Mazzonicebus almendrae Kay, 2010

Novo, Nelson M., Tejedor, Marcelo F. & González Ruiz, Laureano R., 2018, Previously unknown fossil platyrrhines (Primates) of Patagonia from the Tournouër collection at the Muséum national d’Histoire naturelle, Paris, Geodiversitas 40 (22), pp. 529-535 : 532-533

Mazzonicebus almendrae Kay, 2010

HOLOTYPE. — MPEF-PV 6752 , partial mandible preserving the symphysis and left 11-M1.

GEOGRAPHIC AND STRATIGRAPHIC PROVENANCE. — Colhue-Huapi, West locality, Gran Barranca, Chubut Province, Argentina. The material was collected in the Lower Fossil Zone, Colhue-Huapi Member, Sarmiento Formation, dated between 20.0 and 20.2 Ma ( Ré et al. 2010).

NEW REFERRED MATERIAL. — MNHN.F.COL93a, left dP4; MNHN.F.COL93b, left M2.

GEOGRAPHIC AND STRATIGRAPHIC PROVENANCE. — The specimen label reads ( Fig. 3G ): “ Primate, col 93 // Colhué Huapi B // M.A. Tournouër, 1899-7 ”. Both specimens were found in the box with the same label. Thus, the provenance is certainly Gran Barranca in Chubut Province, Argentina. The Colhue-Huapi Member of the Sarmiento Formation is, early Miocene (Burdigalian Age) (see Simpson 1964; Madden & Scarano 2010 and references therein), approximately 20.0-20.2 Ma ( Ré et al. 2010).

DESCRIPTION

MNHN.F.COL93a ( Fig. 3F ), is a three rooted dP4 with unworn paracone, metacone placed more labially, and a welldeveloped protocone, as well as a hypocone placed on the distolingual cingulum. It has a morphological pattern similar to that known for the upper molars of Mazzonicebus almendrae . This tooth is smaller than M1-2 although larger than M3. It is similar in size and general aspect to the M2 of Soriacebus ameghinorum Fleagle, Powers, Conroy & Watters, 1987 , as in MACN-PV SC67, differing in that MNHN.F.COL93a has a more lingually expanded lingual cingulum which produces a triangular crown outline. One important difference is that the talon basin is distally expanded in MACN-PV SC67.

The upper deciduous dentition is not known for either Mazzonicebus or Soriacebus Fleagle, Powers, Conroy &Watters, 1987 and, in general, the deciduous dentition is scarcely known for any fossil primates from Patagonia. A dP4 assigned to Dolichocebus gaimanensis Kraglievich,1951 (MACN-PV CH 1011), provides a general morphological model of a deciduous tooth for the Patago - nian platyrrhines. Both these teeth have similar sub-triangular outlines due to the narrow lingual expansion of the lingual cingulum. This combination of features is usually seen in the dP4s of Carlocebus carmenensis Fleagle,1990 (e.g.MACN-PV SC113), and in the dP4 present in the juvenile cranium of Homunculus patagonicus, MPM-PV 3505 ( Perry et al. 2014). MACN-PV CH 1011 shows the strong hypometacrista connected to the postprotocrista, unlike that weakly developed,without connection to the postprotocrista,exhibited by MNHN.F.COL93a.In addition, they differ in that the prehypocrista in MNHN.F.COL93a is oriented more lingually with respect to the distolingual orientation observed in MACN-PV CH 1011.

Regarding the remaining tooth reported here, the comparisons between MNHN.F.COL93b and the upper molars assigned to Mazzonicebus almendrae indicate that the size ( Table 1) and morphology of the M2 match well with the M2s MPEF-PV 5699, MPM-PV 5342, and MPEF-PV 5347b; however, the lingual cingulum is less expanded anterolingually, and the molar has a very small hypocone. Its occlusal outline is more rounded instead of the nearly trapezoidal shape in Mazzonicebus . An unusual condition is seen in the hypocone development in MNHN.F.COL93b, which is divided in two tiny cusps separated by a sulcus. The metacone is aligned somewhat more lingually with respect to the paracone, and the postparacrista descends to join the premetacrista in a middle position. The protocone is well developed and has a preprotocrista reaching a shallow mesial fovea. The molar has a distinct hypoparacrista descending from the paracone, and a hypometacrista that reaches the postprotocrista at the intersection of the prehypocrista.

Other morphological characters of the M1 are shared with Mazzonicebus . For example, the cusps are moderately developed, with similar outline and depth of the trigon, a strong preprotocristid without a paraconule, talon distally expanded, and a mesial fovea is present.

On the other hand, MNHN.F.COL93b ( Fig. 3E ) was also compared with Soriacebus ameghinorum , especially the M1 of MACN-PV SC67, a maxillary fragment with well preserved M1-2. It is similar in size, has a strong preprotocrista, with the postprotocrista distally oriented to reach the hypocone, and a mesial fovea is present. MNHN.F.COL93b has a more rounded outline, but is also buccolingually shorter, and the talon is not so expanded distally as in MACN-PV SC67.The lingual cingulum is definitely more developed in MACN-PV SC67, with a strong anterolingual extension, and the hypocone is also more developed. These are the two most distinctive characters separating MNHN.F.COL93b and Soriacebus . In addition, MACN-PV SC67 has a more expanded labial side in M1-2.

Although Mazzonicebus and Soriacebus are closely related (see Tejedor & Novo 2017), these comparisons reinforce the idea that MNHN.F.COL93b is an M2 of Mazzonicebus and not an M1 of Soriacebus (see size differences in Table 1).

Figures

FIG. 3. — Map of central and eastern Patagonia modified from Tournouër (1922). Arrows pointing “Coli Huapí” and Río Coyle.