Dromomeryx, DOUGLASS, 1909

Maguire, Kaitlin Clare & Schmitz, Joshua X. Samuels and Mark D., 2022, The fauna and chronostratigraphy of the middle Miocene Mascall type area, John Day Basin, Oregon, USA, PaleoBios 35, pp. 1-51 : 31-32

DROMOMERYX DOUGLASS, 1909

Dromomeryx borealis COPE, 1878

Referred specimens —From UCMP -3059: partial skull with complete horns and post cranial elements, UCMP 1486; P4, UCMP 29985. From V 4835: left partial dentary with p2 through m2 and parts of three lumbar vertebrae, UCMP 39185; P4, UCMP 39301. From V 4831: m1, UCMP 39293. From V 4832: partial calcaneum and distal tibia, UCMP 39305. From JDNM-4*: right m3, JODA 2262. From CIT 184: horn with partial cranium and orbit, CIT 799. From Cottonwood Creek:right P3 and M3, USNM 5515; left P2 through M3, right P3 through M3, left p3 through m1, m3 and postcranial material, USNM 5516; i1 through i3, canine, partial dentary with right p2 through m3 and postcranial material, USNM 5517.

Occurrence — UCMP -3059, V 4835, V 4831, V 4832, JDNM-4*, CIT 184, Cottonwood Creek.

Remarks —All specimens are described in Downs (1956). Downs (1956) also lists several specimens assigned to this taxon that have uncertain provenance, but states they are most likely from the Mascall.

32 PALEOBIOS, VOL. 35, JANUARY 15, 2018

RAKOMERYX FRICK, 1937

Rakomeryx sinclairi MATTHEW, 1918 FIG. 18 , A, B

Referred specimens —From UCMP V4831: left p3, p4, and m1 or m2, and right p4, JODA 7195; right p3; JODA 3682. From JDNM-4*: left p4 through m3, JODA 2362.

Specimen ap (mm) t (mm) JODA 7195 p3 12.93 6.28

p4 16.73, 16.49 8.7, 8.55

m1/m2 18.99 11.5

JODA 2362 p4 15.26 8.79

m1 17.17 12.35

m2 19.68 12.72

m3 27.64 12.97

m1–m3 63.79 --

JODA 3682 p3 12.94 6.53

Occurrence — UCMP V4831 , JDNM-4 *.

Description —Specimen measurements are included in Table 6. Anterior fossette on the p4 of JODA 7195 is not closed by the anterior extension of the metaconid. The anterior fossette on the p4 of JODA 2362 is closed by the anterior extension of the metaconid, but not more so than AMNH FM 31782, which Frick identified as R. raki ( Frick 1937) . Prothero and Liter (2008) and Janis and Manning (1998) mentioned that the p4 may lack closure of the anterior fossette for this taxon. JODA 3682 is the same size and has the same preservation as the p3 of JODA 7195 and because they were collected in the same area, they probably belong to the same individual. These specimens are assigned to this taxon based on reduced premolars compared to Dromomeryx ( Table 6) and morphology of the p4 ( Janis and Manning 1998)

Remarks —Prothero (2008) places all species of the genus into R. sinclairi . There is another specimen at LACM (with no specimen number) that may be attributed to this species; however, additional preparation is needed for identification. JODA 7195 and 2362 further confirm the presence of Rakomeryx in the early Barstovian, as argued in Janis and Manning (1998).

Figures

Figure 18. Rakomeryx sinclairi. A. Left and right p4, JODA 7195. B. Left p4-m3, JODA 2362. Scale bars=1cm.