Microtragulus sp.

Babot, M. Judith & García-López, Daniel A., 2016, Redescription of the argyrolagid Microtragulus bolivianus (Metatheria, Polydolopimorphia, Bonapartheriiformes) based on new remains from Northwestern Argentina, Palaeontologia Electronica (Ottawa, Ont.) 51 (9), pp. 1-23 : 15-16

Microtragulus sp. Ameghino, 1904

Figure 8

Referred Material. JUY-P 53, isolated left M3; JUY-P 54, isolated left m2 or m3.

Range and Occurrence. San Roque (26º 14’ 32’’ S and 65º 21’ 55’’ W; 2940 m), 4.4 km SSW of Humahuaca town, Humahuaca Department , Jujuy Province, Argentina. Uquía Formation (late Pliocene-early Pleistocene; Marplatan SALMA, probably Vorohuan subage; Ortiz et al., 2012) .

Remarks. The isolated upper molar ( Figure 8.1 ) is considered herein an M3. The tooth is subquadrangular and exhibits an irregular central fossa; the mesiolabial border is marked as an angled corner. The area of the metacone is represented by a smooth elevation and the area of the protocone is slightly more differentiated (as a subtle corner) than the metaconular zone. The distribution of the enamel is irregular: it is clearly present in the labial wall of the tooth but is absent in the mesial side. The layer of cementum is clearly visible in the lingual and mesiolingual walls. The lower molar ( Figure 8.2 ) is characterized by a marked reduction of the talonid, both in length as in width. This condition is similar in Microtragulus catamarcensis although in this species the hypoconid is U-shaped while in the isolated molar it is V-shaped. As in other members of Microtragulus (e.g., M. catamarcensis and m1-2 of M. bolivianus ) the entoflexid is absent. The central fossid has the usual shape for Argyrolagidae , which is mesiodistally elongated.

We discard the inclusion of these molars in Microtragulus bolivianus based on their smaller size, the general outline of the upper molar (subcircular in M. bolivianus vs. quadrangular in JUY-P 53), the absence of a flexus between the mesiolabial corner and the metacone, and the angled hypoconid in the lower tooth. Nevertheless, the isolated nature and scarcity of this material prevent us from providing a specific designation.

Figures

FIGURE 8. Microtragulus sp., upper and lower molars in occlusal views. 1. JUY-P 53, isolated left M3. 2. JUY-P 54, isolated left m2 or m3. Scale bar equals 2 mm.