia de Corrientes (Argentina). En unos casos, se ha completado la
53 determinación taxonómica hasta el nivel de especie, pero en otros se ha modificado
54 radicalmente, adjudicando los restos a familias diferentes de las consideradas previamente.
55 Los notoungulados presentes son: “Prohegetotherium” schiaffinoi (Hegetotheriidae), un
56 interatérido indeterminado para el que se plantea la hipótesis de que representa los
57 premolares superiores de Eopachyrucos ranchoverdensis, y Argyrohyrax proavus
58 (Interatheriidae), cf. Archaeohyrax suniensis (Archaeohyracidae), cf. Mendozahippus
59 fierensis (“Notohippidae”), un Leontiniidae indet. y varios ejemplares indeterminados. La
60 presencia de Leontiniidae se basa en el espécimen CTES-PZ 7871, pero se descartan y
61 reinterpretan (notohípido y taxón indeterminado) los atribuidos previamente a esta familia.
62 Los Mesotheriidae no se reconocen entre el material revisado, pero están presentes en la
63 Formación Fray Bentos en la provincia de Corrientes con Trachytherus spegazzinianus (=
64 Ameghinotherium curuzucuatiense). La muestra revisada presenta semejanzas con la fauna
65 de la localidad tipo de la Formación Fray Bentos, en Uruguay, y con las asociaciones
66 deseadenses de Quebrada Fiera (provincia de Mendoza, Argentina), Patagonia (Argentina)
67 y Salla (Bolivia). Estas similitudes tienen gran importancia paleobiogeográfica,
68 especialmente por el reconocimiento de cf. M. fierensis, conocido hasta ahora únicamente
69 en Mendoza. Solo la obtención de nuevos materiales de la Formación Fray Bentos en
70 Corrientes permitirá corroborar las determinaciones tentativas y la posible extensión hacia
71 el este de taxones hasta ahora exclusivos de Quebrada Fiera.
3
72 Palabras clave. Ungulados nativos. Cenozoico. Deseadense. Corrientes. Argentina.
73 América del Sur.
4
74
75 THE FRAY BENTOS FORMATION was defined by Harrington (1956) in Uruguay, where it
76 crops out along the Uruguay River, from Colonia to the Brazilian boundary, with a
77 thickness of 15–18 m (Ubilla, 2004). This unit is mainly composed of continental fine to
78 medium sandstones, silts, sometimes calcretes and conglomerates, mainly reddish grey to
79 reddish brown; they are principally of fluvial origin, and only partially eolian (Ubilla,
80 2004). From a climatic point of view, these sediments were deposited under warm and dry
81 conditions (Ferrando & Dasa, 1974). In the current territory of Argentina, the Fray Bentos
82 Formation has been also recognized in the provinces of Corrientes and Entre Ríos (Herbst
83 and Santa Cruz, 1999), where this unit is composed of very fine sandstones to silts, with
84 clay to calcareous-clay cements (Herbst, 1980: 309). In turn, Álvarez (1978) and Herbst
85 (1980) differentiated two sections: the lower "sedimentos calcáreos de Curuzú Cuatiá"
86 (calcareous sediments of Curuzú Cuatiá) and the upper section composed of reddish
87 limestone-sands. Nevertheless, most fossils lack a precise stratigraphic provenance and
88 only a general datum is provided in old labels and publications (e.g., Río Corrientes; see
89 below for each taxon). Some were collected in sediment removals during public works, and
90 even the most recently recovered material lack precise data, as they have been occasional
91 findings in a quarry.
92 Fossil mammals from the Fray Bentos Formation in Corrientes and Entre Ríos
93 provinces (Fig. 1) are represented by xenarthrans, native ungulates, and rodents, previously
94 studied and mentioned by Podestá (1899), Álvarez (1978), Bond et al. (1998), Reguero
95 (1999), Carlini et al. (2007), and Zurita et al. (2016). The age of this formation has been
96 restricted to the late Oligocene, Deseadan South American Land Mammal Age—
97 SALMA—(Ubilla, 2004; Perea et al., 2014).
5
98 The Deseadan SALMA represents an important temporal interval in the South
99 American mammal evolution, with the appearance of some groups of xenarthrans,
100 notoungulates, litopterns, and marsupials (Dozo et al., 2014; Woodburne et al., 2014; and
101 references therein) and a great diversity of caviomorph rodents (Vucetich et al., 2015); it is
102 also the epoch with the last appearance of different groups of mammals such as pyrotheres,
103 Trachytheriinae mesotheriids, or archaeohyracids (Woodburne et al., 2014; Croft, 2016).
104 Deseadan fossil-bearing sediments in Argentina are mainly known in Patagonia (Chubut
105 and Santa Cruz provinces), but they are also represented in Entre Ríos, Corrientes, and
106 Mendoza provinces (e.g., Bond et al., 1998; Cerdeño & Vera, 2017; and references
107 therein). Outside Argentina, Deseadan faunas are known from Bolivia, Brazil, Uruguay,
108 and Peru (e.g., see Shockey et al., 2016).
109 The purpose of this contribution is to revise the specimens of Notoungulata
110 exhumed from the Fray Bentos Formation in Corrientes Province, updating their taxonomic
111 status after comparisons with presently known Deseadan faunas. The fossil-bearing
112 localities are located in the SE of the province, and are reduced in extension, including Río
113 Corrientes, Arroyo María Grande, Arroyo Ávalos, and south of Curuzú Cuatiá, all of them
114 in the Curuzú Cuatiá Department (Álvarez, 1978).
115 Institutional abbreviations. MACN A, Museo Argentino de Ciencias Naturales “B.
116 Rivadavia”, Ameghino Collection, Buenos Aires, Argentina; MAMC, Museo de
117 Arqueología de Canelones, Canelones, Uruguay; MCNAM-PV, Museo de Ciencias
118 Naturales y Antropológicas “J. C. Moyano”, colección Paleontología de Vertebrados,
119 Mendoza, Argentina; MLP, Museo de La Plata, colección Paleontología de Vertebrados,
120 La Plata, Argentina; MNHN-BOL-V, Museo Nacional de Historia Natural-Vertebrados, La
6
121 Paz, Bolivia; MNHN-SAL, Muséum national d’Histoire naturelle, Paris, France; UF,
122 University of Florida, Gainsville, USA.
123 Anatomical and metrical abbreviations. c, lower canine; L, length; M/m, upper/lower
124 molar; P/p, upper/lower premolar; W, width.
125 MATERIAL AND METHODS
126 The studied material belongs to the Colección Paleontológica de la Universidad
127 Nacional del Nordeste “Dr. Rafael Herbst”, Corrientes Province (Argentina), and the
128 specimens are recognized with the acronym CTES-PZ. Most of them were previously
129 ascribed to different notoungulate taxa by Álvarez (1978) and Bond et al. (1998). Some
130 were also included in posterior papers focused on different families, as detailed along the
131 text. Just a few remains have been recently collected during 2012.
132 New morphological and metrical data, as well as photographs, have been taken for
133 each specimen. Photos were taken with a camera Sony a7S, lens Nikon micro 55mm f2.8
134 Ai-s and through a stereoscopic microscope NIKON SMZ745T. Former publications
135 whether did not illustrate (Álvarez, 1978; Reguero & Castro, 2004; Reguero & Cerdeño,
136 2005) or only partially schematized (Bond et al., 1998) these materials.
137 The hegetotheriid specimens CTES-PZ 3748–3749 were wrongly indicated as
138 coming from the Entre Ríos Province (Argentina) by Bond et al. (1998) and Reguero &
139 Cerdeño (2005). Álvarez (1978) had referred them as coming from the Río Corrientes
140 locality and so they appear in the old inventory book (Río Corrientes, Perugorría).
