First record of Banderomys leanzai Kramarz, 2005 (Rodentia, Caviomorpha) in Chubut Province, Patagonia (Argentina)

Cephalomyidae was established in the �I� century, and was considered by different authors as a heterogeneous group of hypsodont South American hystricognath rodents. Other authors corroborated this family as a natural group among caviomorphs and recognized some taxa recorded from the Deseadan–Colhuehuapian South American Land Mammals Ages (SALMAs). Among them, Banderomys leanzai (the only species of this genus) was, until now, characteristic and exclusive of the locality of Cerro Bandera (early Miocene, Colhuehuapian?, Neuquén Province, Argentina). The aim of this work is to report the first record of B. leanzai outside the type locality; the new specimens come from the early Miocene of central Chubut Province (Patagonia, Argentina). This new finding extends the geographical distribution of the species and increases the dental morphology knowledge of B. leanzai.

Banderomys leanzai Kramarz (2005), the only species of this genus, was originally described from Cerro Bandera (Neuquén province, Argentina; Fig. 1), initially considered early Miocene in age (Colhuehuapian?SALMA, but see Kramarz et al., 2011Kramarz et al., , 2013Kramarz et al., , 2015)).B. leanzai is currently represented by scarce registers, including a poorly preserved mandible fragment, and some isolated teeth.Here, we report the first specimens of B. leanzai outside Cerro Bandera coming from a new locality in Chubut Province (Fig. 1).In addition, new dental material unknown for this species until now, provide a more complete knowledge of Banderomys enlarging the morphological information to future phylogenetic analysis.

Dental nomenclature and abbreviations
Dental nomenclature used here follows Arnal & Vucetich (2015)

Material for comparison
For taxonomic determination, we conducted an extensive bibliographic revision, and the new specimens were compared with materials housed at PVPH and MOZ-PV, listed in Supplementary Data.The measurements of the new specimens were obtained using a digital caliper with an accuracy of 0.01mm (Table 1).and Colhuehuapian (circles) Patagonian localities that share caviomorphs with Cerro Bandera locality: 1, La Flecha; 2, Cabeza Blanca; 3, Gran Barranca; 4, La Estrella; 5, Bryn Gwyn; 6, Cerro Bandera GEOLOGICAL SETTING Fossil material described here proceed from "La Estrella" (S 44°35'36.60'';W 69° 5'47.90''),named after its proximity (around 3 km in westeast direction) to the homonymous ranch, is located in the western part of the Meseta del Canquel, central Chubut Province, Argentina (Fig. 1) (see also Novo et al., 2017: figure 1).The rocks bearing the herein reported teeth belong to the Sarmiento Formation.The section characterizes by around 18 m of a monotonous succession of mostly massive, fine tuffs, ranging in color from pinkish grey, in the lower section, to greyish, in the top.The fossiliferous section overlies basalts cropping out in the middle section of Meseta del Canquel (e.g.Scarritt Pocket), indicating a post-Deseadan age (Marshall et al., 1986;Vucetich et al., 2014), and underlies a basalt located toward the top of Meseta del Canquel, assigned by Marshall et al. (1986) to the lower Miocene.This stratigraphic position and similarities in lithological features recognized in La Estrella as well as in Gran Barranca (Spalletti & Mazzoni, 1979) allow assigning the study section to the Colhué Huapí Member.

Geographic and stratigraphic provenance.
The new specimens come from La Estrella locality (Sarmiento Formation, Chubut Province, Argentina).All the material listed in Kramarz, 2005 (p. 252)

