Potamarchus murinus Burmeister, 1885

Kerber, Leonardo, Negri, Francisco Ricardo, Ribeiro, Ana Maria, Vucetich, Maria Guiomar & Souza-Filho, Jonas Pereira De, 2016, Late Miocene potamarchine rodents from southwestern Amazonia, Brazil-with description of new taxa, Acta Palaeontologica Polonica 61 (1), pp. 191-203 : 195-196

Potamarchus murinus Burmeister, 1885

Fig. 4 , Table 3.

Material.—UFAC 1820, incomplete right dentary with m1– m3 series from Patos locality (= Acre 6 and LACM locality 4611; see Bocquentin and Melo 2006; Cozzuol 2006; Cozzuol et al. 2006; Kay and Cozzuol 2006 for details), Acre River, State of Acre, Brazil, Solimões Formation, Late Miocene.

Description.—The coronoid process is fragmented and its origin is located at the level of the posterior portion of the m3, as described in P. murinus by Burmeister (1885). On the lateral aspect of the dentary, at the level of the p4, the masseteric notch for the tendon of the medial masseter muscle is shallow. Paranamys typicus (Scalabrini in Ameghino, 1889) shows this notch at the level of the m1, and in Drytomomys aequatorialis and Dinomys branickii it is at the level of the p4–m1

→ Fig. 2. Palatal portion in the potamarchine rodent Potamarchus adamiae sp. nov. (UFAC-CS 11) from Solimões Formation, Late Miocene, Brazil, in palatal view (A) and detail of the M1–M3 series (B–D, not to scale). Sequence of tridimentional reconstructions of the palatal portion of UFAC-CS 11 (E–J).

( Candela and Nasif 2006). The preserved cheek teeth include the m1–m3 series. The m1 has four lophids and all flexids are closed. The m2 has five lophids and the last labial flexid is almost closed. The m3 has five lophids, with the last labial flexid open. The distal enamel layer of the last lophid is more convex in m1 and m2 than in m3, which is more oblique. The mesial enamel layer of each lophid is crenulated, as described by Burmeister (1885) in P. murinus and by Candela and Nasif 2006) in Paranamys cf. typicus . The size is also compatible with specimens of P. murinus from Argentina ( Table 3), differing from Potamarchus adamiae sp. nov.

Stratigraphic and geographic range.—Late Miocene of Argentina and Brazil (see Discussion).

Figures

Fig. 4. Right dentary and m1–m3 series of potamarchine rodent Potamarchus murinus Burmeister, 1885 (UFAC 1820) from Solimões Formation, Late Miocene, Brazil; in lateral view (A), showing detail of the labial view of the cheek teeth (A2); occlusal view (B), showing detail of the occlusal view of the cheek teeth (B2); and medial view (C).