141 The taxonomic determinations are based on morphological and metrical
142 comparisons with other Deseadan specimens stored in several Argentinean institutions (see
143 Abbreviations above) and on bibliographic data.
144 SYSTEMATIC PALEONTOLOGY
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145 Order NOTOUNGULATA Roth, 1903
146 Family HEGETOTHERIIDAE Ameghino, 1894a
147 Genus Prohegetotherium Ameghino, 1897
148 Type species. Prohegetotherium sculptum Ameghino, 1897
149 “Prohegetotherium” schiaffinoi (Kraglievich, 1932)
150 Figure 2.1–2.16
151 Material and origin. Río Corrientes, Perugorría, Curuzú Cuatiá Department, upper
152 “section”: CTES-PZ 3744, right mandibular fragment with m3; CTES-PZ 3748–CTES-PZ
153 3749, right mandibular fragments with p3–m2 and m3, respectively, from the same
154 individual; CTES-PZ 3751, left mandibular fragment with m1–3 (incomplete m3); CTES-
155 PZ 7872, left mandibular fragment with p3–m3. Arroyo Ávalos, Perugorría, Curuzú Cuatiá
156 Department, upper “section”: CTES-PZ 3755, left mandibular fragment with p3–4; CTES-
157 PZ 3756, right mandibular fragment with p4–m1; CTES-PZ 3766, right upper molar (M1);
158 CTES-PZ 3767, right upper premolar (P4).
159 Description. CTES-PZ 3755 and CTES-PZ 7872 (Figs. 2.7–2.8, 2.15–2.16) show the p3
160 with trigonid well differentiated from talonid; the former is anterolingually rounded and
161 posterolabially elongated; the lingual groove that separates it from talonid is more
162 anteriorly placed than the labial groove; the talonid is triangular and larger than the
163 trigonid. The p4 (fractured) in CTES-PZ 3755 shows a rounded trigonid, anterolabially
164 oriented, and the talonid with a smooth posterolingual fold projecting from the lingual wall;
165 the p4 in CTES-PZ 7872 is very similar, with more detached posterolingual fold. The same
166 shape and orientation of the trigonid are present in the molars of this specimen, with small
167 variations in the more or less square outline. The talonid is triangular in m1–2, shorter and
168 more pointing in m1. Both molars present the lingual wall with the posterior fold more
8
169 conspicuous than p4. The m3 in CTES-PZ 3744 and CTES-PZ 3749 (Figs. 2.1, 2.3) shows
170 a well-marked posterolingual fold, although it does not project lingually but is an inflexion
171 of the wall; the labial face of the talonid is regularly convex in these specimens whereas it
172 presents a smooth posterolabial concavity in CTES-PZ 7872, in which the posterolingual
173 fold is more projected. In CTES-PZ 3748 (Fig. 2.3), premolars and molars present a
174 comparable outline to that described; they are horizontally broken and the bottom of a small
175 fossettid is observed, which indicates an individual with less advanced ontogenetic stage
176 than the other specimens (e.g., see Cerdeño & Reguero, 2015 about the presence of
177 remnants of a central fossette/fossettid in hegetotheriids).
178 The m1 in CTES-PZ 3751 (Fig. 2.5–2.6) differs from the m1 in CTES-PZ 3744 and
179 CTES-PZ 7872 in having a lingual wide concavity opposite to the ectoflexid; so, more
180 anteriorly placed than in the latter specimens in which a smoother lingual concavity is on
181 the talonid.
182 The specimen CTES-PZ 3756 (Fig. 2.9–2.10) shows the particularity in both teeth
183 of having a neat detachment of their labial vertex, and at least the m1 also presents a labial
184 concavity (see comments below about this specimen).
185 The two upper teeth are similar to each other, with smoothly convex ectoloph,
186 without conspicuous folds, and without posterolingual groove. The difference among them
187 lays on the trapezoidal occlusal outline, anterolingually convex in CTES-PZ 3767 (Fig.
188 2.13–14), interpreted as P4, and more squared in CTES-PZ 3766 (Fig. 2.11–2.12), in which
189 the anterior wall is more angled to the lingual one, interpreted as M1.
190 Comments and comparisons. Álvarez (1978) assigned to Prohegetotherium sp. the
191 specimens CTES-PZ 3744 (wrongly interpreted as m2), CTES-PZ 3748, and CTES-PZ
192 3749; to Propachyrucos sp., CTES-PZ 3751, CTES-PZ 3755, CTES-PZ 3756 (as p3–4),
9
193 CTES-PZ 3766 (as probable M2), and CTES-PZ 3767 (as probable P4); and to
194 Hegetotheriidae, CTES-PZ 3778, but this remain corresponds to an Archaeohyracidae (see
195 below). Bond et al. (1998) recognized most of them (except CTES-PZ 3778 and CTES-PZ
196 3756) as Prohegetotherium sp. Later, Reguero and Cerdeño (2005) identified as
197 Prohegetotherium schiaffinoi: CTES-PZ 3755, CTES-PZ 3766, CTES-PZ 3767
198 (recognized as a P3), CTES-PZ 3744, and CTES-PZ 3748–3749 (as p2–m1 and m3). These
199 authors did not include CTES-PZ 3751 or CTES-PZ 3756.
200 The described morphology of cheek teeth coincides with that of the specimens
201 assigned to “Prohegetotherium” schiaffinoi, as Reguero & Cerdeño (2005) stated from
202 comparison with the Bolivian material from Salla. Later, Cerdeño and Reguero (2015)
203 added to this species several specimens from the Deseadan locality of Quebrada Fiera
204 (Mendoza Province, Argentina). Comparing directly with the latter sample, for instance
205 MCNAM-PV 4061 shows the described features: p3 with elongated trigonid, posterolingual
206 projection of m1–2, and posterolingual inflexion of m3 (these features can be present in
207 some Miocene hegetotheriids [Cerdeño & Reguero, 2015; Seoane & Cerdeño, 2019; Vera,
208 2019], although having a different elongation of p3 or variable inflexion/groove in m3).
209 Concerning upper dentition, the two described teeth are more sub-squared than the
210 homologous teeth in the holotype from the Fray Bentos Formation in Uruguay, which can
211 be partly due to a different wear degree (see intraspecific variation interpreted by Cerdeño
212 & Reguero, 2015). Comparing with the larger sample of “P.” schiaffinoi from Quebrada
213 Fiera, CTES-PZ 3767 is similar to the worn P4, closer to MCNAM-PV 4188 (more worn)
214 than to MCNAM-PV 3959 (Cerdeño & Reguero, 2015: fig. 4C and 4B, respectively). The
215 outline of CTES-PZ 3766 coincides with that of M1 of this species. The size of revised
10
216 lower and upper remains (Tab. 1) also matches the variation range of “P.” schiaffinoi
217 (Cerdeño & Reguero, 2015: tab. 2).
218 CTES-PZ 3756 deserves a particular comment, as the differentiation of the labial
219 vertex of talonid and the lingual concavity are not common in hegetotheriids; in fact, Bond
220 et al. (1998) considered this specimen as belonging to an archaeohyracid. However, it does
221 not show the archaeohyracid morphology (see below other material of this group); instead,
222 the labial feature of the talonid is similar to the condition observed in MLP 96-XI-20-9
223 (m1–2) of “P.” schiaffinoi from Quebrada Fiera (Cerdeño & Reguero, 2015, not figured);
224 less marked but insinuated, this is also observable in MCNAM-PV 4637 (Cerdeño &
225 Reguero, 2015: fig. 5F). In turn, the lingual concavity is also observed in CTES-PZ 3751
226 (see description) or the m1 of the mandible UF 91661 of “P.” schiaffinoi from Salla
227 (Bolivia; Cerdeño & Reguero, 2015: fig. 5G). It is present as well in other hegetotheriid
228 taxa, such as the late Oligocene–early Miocene Hegetotheriopsis sulcatus Kramarz & Paz,
229 2013 (see fig. 3.2, and also Kramarz & Bond, 2017) or Hegetotherium mirabile Ameghino,
230 1887a (see Seoane & Cerdeño, 2019: fig. 1E, 1K, 2E). Kramarz & Bond (2017) recognized
231 as H. sulcatus the Deseadan material from Quebrada Fiera previously recognized as
232 Prohegetotherium sp. (Cerdeño & Reguero, 2015: fig. 3), remains that are greater in size
233 and differ in morphology from those herein studied: the upper teeth show a more undulate
234 ectoloph and the lower tooth, an m3, presents a lingually convex talonid, with a labial
235 groove.
236 According to Kramarz & Bond (2017), materials classically attributed to the genus
237 Prohegetotherium need a detailed revision, as these authors limit the type species, P.
238 sculptum, to the two type specimens (MACN A 52-443 and MACN A 52-444, maxillary
239 and cranial fragments, respectively, with cheek teeth). This reinterpretation led Kramarz &
11
240 Bond (2017) to questioning the previously established synonymies and many of the
241 features used to characterize P. sculptum (e.g., lower dentition features) and, thus,
242 Prohegetotherium. These authors stated that P. sculptum differs from other hegetotheriines
243 in the upper premolar morphology, the position of the alveolus of upper canine, and the
244 extension of the maxillary crest to the infraorbital foramen (Kramarz & Bond, 2017: 1028).
