Desmatippus, SCOTT, 1893

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 : 24

DESMATIPPUS SCOTT, 1893

Desmatippus avus MARSH, 1874

Holotype —From UCMP V65400 : right p3 through m2, left p2, p3, p4 and m1, left P2 through M1, M3, and right P2, M2, a canine and fragments, YPM 11281 .

Referred specimens — From JDNM-4: three upper molars (former type of Parahippus brevidens Marsh, 1874 ), YPM 11274 . From JDNM-4*: right upper molar or premolar, JODA 1983 ; right M3, JODA 1992 ; right upper molar, JODA 2050 ; right and left P1 through M3, JODA 2435 ; upper molar, JODA 2428 . From UCMP V4830-4835 : left upper molar, UCMP 1701 . From UCMP V4834 : upper partial left premolar or molar, UCMP 40240 . From CIT 113: upper molars or premolars, CIT 406 and CIT 407.

Occurrence — UCMP V 65400, JDNM-4, JDNM-4*, UCMP V 4830-4835, UCMP V 4834, CIT 113, JDNM-4.

Description —All YPM and CIT material are described in Downs (1956). JODA specimens are new occurrences. JODA 1983 is a well-worn, low-crowned cheek tooth. It does not contain a crochet; however, there is cement present. It measures ap= 17.42 mm and t= 19.72 mm. JODA 1992 is also a well-worn, low-crowned specimen with no crochet (ap=16.87, t= 18.65 mm). JODA 2050 has the following measurements: ap=17.25, t= 15.29 mm. None of the molars nor premolars of JODA 2435 contain a crochet, and all are low-crowned and have minimal cement. They are similar in size and wear stage as YPM 11281. JODA 2428 also lacks a crochet, is low-crowned and has no cement. Placement of these specimens in this taxon is based on the absence of crochet and no connection between the protoloph and protocone on upper cheek teeth, minimal cement in cheek teeth and brachydont dentition.

Remarks — MacFadden (1998) placed less-derived parahippines into Desmatippus . This includes subsuming Parahippus avus Marsh, 1874 into Desmatippus based on low-crowned molars, lack of a crochet and lack of cement. There are variable amounts of cement on the JODA referred specimens, ranging from no cement to minimal cement; however, all lack a crochet. Downs (1956) had previously synonymized P. brevidens and P. avus . YPM 11281 was originally reported by Downs (1956) as YMP 1128. Less-derived parahippine specimens that are low-crowned, lack a crochet and have minimal or no cement from the type area of the Mascall are placed within this species while more derived parahippine specimens are placed in Parahippus sp. (see below).