Description and comparison
The new specimens consist in isolated lower and upper teeth (Figs. 2, 3).The entire sample is assigned here to Banderomys leanzai, because the teeth share the combination of dental characters in the diagnosis for this species.Regarding general characteristics, the molariforms are protohypsodont, with crowns lower than Cephalomys, lack cement, and the enamel is continuous around the entire crown.The lower and upper dental series show an asymmetrical pattern, and with moderate wear, the occlusal surface becomes tetralophodont (Figs.2A, B and see Kramarz, 2005).The upper molars have three roots, a large lingually and two smaller labially, like in Cephalomys and Soriamys.None of the lower molars preserved the roots in the new sample from Chubut.
Upper molars.Among the upper teeth in the new sample, there are three M1 or M2 (Figs. 2A-C and 3A-C); all of them show unilateral hypsodonty.The MPEF-PV 10966a is a left M1 or M2 (Figs. 2A, 3A) with moderate stage of wear, the tooth appears to be tetralophodont but the posterior portion is broken and this cannot be corroborated.The hypoflexus is transversely short, V-shaped, and antero-posteriorly oriented, with the tip next to the paraflexus.The paraflexus and mesoflexus remain open, being the latter the deepest.These flexi are long and straight, wider labially, extending over the middle of the occlusal surface, and their lingual tips are slightly rounded.The only closed labial flexus is forming the metafossette, the anterior margin is relatively straight, and the lingual border is rounded.The postero-labial angle of the tooth is slightly broken and it is impossible to determine whether the posterofossette is present, although in this stage of wear, is usually present in the specimens from Cerro Bandera.The anterior margin of the anteroloph is straight and curved posteriorly at the lingual extreme.Thus, the protocone area is acute, while the hypocone area is more rounded and slightly more labial than the former.The anteroloph and protoloph are relatively straight; the mesolophule is curved postero-labially, and is probably joined to the metaloph.
The MPEF-PV 10966b is a right M1 or M2 (Figs. 2B, 3B) a little more worn than MPEF-PV 10966a; at this stage of wear it is clearly tetralophodont with the three labial fossettes completely close, and the posterofossette is absent.The hypoflexus is longer than in MPEF-PV 10966a, transversely extending almost up to the middle portion of the occlusal surface.It is V-shaped with the lingual tip acute, near the parafossette.The fossettes are transversely elongated, especially the mesofossette.The anteroloph is curved, protoloph and mesolophule are relatively straight, and the posteroloph present a widening at its labial end.In this stage of wear, the protocone and hypocone areas are more triangular in outline than in MPEF-PV 10966a, and they are mesio-distally aligned.
MPEF-PV 10966c is a right M1 or M2 (Figs. 2C, 3C), showing a more advanced stage of wear even than MPEF-PV 10966b; it is broken with the posterior and labial portions missing.The hypoflexus is longer than in the other upper teeth of the sample.It is quadrangular at the labial extreme.It is slightly oblique, and almost contacts the parafossette.Only the lingual portion of the parafossette and the mesofossette are preserved, and they are rounded.The protocone area is rounded.
Lower molars.The lower teeth are represented by a m1 or m2 and the first m3 reported for B. leanzai (Figs.2D-E, 3D-E).MPEF-PV 10966d is a left m1 or m2 (Figs.2D, 3D) and it is badly damaged, with the entire lingual and postero-labial portion lost.The hypoflexid is wide and V-shaped, and is very close to the metafossettid.The preserved anterior margin of the metalophulid I is straight, while the posterior wall of the tooth appears to be oblique, typical of B. leanzai lower teeth.There is only a small vestige of the anterofossettid, almost lost due to wear.The preserved labial portion of the mesofossettid and metafossettid are rounded.The protoconid and hypoconid area are acute and mesio-distally aligned.
The MPEF-PV 10966e is a right m3 with moderate wear (Figs.2E, 3E).It is assigned to a m3 due to the short posterior lophid and lack of wear facet on the posterior wall.Metalophulid I and II are connected at the lingual extreme, defining a small and boomerang-shaped anterofossettid.This fossettid is the first one formed, and it would be rapidly lost with more wear.The hypolophid is wide and straight, and is as long as the metalophulids.The posterolophid is the shortest lophid with an antero-posteriorly oblique orientation, so the trigonid is much longer than the talonid.The area of the protoconid is more la-bial than the hypoconid area.The mesoflexid is funnel shaped and large, extending beyond the middle of the occlusal surface.Its labial extreme is rounded and slightly curved anteriorly.The metaflexid also extends beyond the middle of the tooth, almost reaching the hypoflexid.It is transversal, with a rounded labial extreme and triangular outline.The mesoflexid is the last flexid to become a fossettid, but it seems that this is slightly variable between the specimens from Cerro Bandera.The hypoflexid is short and wide, with a V-shape outline and antero-posteriorly oblique.It does not pass the middle of the tooth and is markedly shorter than the lingual flexid.
Cephalomyids are poorly known, excepting Cephalomys; and thus, more collection efforts are needed in order to find more and more complete material that allow to shed light to this intriguing caviomorph family.

Table 1 .
Cephalomys; unilateral hypsodonty in the uppers.Cement absent.Unworn or little worn upper molars with pentalophodont or tetralophodont occlusal pattern; the labial flexi are wide and transverse, and the hypoflexus extends less than half way across the occlusal surface.Worn upper molars with rounded labi-Dental measurements of Banderomys leanzai from La Estrella.Abbr.: AW, anterior maximum preserved width; L, total preserved length; PW, posterior maximum preserved width.Measurements in mm.al fossettes; the mesofossette is the largest and most persistent, as in Cephalomys; hypoflexus extends only half way across the occlusal surface.Lower molars are tetralophodont during early and moderate stages of wear, lingual end of the metalophulid II connected with the posterolabial slope of the metaconid.The anterofossettid is the smallest and most ephemeral lingual flexid, and with wear the occlusal pattern turns trilophodont.
of Chubut Province.The age of La Estrella locality is supported by the sedimentological data (see Geological Setting above) and mammal assemblage, especially by the presence of Mazzonicebus almendrae, Perimys and Eosteiromys which are not found in older SALMAs.This new record enlarges the geographical distribution of B. leanzai for the Colhuehuapian SALMA.Most genera of caviomorph rodents found in Cerro Bandera are present in other pre-Deseadan to "Colloncuran" localities of Argentina, Bolivia, and Chile.