245 In this context, they referred the species P. schiaffinoi as “Prohegetotherium” schiaffinoi.
246 In addition, in their phylogenetic analysis, this taxon appeared in a polytomy and separated
247 from both P. sculptum and “P.” malalhuense Cerdeño & Reguero, 2015. This phylogenetic
248 position contrasted with the clade obtained by Seoane et al. (2017), in which P. sculptum
249 appears as the sister group of [P. schiaffinoi + P. malalhuense]); however, in a more recent
250 analysis carried out by Seoane & Cerdeño (2019), Prohegetotherium resulted again
251 paraphyletic. The latter authors indicated the need of a deep revision of all materials
252 assigned to Prohegetotherium and particularly of those excluded from P. sculptum by
253 Kramarz & Bond (2017). In the meanwhile, the specimens herein studied are identified as
254 “Prohegetotherium” schiaffinoi.
255 The species “P.” schiaffinoi was originally defined by Kraglievich (1932) as
256 Propachyrucos? schiaffinoi based on a maxillary fragment from the Fray Bentos Formation
257 at San Gregorio, Uruguay. Posteriorly, Reguero (1999) and Reguero & Cerdeño (2005)
258 considered it as part of the genus Prohegetotherium. Its presence in the Fray Bentos
259 Formation in Corrientes Province results, then, coherent with its initial record in levels of
260 the same formation in Uruguay. Despite this, Bond et al. (1998) only reached the generic
261 level, Prohegetotherium sp., from the study of CTES-PZ 3744, CTES-PZ 3748-3749, and
262 CTES-PZ 3755, herein re-described. These specimens (except CTES-PZ 3751, not
263 included) were attributed to P. schiaffinoi by Reguero & Cerdeño (2005). However, the
12
264 same authors excluded later CTES-PZ 3748-3749 from this species (Cerdeño & Reguero,
265 2015: 5), due to the convexity of the lingual walls (wrongly signaled as labial) and to the
266 lack of posterolingual inflexion in m3, according to the schematic figure published by Bond
267 et al. (1998). The present revision shows that this scheme was not confident, as it did not
268 indicate either the smooth posterolingual fold in p4–m2 (CTES-PZ 3748) or the
269 posterolingual inflexion that is present in m3 CTES-PZ 3749; in addition, the scheme
270 indicated a labial fold in the talonid that is actually an enamel break and not a fold. With
271 respect to the convexity of the lingual wall, it seems to be slightly more convex than in the
272 specimens from Quebrada Fiera, but there is some variation among this sample (e.g.,
273 Cerdeño & Reguero, 2015: fig. 5A-F: 5A and 5C with more convex lingual walls). In
274 consequence, we reconsider CTES-PZ 3748–CTES-PZ 3749 as “P.” schiaffinoi.
275 Family INTERATHERIIDAE Ameghino, 1887b
276 Interatheriidae indet.
277 Figure 2.17
278 Material and origin. Arroyo María Grande, Perugorría, Curuzú Cuatiá Department: CTES-
279 PZ 3775, maxillary fragment with right P3–4.
280 Description. The upper premolars in CTES-PZ 3775 show strong parastyle and paracone
281 fold, the former well extended anteriorly and more lingually placed than the latter (Fig.
282 2.17); they are separated by a deep groove; both folds are almost parallel and the paracone
283 fold does not direct labially from the rest of the ectoloph; both premolars have an irregular
284 central fossette, badly preserved in P3. P4 is broadly overlapping P3.
285 Comments and comparisons. Álvarez (1978) did not recognize any specimen as
286 Interatheriidae, whereas Bond et al. (1998) assigned CTES-PZ 3768 (see below) to
287 Interatheriinae indet. and CTES-PZ 3775 to Plagiarthrus sp. (= Argyrohyrax Ameghino,
13
288 1897, see Vera et al., 2017). More recently, Vera et al. (2017) included the Fray Bentos
289 Formation (in Corrientes Province) in the distribution of the species Argyrohyrax proavus
290 Ameghino, 1897, but they did not detail the considered material, just referring to Bond et
291 al. (1998). On the other hand, Reguero et al. (2003a) described the interatheriine species
292 Eopachyrucos ranchoverdensis from the Fray Bentos Formation in Uruguay.
293 The long parastyle and the great depth of the labial sulcus in upper premolars are
294 present in a few interatheriine species. It is the case of the Deseadan Brucemacfaddenia
295 boliviensis Hitz, Billet, & Derryberry, 2008, from Salla (Hitz et al., 2008: fig. 2), but this
296 species clearly differs in having parastyle and paracone fold labially directed from the rest
297 of the ectoloph (especially evident in the holotype), and the latter is more undulated. In this
298 aspect, CTES-PZ 3775 resembles more the Patagonian Cochilius volvens Ameghino, 1902
299 (e.g., Simpson, 1932: fig. 2), in which, however, the folds still direct a little labially and the
300 ectoloph is slightly concave, not so straight as in CTES-PZ 3775, and the groove penetrates
301 the occlusal face more lingually directed. Compared with the Deseadan interatheriines
302 described by Vera et al. (2017), CTES-PZ 3775 is closer to Argyrohyrax proavus (e.g.,
303 MCNAM-PV 4233 from Quebrada Fiera) than to Progaleopithecus fissurelatus Ameghino,
304 1904; the former still differs in having more molarized premolars, with shallower labial
305 groove and more undulated ectoloph; the latter has deeper groove (even in molars), but the
306 folds direct labially and there is a neat labial concavity posterior to the paracone fold.
307 CTES-PZ 3775 cannot be properly compared with Eopachyrucos ranchoverdensis,
308 because this species is only known by the lower dentition (Reguero et al., 2003a). Even the
309 older, Patagonian, type species of this genus, E. pliciferus, only counts with one known
310 upper molar, the holotype (Hitz et al., 2000: 22; fig. 13C). However, as no other Deseadan
311 species coincides with the morphology described for CTES-PZ 3775, it is plausible to
14
312 hypothesize that these premolars could represent the upper dentition of E. ranchoverdensis.
313 Their size (Tab. 2) is slightly smaller than that of A. proavus (Vera et al., 2017, tab. 1), and
314 greater than the holotype of E. pliciferus (after measurements in Hitz et al., 2000: 22). The
315 lower teeth of E. ranchoverdensis are also greater than those of E. pliciferus (Reguero et
316 al., 2003a); compared with A. proavus (Vera et al., 2017: table 3), premolars are greater
317 whereas molars fall within the variation range of this species; the three specimens of E.
318 ranchoverdensis show some variation in size, especially in molar lengths (Reguero et al.,
319 2003a: table 4) as it happens in A. proavus. It is evident that a confident determination of
320 CTES-PZ 3775 is not possible, and only new material will support or not the hypothesis
321 that it could belong to E. ranchoverdensis, as well as it will reveal to what extent the upper-
322 tooth size can vary.
323 Genus Argyrohyrax Ameghino, 1897
324 Type species. Argyrohyrax proavus Ameghino, 1897
325 Argyrohyrax proavus Ameghino, 1897
326 Figure 2.18–2.20
327 Material and origin. Río Corrientes, Perugorría, Curuzú Cuatiá Department: CTES-PZ
328 3750, left mandibular fragment with remains of three teeth (m1–3?). Arroyo María Grande,
329 Perugorría, Curuzú Cuatiá Department, lower “section”: CTES-PZ 3768, right mandibular
330 fragment with c–p1.
331 Description. CTES-PZ 3768 (Fig. 2.19–20) is a badly preserved fragment with two teeth
332 interpreted as right c–p1, without wear, and root remains behind them. These teeth are
333 subtriangular in outline, the canine shorter than the p1 and overlapping it; both present a
334 principal cusp. In the canine, this cusp is subtriangular in cross-section and unites anteriorly
335 to a minor cusp that, in turn, is united to the anterolingual cingulum, forming a valley or
15
336 fossette in between. The p1 is more complex, as the two cusps are more developed and
337 form a better-defined valley. The anterior crest (paralophid) bifurcates at its end. From the
338 principal cusp, three cristids develop: a more continuous one, lingually directed, and other
339 lower two that direct posterolingually and posterolabially, with a valley in between limited
340 by a basal posterior cingulum. Both teeth present a longitudinal curvature, labially convex.
