Parahippus, LEIDY, 1858

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 : 25

PARAHIPPUS LEIDY, 1858

Parahippus sp.

Referred specimens —From JDNM-4*: left P2, JODA 2401; left P3, JODA 2402; left P4 or M1, JODA 2403; left M2 or M3, JODA 2404; left P4, JODA 2405; left P4, JODA 2406; right M1, JODA 2407; right P2, JODA 2408; right P4, JODA 2409; right M3, JODA 2411; left M3, JODA 2412; left p2, JODA 2413; lower left molar or premolar, JODA 2415, lower right molar or premolar, JODA 2417; right M1 through M3?. From UCMP V 4941: upper right molar, UCMP 40314.

Occurrence —JDNM-4*, UCMP V 4941.

Description —The protoloph does not connect to the protocone on upper cheek teeth. Some have complex crenulation patterns and/or crochets, while others lack them. The majority of specimens have at least some cement; in some cases the amount of cement is considerable (pre- and postfossettes are filled and protocone is surrounded), especially in teeth that are unworn or slightly worn. All specimens are low-crowned with heights ranging from 9.25‒16.4 mm and an average of 12.5 mm. These characteristics place these specimens within parahippines and align them more closely to Parahippus than Desmatippus .

Remarks — Downs (1956) reported a small deciduous tooth (UCMP 31987) from UCMP -3059 as P. sp., however, this specimen is a lower molar or premolar and belongs to Archaeohippus ultimus . The genus Parahippus contains a heterogeneous assemblage representing a morphocline from low-crowned, less-derived molars to higher-crowned, more complex molars ( MacFadden 1998). The specimens assigned to this genus from the type area of the Mascall Formation are distinguished from Desmatippus in being on the more derived end of the morphocline with the presence of crochets, cement and incipient hypsodonty. Hunt and Stepleton (2004) note the occurrence of Parahippus pawniensis Gidley, 1907 from the Hemingfordian age Rose Creek Member strata south of Kimberly, Oregon. Parahippus is also recorded from the Late Arikareean‒Early Hemingfordian Warm Springs locality in central Oregon ( MacFadden 1998).

cf. Parahippus sp.

There are several equid premolars and molars in the JODA collection that are similar to Desmatippus avus , except they contain a fair amount of cement and some have a crochet. Therefore, they most likely fall further along on the morphocline between Desmatippus and

Parahippus ( Stirton 1940, MacFadden 1998). Here they are placed within cf. Parahippus , but a taxonomic revision of both genera may shed more light on the identification of these specimens.