Balantiomys, KORTH, 1997

Maguire, Kaitlin Clare & Schmitz, Joshua X. Samuels and Mark D., 2018, The fauna and chronostratigraphy of the middle Miocene Mascall type area, John Day Basin, Oregon, USA, PaleoBios 35, pp. 1-51 : 18

BALANTIOMYS KORTH, 1997

Balantiomys oregonensis GAZIN, 1932

FIG. 9

Referred specimens —From CIT 1869: left dentary with p4 through m3, CIT 4001; isolated P4, M1, M2 and M3, CIT 3999. From UCMP -3043: left dentary with dp4 and partial m1, JODA 3767. From UCMP V 4823: upper right M3, JODA 15648.

Occurrence —CIT 1869*, UCMP -3043, UCMP V 4823.

Description —CIT 4001 is tentatively placed in this genus on the following characteristics of the p4: metalophid cusps large and subequal in size, no anterioposterior valley between the metaconid and protostylid, anterostylid on anterior slope of protostylid. CIT 3999 is also tentatively placed in this genus, following Downs (1956). JODA 3767 is the first occurrence of a dp4 for the species ( Fig. 9 ). The posterior cingulum is broad anteroposteriorly, connecting centrally to the hypoconid and entoconid. The hypoconid and entoconid are equal in size. The central enamel ridge connects to the protosylid. The protoconid/metaconid complex is crescent shaped.

Remarks — Korth (1997) has B. oregonensis as the only species belonging to the genus outside of the Great Plains. Full descriptions and a thorough discussion of CIT 3999 and 4001 are in Downs (1956). Overall, the specimens are fragmentary and well-worn, therefore, making identification difficult. Both specimens are from the Bode collection of 1929 and assigned to CIT location 1869. CIT 4001 is labeled from “West of Dayville Highway” and was purchased by the Weatherfords. CIT 3999 is labeled from “North of Dayville”. Downs (1956) identified UCMP 442, a partial skull with P4 through M3, as Peridiomys cf. oregonensis Gazin, 1932 and claims it is from the Mascall based on this identification even though it was originally assigned to the Hemingfordian of the John Day Formation. It is not an entoptychine based on the protoloph shape of the P4, however, the amount of wear makes it impossible to assign this specimen to B. oregonensis rather than to another primitive heteromyid. An additional specimen from CIT 1869, CIT 4000, is a dentary with heavily-worn p4‒m2 making identification beyond Heteromyidae difficult; however, it does fall within the size range of B. oregonensis .

Figures

Figure 9. Balantiomys oregonensis right dp4 in occlusal view, JODA 3767. Scale bar=1mm.