341 CTES-PZ 3750 (Fig. 2.18) only preserves one of the three teeth complete enough
342 (horizontally broken) to be described, and it is interpreted as the m2. Trigonid and talonid
343 are approximately equal, with deep ectoflexid; the labial wall of trigonid is more rounded
344 than that of talonid; the lingual groove between lobes is transversally less deep than the
345 ectoflexid; the trigonid, in turn, has a lingual groove limiting the rounded metaconid.
346 Comments and comparisons. Neither Álvarez (1978) nor Bond et al. (1998) included the
347 specimen CTES-PZ 3750 in their works. Concerning CTES-PZ 3768, Álvarez (1978)
348 interpreted it as a maxilla with I3–C of an Oldfieldthomasiidae, but Bond et al. (1998)
349 reinterpreted it as a mandibular fragment with canine and p1 of an undetermined
350 Interatheriidae. As teeth are unworn, the comparison with published interatheriines is not
351 easy, but we agree with the latter option, as explained below.
352 Compared with Deseadan specimens published by Vera et al. (2017), the size of
353 CTES-PZ 3768 (Figs. 2.19–20) matches that of the permanent c–p1 of Argyrohyrax
354 proavus (Tab. 2; Vera et al., 2017: tab. 3); in addition, the morphology of the canine is
355 close to the specimen from Oeste de Río Chico (Chubut Province) (Vera et al., 2017: fig.
356 3c) and both the canine and the p1 are similar to the homologous teeth of MCNAM-PV
357 4697 from Quebrada Fiera (Vera et al., 2017: figs. 6b–c). As stated by these authors, A.
358 proavus presents rooted p1–2 and hypsodont p3–m3, which coincides with booth CTES-PZ
359 3768 and CTES-PZ PV 3750. The only specimen of Eopachyrucos ranchoverdensis from
16
360 Uruguay bearing anterior cheek teeth differs from CTES-PZ 3768 in having much simpler
361 canine and p1 (Reguero et al., 2003a: fig. 3). In both cases, the individuals are young and
362 so ontogenetic differences are discarded.
363 The morphology of CTES-PZ 3750 coincides with that described by Vera et al.
364 (2017) for the m1–2 of Argyrohyrax (quadrangular trigonid and subcircular talonid), being
365 different from the Patagonian Progaleopithecus Ameghino, 1904 and Archaeophylus
366 Ameghino, 1897 (Vera et al., 2017: fig. 2), as well as from the Bolivian Brucemacfaddenia
367 boliviensis and Federicoanaya sallaensis Hitz, Billet, & Derryberry, 2008 (Vera et al.,
368 2017: 609). CTES-PZ 3750 (Fig. 2.18, Tab. 2) is similar to the m1–2 from Quebrada Fiera
369 assigned to Argyrohyrax proavus by these authors in both morphology and size (Vera et al.,
370 2017: fig. 6, tab. 3). In contrast, the m2 in CTES-PZ 3750 differs from the m1–2 in the
371 holotype of E. ranchoverdensis (Reguero et al., 2003a: fig. 3) by the more transversally
372 expanded paralophid, the union talonid-trigonid more lingually placed, and the mesio-distal
373 axis of talonid more longitudinally oriented. This difference, however, is not so evident
374 with respect to the specimen MAMC-28 referred to E. ranchoverdensis (Reguero et al.,
375 2003a: fig. 5: the caption corresponds to MAMC-29 figured in fig. 4), which shows more
376 advanced wear and also resembles other material of A. proavus. The size of the molar in
377 CTES-PZ 3750 (Tab. 2) is smaller than m1 and m2 of E. ranchoverdensis. Even though the
378 incompleteness of CTES-PZ 3750 can raise some doubts, we consider it as A. proavus.
379 Family ARCHAEOHYRACIDAE Ameghino, 1897
380 Genus Archaeohyrax Ameghino, 1897
381 Type species. Archaeohyrax patagonicus Ameghino, 1897
382 cf. Archaeohyrax suniensis Billet, Patterson, & Muizon, 2009
383 Figure 3.1–3.2
17
384 Material and origin. Río Corrientes, Perugorría, upper “section”, Curuzú Cuatiá
385 Department: CTES-PZ 3789, right lower premolar, interpreted as a possible p3 or p4.
386 Arroyo María Grande, Perugorría, Curuzú Cuatiá Department, lower “section”: CTES-PZ
387 3772, left mandibular fragment with incomplete m1 or m2 and remnants of following molar
388 inside the alveolus.
389 Description. CTES-PZ 3789 (Fig. 3.1) is a rather worn premolar (p3 or p4?) of
390 Archaeohyracidae, characterized by the great posterior width of the talonid, with respect to
391 the trigonid, and the straight posterior face, which gives a general subtriangular outline; the
392 lingual face of the tooth is well inclined and hardly concave-convex. The labial groove is
393 wide and reaches half of the occlusal surface.
394 The most complete tooth in CTES-PZ 3772 (Fig. 3.2) reveals a young individual as
395 trigonid and talonid are not fused yet; in addition, both lobes seem to preserve remnants of
396 a central fossettid (it would disappear with a little more wear). Despite its bad preservation,
397 the talonid shows a marked posterolingual groove.
398 Comments and comparisons. Álvarez (1978) determined CTES-PZ 3789 as a possible p3
399 of the Hegetotheriidae Propachyrucos Ameghino, 1897; besides, with the same collection
400 number indicated a P3 of the same taxon, but coming from a different locality (Arroyo
401 Ávalos), a tooth not found in the collection. Even though the talonid of CTES-PZ 3789 can
402 be similar in the p3 of hegetotheriids (e.g., P. schiaffinoi from Salla in Cerdeño & Reguero,
403 2015: fig. 5G), the trigonid is different, as it is proportionally longer than in
404 archaeohyracids. One specimen of the hegetotheriid Hegetotheriopsis sulcatus from the
405 early Miocene of Patagonia shows the m1 posterolingually expanded (Kramarz & Paz,
406 2013: fig. 3.2), but differs from CTES-PZ 3789 by the more convex posterior wall, the
407 deeper lingual groove and the proportionally wider trigonid. Instead, the described
18
408 morphology of CTES-PZ 3789 is close to that of worn p4 and m1 (closer to p4 in the
409 outline of trigonid) of Archaeohyrax suniensis from both Salla, Bolivia (Billet et al., 2009:
410 figs. 14C–15) and Quebrada Fiera, Mendoza, Argentina (Cerdeño et al., 2010: fig. 3.2), but
411 CTES-PZ 3789 shows a more acute distolingual corner and a smoothly concave, though
412 generally straighter lingual wall (the latter is straighter in p4 than in m1 of the specimen
413 from Salla). The size, instead, is clearly smaller than that of the p4 and even the p3 of A.
414 suniensis (Tab. 3; Billet et al., 2009: tab. 2a; Cerdeño et al., 2010: tab. 2), which is in turn
415 smaller than the type species A. patagonicus (Billet et al., 2009: 462; fig. 21B: the holotype
416 does not show the morphology described in CTES-PZ 3789). The L/W ratio in CTES-PZ
417 3789 (1.33) is also slightly greater than that of some p3 from Salla (e.g., MNHN-SAL 523,
418 1.19), being closer to that of the p2 MNHN-SAL 310 (1.37) after data from Billet et al.
419 (2009: tab. 2a). However, the p2 of this species does not show so differentiated trigonid and
420 talonid (e.g., Cerdeño et al., 2010: fig. 3.2, 6). The size of CTES-PZ 3789 also closes that
421 of several p3 of the older archaeohyracid Protarchaeohyrax gracilis Roth, 1903 (Reguero
422 et al., 2003b), but the morphology also present some differences as A. suniensis. This lack
423 of morphological match prevents an accurate identification of the tooth, but similarities
424 with the coeval A. suniensis allow us to close CTES-PZ 3789 to this species.
425 CTES-PZ 3772 was previously recognized as Archaeohyracidae by Bond et al.
426 (1998); Álvarez (1978) included it as ?Marcharohyraciidae, but this name might be a typing
427 error. The incompleteness of the specimen does not allow appropriate comparisons, but the
428 morphology of the preserved talonid is close to that of m1 or m2 of young individuals of A.
