Didelphis, Linnaeus, 1758

Stutz, Narla S., Hadler, Patricia, Negri, Francisco R., Marivaux, Laurent, Antoine, Pierre-Olivier, Pujos, François, Jacó, Tiago R., Fontoura, Emmanuelle M., Kerber, Leonardo, Hsiou, Annie S., Santos, Roberto Ventura, Alvim, André M. V. & Ribeiro, Ana Maria, 2023, New records of marsupials from the Miocene of Western Amazonia, Acre, Brazil, Acta Palaeontologica Polonica 68 (3), pp. 457-475 : 464

Didelphis cf. Didelphis solimoensis Cozzuol, Goin , de los Reyes, and Ranzi, 2006

Fig. 6C.

Material.— UFAC-CS 415, left DP3 from the locality PRE 06 , sampling point C, Envira River , State of Acre, Brazil; Solimões Formation , Acre Basin, (?lower) Upper Miocene .

Measurements.—L = 3.08 mm; W = 3.22 mm.

Description.—This DP3 is anteroposteriorly elongate in its labial portion and relatively narrow. The protocone is slightly anterior to the paracone, forming a small, triangular-shaped trigon basin, which is deep and anteroposteriorly compressed. The metacone is conic and posteriorly oriented. It is high and well developed. At its dorsolingual base, there is a small metaconule. The centrocrista is well developed and U-shaped. The preparacrista is almost vertical and does not reach the anterior cingulum/StA. There is a very long postmetacrista, which is obliquely oriented towards the StE. The pre- and postprotocrista are well developed, short, and oblique. There is a well-developed anterior cingulum passing along the base of the paracone and joining a small paraconule. At its labial extremity, there is a small StA. A well-marked labial cingulum is present, extending from StA up to StC. The StB is high and fused with the paracone. Next to StB there is a small and rounded StC, which is closer to StD. The StD is wide and slightly shorter than StB, it is located labial to the metacone and followed by a marked crest, which is oriented parallel to the anteroposterior dental axis. At its end, a small StE forms a rounded posteriormost tip.

Remarks.—Based on its morphological characteristics and dimensions, UFAC-CS 415 belongs to a didelphid smaller than species of Didelphis , Lutreolina , Philander , and Chironectes but larger than Marmosa murina (Linnaeus, 1758) . Compared with UFAC-CS 413, UFAC-CS 415 is morphologically different from it, and it resembles the DP3 morphology of Didelphis , such as the development and position of the cusps, trigon basin, and stylar cusps, and well-developed anterior cingulum and by being anteroposteriorly elongate. However, UFAC-CS 415 has smaller dimensions than what it is observed in the living species of Didelphis . Didelphis solimoensis , from the Upper Miocene of Acre, is considered the smallest known species of the genus ( Cozzuol et al. 2006). UFAC-CS 415 might be slightly smaller than D. solimoensis . However, it should be noted that D. solimoensis is only known from an isolated dentary with p3–m2. Still, given that the occlusal morphology of UFAC-CS 415 resembles the one of Didelphis DP 3s and that D. solimoensis is the smallest Didelphis species described in the literature, UFAC-CS 415 was assigned to Didelphis cf. D. solimoensis , pending the discovery of additional specimens of the former, especially preserving the upper dentition.