429 suniensis, although its size (Tab. 3) is close but even smaller than the smallest m1 of this
430 species (e.g., Billet et al., 2009, fig. 17A, tab. 2b); as said above, A. patagonicus is still
431 larger than A. suniensis.
19
432 Based on the stated differences of these specimens with the compared material, we
433 cannot confidently assure their taxonomic assignment and opt for an open determination as
434 cf. Archaeohyrax suniensis.
435 Bond et al. (1998) also recognized CTES-PZ 3756 as an archaeohyracid; however,
436 this specimen is herein recognized as “P.” schiaffinoi (see above). In turn, Perea (2007)
437 indicated that Archaeohyracidae are present in the Uruguayan outcrops of the Fray Bentos
438 Formation with a form identified as “Bryanpattersonia” (= Archaeotypotherium Roth,
439 1903, in Croft et al., 2003; Tinguirirican SALMA), but there is not a detailed description of
440 the assigned material.
441 Family ARCHAEOHYRACIDAE?
442 Figure 3.3
443 Material and origin. Arroyo María Grande, Perugorría, Curuzú Cuatiá Department, lower
444 “section”: CTES-PZ 3778, mandibular fragment, horizontally broken, with symphysis and
445 remains of left p1–p4 and right p2.
446 Description. The left series preserved in CTES-PZ 3778 (Fig. 3.3) shows a first tooth with
447 subcircular-suboval section, which we interpret as the p1; it is followed by other two
448 premolars, p2 and p3, which show the trigonid much more developed than the talonid.
449 These premolars have a subelliptic trigonid, anteriorly rounded, whereas the talonid is
450 subtriangular, much shorter than the trigonid (the latter almost doubles the former); the
451 labial groove between lobes is deep, more open in p2 than in p3, in which the talonid
452 becomes relatively wider; on the lingual face, there is a smooth concavity opposite to the
453 labial groove (better observed in p3). The teeth are not aligned but obliquely implanted
454 with respect to the axis of the mandibular ramus; however, there is no imbrication, because
20
455 they are separated by diastemas (just p2 reaches the level of p1). The horizontal rami
456 diverge from the symphysis at a great angle, around 70º.
457 Comments and comparisons. CTES-PZ 3778 was considered by Álvarez (1978) as a
458 Hegetotheriidae, while this material was not studied by Bond et al. (1998); in turn, Reguero
459 (1999: tab. 5.19) mentioned this specimen as Leontiniidae?. However, the morphology of
460 the preserved tooth remains in CTES-PZ 3778 does not correspond to a hegetotheriid, as
461 the described difference between trigonid and talonid does not occur in the p3 of
462 hegetotheriids and not so markedly in the p2. This strong differentiation occurs instead in
463 worn premolars of Archaeohyracidae. Particularly, the tooth morphology in CTES-PZ 3778
464 is roughly comparable, for instance, to Protarchaeohyrax gracilis Reguero, Croft, Flynn, &
465 Wyss, 2003b from Tinguiririca (Chile; see Reguero et al., 2003b: fig.2) or Archaeorhyrax
466 suniensis from Salla (Bolivia; see Billet et al., 2009: figs. 14C–15), mainly in the p1 and
467 p3. Within the archaeohyracid sample from Quebrada Fiera (Mendoza), mostly identified
468 as A. suniensis, few specimens preserve the anterior premolars; in MCNAM-PV 3844, the
469 most similar tooth is the suboval p1, but p2 has a poorly developed talonid and p3 does not
470 show a clear difference between lobes (Cerdeño et al., 2010: fig. 3.5). The size of CTES-PZ
471 3778 (Tab. 3) results small compared with A. suniensis from both localities, as well as
472 compared with the previous specimen CTES-PZ 3789, even considering that they are not
473 homologous teeth. In any case, the most striking difference of CTES-PZ 3778 is the
474 oblique position of premolars, while teeth are aligned in the compared archaeohyracids;
475 besides, this obliquity is not accompanied by the imbrication of teeth (what happens in
476 some hegetotheriids, for instance). It is evident that we would need more material from
477 Fray Bentos Formation to reach a more confident determination, but based on the tooth
478 morphology, CTES-PZ 3778 could belong to Archaeohyracidae.
21
479 Family “NOTOHIPPIDAE” Ameghino, 1894a
480 Genus Mendozahippus Cerdeño & Vera, 2010
481 Type species. Mendozahippus fierensis Cerdeño & Vera, 2010
482 cf. Mendozahippus fierensis Cerdeño & Vera, 2010
483 Figure 3.4
484 Material and origin. Arroyo María Grande, Perugorría, Curuzú Cuatiá Department, lower
485 “section”: CTES-PZ 3788, right maxillary fragment with three fractured and incomplete
486 teeth, interpreted as P4–M2.
487 Description. We interpret CTES-PZ 3788 as the upper dentition, P4–M2, of a
488 “Notohippidae” after comparison with the Deseadan species from Quebrada Fiera
489 (Mendoza), Mendozahippus fierensis (Cerdeño & Vera, 2010, 2014). Teeth present an
490 advanced wear stage and are badly preserved. The incomplete labial faces show relatively
491 high crowns; in the occlusal surface, an elongate fossette is observed, more oblique in M2;
492 the ectoloph is rather straight, although there is a smooth concavity in M1.
493 Comments and comparisons. CTES-PZ 3788 was identified by Álvarez (1978) as P2–4 of
494 Leontiniidae, and later reinterpreted by Bond et al. (1998) as the deciduous premolars,
495 DP2–4, assigned with doubts to this family. These authors based their interpretation on a
496 cavity present below the supposed DP4 and an erupting tooth behind DP4. In our opinion,
497 they are not deciduous teeth, because in such a case and with their wear stage, the M1
498 would be already in use and well-worn, not erupting; besides, the specimen shows
499 fragments of roots of the interpreted M2 (there is no cavity below it) and small remains of
500 the M3. Instead, the morphology of these teeth strongly resembles that of P4–M2 of
501 Mendozahippus fierensis, especially with well-worn specimens such as MCNAM-PV 4370
502 and MCNAM-PV 4371 (Cerdeño & Vera, 2014: fig.1A–B), but not so extreme as in the
22
503 holotype (Cerdeño & Vera, 2010: fig. 2C); as wear advances, teeth increase in width and
504 the outline becomes more rectangular, but in CTES-PZ 3788 it is still rather square.
505 Dimensions of CTES-PZ 3788 (Tab. 4) better fit P4–M2 than P3–M1 of M. fierensis
506 whereas they are much smaller than those of the leontiniid Gualta cuyana Cerdeño & Vera,
507 2015, from Quebrada Fiera.
508 The partial condition of CTES-PZ 3788 does not allow unquestionably assuring that
509 it belongs to M. fierensis, as the morphology of the cheek teeth are similar in other
510 Deseadan species of this group. The Bolivian taxa from Salla, Eurygenium pacegnum
511 Shockey, 1997 and Pascualihippus boliviensis Shockey, 1997, are larger forms. The
512 notohippid from Peru, Moqueguahippus glycisma Shockey et al., 2006, is known by a
513 fragmented mandible (so not comparable with CTES-PZ 3788), which differs from
514 Mendozahippus (Cerdeño & Vera, 2014). Rhynchippus brasiliensis Soria & Alvarenga,
515 1989, from the Tremembé Formation (Brazil) resembles the Patagonian species
516 Rhynchippus equinus Ameghino, 1897 (see Marani & Dozo, 2008) but lower teeth (the
517 referred P4 was not figured) seem to be also similar to M. fierensis. Among the species
518 from Patagonia, CTES-PZ 3788 is smaller than Rhynchippus equinus and Eurygenium
519 latirostris Ameghino, 1894b (Marani, 2005: table 2; Marani and Dozo, 2008: table 3) and
520 larger than R. pumilus Ameghino, 1897 (Chaffee, 1952). In turn, Argyrohippus praecox
521 Patterson, 1935 differs from CTES-PZ 3788 in having a cup-like posterolingual cingulum
522 in P2–4 and thick layer of cement. Therefore, it is evident that the closer affinity of CTES-
523 PZ 3788 is with M. fierensis, both in morphology and size, despite which we maintain the
524 open nomenclature cf. M. fierensis until new material can better support its identification
525 with the taxon from Mendoza.
23
526 Previously, neither Álvarez (1978) nor Bond et al. (1998) had recorded the presence
527 of notohippids in the Fray Bentos Formation in Corrientes Province. Instead, it was
528 mentioned for the levels cropping out in Uruguay (Kraglievich, 1932; Ubilla et al., 1994),
529 but without further details on the material assigned to this group, which could provide more
530 data to contrast our determination. Notohippids do not constitute a natural group of
531 notoungulates in the phylogenetic analyses (e.g., Shockey, 1997; Cerdeño & Vera, 2010;
532 Deraco & García López, 2016).
533 Family LEONTINIIDAE Ameghino, 1894b
534 Leontiniidae indet.
535 Figure 3.5
536 Material and origin. Río Corrientes, Perugorría, Curuzú Cuatiá Department: CTES-PZ
537 7871, left mandibular fragment with remains of m1–2.
538 Description. The anterior tooth (talonid of m1) in CTES-PZ 7871 is badly preserved and
539 only shows the presence of two lingual grooves. The m2 is more complete, but altered in
540 the occlusal surface. It shows a shallow ectoflexid behind a marked angle on the trigonid
541 wall; lingually, there is an anterior groove at the level of the labial angle; the metaconid is
542 wide, posteriorly directed and limits a deep meta-entoconid groove, slightly mesiolabially
543 oriented; this groove is still open, without forming a fossettid, which would appear with
544 more wear; more posteriorly placed, the ento-hypoconid groove is transversally shorter (the
545 area is eroded); in addition, there is a central (or accessory) fossettid in the talonid.
546 Comments and comparisons. The morphological features of CTES-PZ 7871 resemble the
547 m1–2 of the leontiniids Scarrittia robusta Ubilla, Perea, & Bond, 1994, from the Fray
548 Bentos Formation in Uruguay (Ubilla et al., 1994: fig. 3), and Gualta cuyana from
549 Quebrada Fiera (Cerdeño & Vera, 2015: fig. 6B). However, dimensions of CTES-PZ 7871
24
550 are well below those of both species, even comparing with a juvenile individual (Tab. 5;
551 Ubilla et al., 1994; Cerdeño & Vera, 2015). It is also smaller than the Patagonian
552 Elmerriggsia fieldia Shockey et al., 2012, a species smaller than Scarrittia Simpson, 1934,
553 and Leontinia Ameghino, 1894b, which does not present the angled trigonid or the
554 posterolingual groove (Shockey et al., 2012: fig. 6). More similar in size is the lower molar
555 of Henricofilholia lustrata Ameghino, 1901 (dimensions, 27 mm × 12 mm after Ameghino,
556 1901) from the Sarmiento Formation, in which the lingual wall of the talonid is more
557 convex and the trigonid less angled than in CTES-PZ 7871 (see Ribeiro et al., 2010: fig.
558 11.4.B).
559 On the other hand, CTES-PZ 7871 is larger than notohippids, for instance M.
560 fierensis (Cerdeño & Vera, 2010, 2014), from which it also differs by the labially angled
561 trigonid and the wide ectoflexid.
562 Álvarez (1978) included in Leontiniidae the specimens CTES-PZ 3788, CTES-PZ
563 3770, and CTES-PZ 3776, neither of which are herein recognized as such; the former is a
564 notohippid (see above) and the other two cannot be properly determined (see below). Bond
565 et al. (1998) also considered CTES-PZ 3788 and CTES-PZ 3770 as leontiniids, but with a
566 different anatomical interpretation. Now, CTES-PZ 7871 allows us to maintain the
567 presence of leontiniids in the Fray Bentos Formation in Corrientes Province, but we cannot
568 assure to which genus it belongs.
569 NOTOUNGULATA INDET. 1
570 Figure 3.6
571 Material and origin. Río Corrientes, Perugorría, Curuzú Cuatiá Department: CTES-PZ
572 3762, distal fragment of metapodial: articular transversal diameter = 5.80 mm; articular
25
573 anteroposterior diameter = 4.4 mm; transversal diameter of the diaphysis at breakage level=
574 3.79 mm.
575 Description and comparisons. The metapodial fragment is rather symmetric, with the
576 lateral epicondyle more salient than the entepicondyle; there is a smooth keel on the
577 posterior area of the trochlea. It likely corresponds to the third digit. Its small dimensions
578 match with a hegetotheriid of the size of “P.” schiaffinoi (e.g., Reguero & Cerdeño, 2005:
579 fig. 5D). Quebrada Fiera has provided some metapodials with the same size and
580 morphology (e.g., MCNAM-PV 4577, EC personal data), but they have not been assigned
581 so far to a particular group of notoungulates.
582 NOTOUNGULATA INDET. 2
583 Figure 3.7
584 Material and origin. Arroyo María Grande, Perugorría, Curuzú Cuatiá Department, lower
585 “section”: CTES-PZ 3776, left mandibular fragment with root remains of several cheek
586 teeth and a large incisor.
587 Description. CTES-PZ 3776 catches the attention by the most anterior preserved root
588 (maybe corresponding to the i2), much larger than the others, and with a roughly L-shaped
589 outline, but with the inflexion on the labial wall. This root is almost transversally placed
590 with respect to the cheek-tooth series; its lingual face is smoothly concave-convex whereas
591 the labial face shows a strong inflexion, in such a way that the root is clearly wider on the
592 outer side. The two following roots are small, mainly the most anterior one, and could
593 correspond to reduced i3 and canine.
594 Comments and comparisons. Álvarez (1978) attributed this specimen to a Leontiniidae
595 indeterminate, but Bond et al. (1998) recognized it as an undetermined mesotheriid
596 Trachytheriinae, bearing roots of i2–3, c, p1 and part of p2. Later, Reguero (1999) and
26
597 Reguero & Castro (2004) considered CTES-PZ 3776 as probably belonging to the
598 trachytheriine Trachytherus curuzucuatiense (Podestá, 1899). This species, coming from
599 the Fray Bentos Formation in Corrientes Province, was initially described as
600 Ameghinotherium curuzucuatiense Podestá, 1899, from a cranial fragment, but Billet et al.
601 (2008) considered it a synonym of Trachytherus spegazzinianus Ameghino, 1889.
602 The striking outline of the most anterior root in CTES-PZ 3776 does not coincide
603 with the i2 of the mentioned families, even though the general size and position of roots are
604 closer to trachytheriines (Billet et al., 2008) than to leontiniids. In contrast, the i2 in
605 Trachytherus Ameghino, 1889 (only valid genus of Trachytheriinae) has a well-marked
606 lingual groove in little worn teeth (Billet et al., 2008: 169, figs. 7, 14, 17). The implantation
607 of i2 in CTES-PZ 3776 is more vertical than in T. alloxus Billet, Muizon, and Mamaní
608 Quispe, 2008, from Salla, although not so different from that of T. spegazzinianus (Billet et
609 al., 2008: figs. 7 and 17). According to these authors, the two following roots would agree
610 with the vestigial i3 and canine (the latter would be present only in juvenile individuals) of
611 T. alloxus. But in any case, the i2 section does not match trachytheriines.
612 Notoungulates with L-shaped cross section and more transversal position of incisors
613 are the Toxodontidae, but the outline in CTES-PZ 3776 is almost contrary to that of the
614 incisors in toxodontids, because the latter have a lingual (not labial) inflexion (e.g., Scott,
615 1912). Proadinotherium saltoni Shockey and Anaya, 2008, from Salla was described based
616 on an almost complete mandible. This specimen preserves the three pairs of incisors, the i3
617 rather transversely placed, but with a lingual groove; the symphysis enlarges at the level of
618 i3 in such a way that they laterally overpass the axis of the horizontal ramus, which also
619 happens in CTES-PZ 3776. In P. saltoni, i3 is followed by reduced canine and p1, without
620 diastema in between (in contrast to P. leptognathum Ameghino, 1894b, from Patagonia).
27
621 The length of i3 of P. saltoni (around 13 mm; Shockey & Anaya, 2008: Appendix) is
622 similar to the anteriormost root in CTES-PZ 3776, but its width (4.6 mm) is much lesser,
623 maybe due to the fact that the individual of P. saltoni is still young (m2–3 little worn).
624 From Quebrada Fiera, toxodontid remains identified as Proadinotherium sp. are scarce and
625 not homologous (Hernández Del Pino et al., 2017).
626 NOTOUNGULATA INDET. 3
627 Figure 3.8–3.9
628 Material and origin. Arroyo María Grande, Perugorría, Department Curuzú Cuatiá, lower
629 “section”: CTES-PZ 3770, maxillary fragment with three badly preserved teeth.
630 Description and comments. In our opinion, CTES-PZ 3770 corresponds to the upper
631 dentition, but it is difficult to assess which teeth are present. Only one tooth allows seeing
632 an enamel fold and what could be a well-developed anterolingual cingulum. Álvarez (1978)
633 recognized CTES-PZ 3770 as a mandibular fragment of Leontiniidae, with canine and p1;
634 on the contrary, Bond et al. (1998) interpreted it as a maxillary fragment of Leontiniidae
635 indet., with I1–3 or I2–C. The mentioned morphology fits better with an upper premolar
636 than with a canine or incisor; however, it does not fit with upper premolars of leontiniids,
637 because the latter present an anteriorly open central fossette (e.g., Cerdeño & Vera, 2015:
638 fig. 5). The size of this tooth is (11.6) mm × (8.8) mm; the other more complete tooth,
639 anteriorly positioned, is slightly larger: (13.4) mm × (10.6) mm. These values are close but
640 smaller than those of the anterior upper teeth of Gualta cuyana (Cerdeño & Vera, 2015:
641 tab. 2); the leontiniid from Uruguay, Scarrittia robusta, is only known by lower teeth. At
642 present, we cannot identify the specimen CTES-PZ 3770 and consider it as an
643 undetermined large notoungulate.
644 CONCLUSIONS
28
645 In the framework of new research on the Fray Bentos Formation in Corrientes
646 Province, we perform a revision of the old collected material assigned to the Order
647 Notoungulata, together with a few new specimens. This study allows us to precise in most
648 cases the anatomical and/or taxonomical determinations, although others cannot be
649 confidently identified (Table 6). Recognized taxa are one Hegetotheriidae, two
650 Interatheriidae, one Archaeohyracidae, one “Notohippidae”, and one Leontiniidae, as well
651 as some undetermined specimens. Among them, it seems possible that the upper premolars
652 identified as an undetermined interatheriid could represent the unknown upper teeth of
653 Eopachyrucos ranchoverdensis, a species defined in the Fray Bentos Formation in Uruguay
654 based on three mandibular fragments. Another important result is the recognition of a
655 notohippid very similar to Mendozahippus fierensis, a species so far only known from
656 Quebrada Fiera (Mendoza Province). Similarly, cf. Archaeohyrax suniensis
657 (Archaeohyracidae) and “Prohegetotherium” schiaffinoi (Hegetotheriidae) establish
658 affinities with both Salla (Bolivia) and Quebrada Fiera. Similitudes with Salla were also
659 established from the xenarthran remains from the Fray Bentos Formation in Corrientes
660 (Carlini et al., 2007). At the same time, other taxa are shared with Patagonian Deseadan
661 faunas, such it is the case of Argyrohyrax proavus (Interatheriidae) or Trachytherus
662 spegazzinianus (the mesotheriid Trachytheriinae identified from material not studied
663 herein; see above). This situation also happens in the two mentioned localities, in which
664 Patagonian taxa are present together with so far exclusive genera/species. Concerning the
665 latter, the recognition of cf. M. fierensis in Corrientes Province is important from a
666 paleobiogeographic point of view, as it would reveal the expansion of up-to-now exclusive
667 taxa from Mendoza Province to the east. We hope that new findings from the Fray Bentos
668 Formation in Corrientes Province can help to reach more confident determinations and thus
29
669 to precise the faunal affinities with higher (Patagonia) and lower (e.g., Mendoza, Salla)
670 latitudes during the Deseadan SALMA.
671 ACKNOWLEDGMENTS
672 The authors acknowledge A. Kramarz and D. García-López, as well as the editorial staff,
673 for their useful suggestions to improve the manuscript. Thanks are also due to F. Seoane, B.
674 Vera, M.E. Pérez and M. Reguero for helpful discussions on the taxonomy of several
675 specimens; to C.M. Vega, who made some of the presented photographs, to J. González
676 who made the line drawing, and to H. Smichowsky for drawing the location map. This
677 paper contributes to the research projects ANPCyT-PICT 2017-0765, SGCYT-UNNE PI
678 18/Q002, PI 17/Q002, and PUE-CONICET 229 20180100001 CO Argentina.
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881 FIGURE CAPTIONS
882 Figure 1. Geographical location of the Fray Bentos Formation localities in Argentina and
883 Uruguay. 1. Río Corrientes; 2. Arroyo María Grande; 3. Arroyo Ávalos; 4. Curuzú Cuatiá;
884 5. Chajarí; 6. Colón; 7. Playa de la Agraciada; 8. Paso del Cuello (after Ubilla et al., 1994;
885 Bond et al., 1998; Perea et al., 2014).
886 Figure 2. “Prohegetotherium” schiaffinoi, 1–2. CTES-PZ 3744, right mandibular
887 fragment with m3 (occlusal and labial views); 3–4. CTES-PZ 3748-CTES-PZ 3749, right
888 mandibular fragments with p3–m2 and m3, respectively, from the same individual (occlusal
889 and labial views); 5–6. CTES-PZ 3751, left mandibular fragment with m1–3 (occlusal and
890 labial views); 7–8. CTES-PZ 3755, left mandibular fragment with p3–4 (occlusal and labial
891 views); 9–10. CTES-PZ 3756, right mandibular fragment with p4–m1 (occlusal and labial
892 views); 11–12. CTES-PZ 3766, right upper molar (M1) (occlusal and lingual views); 13–
893 14. CTES-PZ 3767, right upper premolar (P4) (occlusal and lingual views); 15–16. CTES-
894 PZ 7872, left mandibular fragment with p3–m3 (occlusal and labial views).
895 Interatheriidae indet., 17. CTES-PZ 3775, right maxillary fragment with P3–4 (occlusal
896 view and scheme). Argyrohyrax proavus, 18. CTES-PZ 3750, left mandibular fragment
897 with remains of three teeth (m1–3?) (occlusal view); 19–20. CTES-PZ 3768, right
898 mandibular fragment with c–p1 (occlusal and lingual views). Abbreviations: fos, fossette;
899 pa, paracone fold; par, parastyle. Scale bars: 5 mm.
39
900 Figure 3. cf. Archaeohyrax suniensis, 1. CTES-PZ 3789, right lower premolar (p3?,
901 occlusal view); 2. CTES-PZ 3772, left mandibular fragment with incomplete m1 or m2 and
902 remnants of another molar inside the alveolus (occlusal view); Archaeohyracidae?, 3.
903 CTES-PZ 3778, mandibular fragment, transversally broken, with symphysis and remains of
904 left p1–p4 and right p2 (occlusal view); cf. Mendozahippus fierensis, 4. CTES-PZ 3788,
905 right maxillary fragment with three fractured and incomplete teeth, interpreted as P4–M2
906 (occlusal view and scheme); Leontiniidae indet., 5. CTES-PZ 7871: left mandibular
907 fragment with remains of m1–2 (occlusal view); Notoungulata indet. 1, 6. CTES-PZ 3762,
908 distal fragment of metapodial (posterior and lateral views); Notoungulata indet. 2, 7.
909 CTES-PZ 3776, left mandibular fragment with root remains of several cheek teeth and a
910 large incisor (occlusal view); Notoungulata indet. 3, 8–9. CTES-PZ 3770, partial maxilla
911 with I1–2 and C, or I2, C, and P1 (labial and occlusal views). Scale bars: 1–3: 5 mm, 4–8
912 and 9: 10 mm.
913 TABLE CAPTIONS (included with explanations in each table)
914 Table 1. Tooth dimensions (mm) of “Prohegetotherium” schiaffinoi (Hegetotheriidae) from
915 Fray Bentos Formation, Corrientes Province.
916 Table 2. Comparative tooth dimensions (mm) of Interatheriidae from the Fray Bentos
917 Formation, Corrientes Province.
918 Table 3. Comparative tooth dimensions (mm) of Archaeohyracidae from the Fray Bentos
919 Formation, Corrientes Province.
920 Table 4. Upper tooth dimensions (mm) of Notohippidae from the Fray Bentos Formation,
921 Corrientes Province, compared with notohippid (Mendozahippus fierensis) and leontiniid
922 (Gualta cuyana) specimens from Quebrada Fiera, Mendoza Province.
40
923 Table 5. Comparative lower tooth dimensions (mm) of Leontiniidae from the Fray Bentos
924 Formation, Corrientes Province.
925 Table 6. Comparison of the taxonomic determinations of the studied notoungulate material
926 from the Fray Bentos Formation, Corrientes Province.
41
TABLE 1 – Tooth dimensions (mm) of “Prohegetotherium” schiaffinoi (Hegetotheriidae) from Fray Bentos
Formation, Corrientes Province.
p3 p4 m1 m2 m3
L W L W L W L W L W
CTES-PZ 3751 4.7 2.8 5.2 >2.3 - >1.8
CTES-PZ 3755 3.8 2.7 (4.3)(2.8)
CTES-PZ 3748–49 4.0 2.4 5.0 2.9 7.0 3.1 >4.7 2.7 7.2 3.1
CTES-PZ 3744 6.0 2.6
CTES-PZ 7872 3.1 1.8 3.6 2.1 4.6 2.7 4.0 2.5 (5.4) (2.2)
CTES-PZ 3756 3.0 1.5 4.0 3.1
P4 M1
L A L A
CTES-PZ 3766 6.5 3.9
CTES-PZ 3767 4.8 3.6
Approximate values in parentheses. See abbreviations in text.
TABLE 2 – Comparative tooth dimensions (mm) of Interatheriidae from Fray Bentos Formation, Corrientes
Province.
P3 P4
L W L W
Indet.
CTES-PZ 3775* 5.6 3.7 >5 (4.4)
A. proavus
MCNAM-PV 3967 1 7.2 5.8 7.2 5.6
MCNAM-PV 4233 1 6.5 4.2 6.5 4.3
c p1 p2 m1 m2 m3
L W L W L W L W L W L W
A. proavus
CTES-PZ 3750 5.6 3.8
CTES-PZ 3768 3.5 2.3 5.4 2.5
MCNAM-PV 4697 1 4.7 2.4 5.7 3.1 6.4 4.2 6.6 4.2 8.1 3.3
E. ranchoverdensis 2
MAMC-39 4.8 2.4 5.9 3.2 8.7 4.5 7.9 5.2
MAMC-29 6.4 4.0 6.6 4.0 5.9 3.4
MAMC-28 7.9 4.6 7.6 3.4
E. pliciferus 3
MLP 12-1529 4.1 1.6 4.1 1.9 4.1 2.5 – – 5.3 2.5
*Approximate values. 1 After Vera et al. (2017), specimens from Quebrada Fiera, Mendoza Province; 2after
Reguero et al . (2003a), from the Fray Bentos Formation, Uruguay; 3after Hitz et al . (2000), from Gran
Barranca, Chubut Province. See abbreviations in text.
TABLE 3 – Comparative tooth dimensions (mm) of Archaeohyracidae from Fray Bentos Formation,
Corrientes Province.
p1 p2 p3 p4 m1 m2
L W L W L W L W L W L W cf. A. suniensis
CTES-PZ 3789 4.0. 3.0
CTES-PZ 3772 6.1 2.8
A. suniensis 1
MCNAM-PV 3844 4.0 3.1 (5.5) 3.7
MLP 77-VI-1-1 6.1 4.4 7.5 4.7
MCNAM-PV 3954 7.1 4.4
Archaeohyracidae?
CTES-PZ 3778 left 0.8 0.5 2.3 1.0 2.7 (1.4)
right 2.6 1.0
1After Cerdeño et al . (2010: tab. 2), specimens from Quebrada Fiera, Mendoza Province. Approximate values in parentheses. See abbreviations in text.
TABLE 4 – Upper tooth dimensions (mm) of Notohippidae from the Fray Bentos Formation, Corrientes
Province, compared with notohippid ( Mendozahippus fierensis ) and leontiniid ( Gualta cuyana ) specimens from Quebrada Fiera, Mendoza Province.
P3 P4 M1 M2
L W L W L W L W cf. M. fierensis
CTES-PZ 3788 (10.0) 12.4 14.2 16.3 20.1 20.9
M. fierensis 1
MCNAM-PV 4004 left 9.4 13.8 11.0 17.0 14.1 20.0 22.1 22.9
right (9.0) 13.6 (12.3) 17.7 <16 <23 (20.0) 21.5
MCNAM-PV 3846 left 9.3 10.1 11.2 12.0
right 9.3 10.0 – –
MCNAM-PV 4370 13.3 15.2 17.9 18.3 22.0 19.6
MCNAM-PV 4371 9.9 15.6 – – (12.4)(17.0) 19.3 23.3
Gualta cuyana 2
MCNAM-PV 3951 left 21.4 33.7 23.3 34.6 31.4 36.4 43.7 44.4
right 20.6 30.6 22.9 34.4 33.0 37.3 45.2 44.2
1After Cerdeño & Vera (2010, 2014); 2after Cerdeño & Vera (2015). Approximate values in parentheses. See abbreviations in text.
TABLE 5 – Comparative lower tooth dimensions
(mm) of Leontiniidae from the Fray Bentos
Formation, Corrientes Province.
m1 m2
L W L W
CTES-PZ 7871 - 9.8 27.4 10.9
Scarrittia robusta 1
FC-DPV-661 35.2 20.0 48.2 18.7
Gualta cuyana 2
MCNAM-PV 3841 35.5 23.0 (42.2) 22.6
MLP 96-XI-20-3* left 38.6 17.8 44.7 (11.2)
right 39.8 18.9 46.7 (13.0)
1After Ubilla et al . (1994), specimens from the Fray
Bentos Formation, Uruguay; 2after Cerdeño & Vera
(2015), from Quebrada Fiera, Mendoza
Province.*juvenile individual; approximate values in parentheses. See abbreviations in text.
TABLE 6 - Comparison of the taxonomic determinations of the studied notoungulate material from Fray Bentos
Formation, Corrientes Province.
CTES-PZ Álvarez (1978) Bond et al. (1998) This paper
3744 Prohegetotherium sp. Prohegetotherium sp. “Prohegetotherium” schiaffinoi RC (1) (2) (3)
3748 + 3749 Prohegetotherium sp. Prohegetotherium sp. “P.” schiaffinoi RC
3751 Propachyrucos sp. --- “P.” schiaffinoi RC
3755 Propachyrucos sp. Prohegetotherium sp. “P.” schiaffinoi AA
3756 Propachyrucos sp. Archaeohyracidae “P.” schiaffinoi AA
3766 Propachyrucos sp. Prohegetotherium sp. “P.” schiaffinoi AA
3767 Propachyrucos sp. Prohegetotherium sp. “P.” schiaffinoi AA
7872 ------“P.” schiaffinoi RC
3750 ------Argyrohyrax proavus ; RC
3768 Oldfieldthomasiidae Interatheriinae Argyrohyrax proavus ; AMG; (2) (4)
3775 --- Plagiarthrus sp. Interatheriidae indet. ( possible Eopachyrucos
ranchoverdensis ? (1) ); AMG
3772 ?Marcharohyraciidae Archaeohyracidae cf. Archaeohyrax suniensis AMG
3789* Propachyrucos sp. (p3) --- cf. Archaeohyrax suniensis ; RC; (2) (3)
3778** Hegetotheriidae --- Archaeohyracidae? AMG
3788 Leontiniidae (P2–4) Leontiniidae? (DP2–4) cf. Mendozahippus fierensis (P4–M2); AMG; (2)
7871 ------Leontiniidae indet. (m1-2); RC
3762 ------Notoungulata indet. 1 (metapodial); RC 3770 Leontiniidae (mandible) Leontiniidae (maxilla) Notoungulata indet. 3 (maxilla); AMG
3776*** Leontiniidae Thrachytheriinae indet. Notoungulata indet. 2; AMG
*Same number for two isolated teeth, p3 and P3, after Álvarez (1978); ** as Leontiniidae in Reguero (1999); ***as probable Trachytherus curuzucuatiense in Reguero & castro (2004). AA , Arroyo Ávalos; AMG , Arroyo María Grande;
RC , Río Corrientes. (1) Present in the Fray Bentos Formation, Uruguay; (2) present at Quebrada Fiera, Mendoza
Province, Argentina; (3) present at Salla, Bolivia; (4) present at Patagonian localities.