Archaeohippus mourningi, (MERRIAM, 1913) OSBORN, 1918

Stoneburg, Brittney E., Mcdonald, Andrew T., Dooley Jr., Alton C., Scott, Eric & Hohman, Charlotte J. H., 2022, New remains of middle Miocene equids from the Cajon Valley Formation, San Bernardino National Forest, San Bernardino County, California, USA, PaleoBios 38, pp. 1-10 : 2

ARCHAEOHIPPUS MOURNINGI ( MERRIAM, 1913) OSBORN, 1918 PARAHIPPUS (?) MOURNINGI MERRIAM, 1913 ARCHAEOHIPPUS MOURNINGI OSBORN, 1918

FIG. 2

Referred specimens —WSC 8801 lower left p2; WSC 8816 upper left DP4; WSC 8826 upper right M3;WSC 8911 worn upper tooth; WSC 8912 partial dentary; WSC 8913 worn upper tooth; WSC 9969 upper DP?.

Occurrence —Cajon Pass, San Bernardino National Forest, San Bernardino County, California. Exact locality data are on file at the USFS and WSC. Subdivision Tcv5, Cajon Valley Formation ( Woodburne and Golz 1972, Morton and Miller2003); middle Miocene, late Hemingfordian–middle Barstovian NALMA; Tcv5 (unit 5) spans approximately 16.5–14 Ma ( Liu 1990).

Description —Several teeth from a small brachydont horse were collected by WSC personnel from the Cajon Valley Formation, in subdivision Tcv5. These teeth, based upon their small size, lack of cement, and absence of a well-developed crochet, are best referred to the genus Archaeohippus ( Pagnac 2005) ( Fig. 2). WSC 8826, the only adult molar in the WSC sample, lacks a crochet completely and so is referred to Ar. mourningi ( Pagnac 2005) . Because of size and brachydont condition, all other referred specimens in the WSC sample are also referred to Ar. mourningi . Pagnac and Reynolds (2010) also described Ar. mourningi material from the Cajon Valley Formation, including a juvenile skull from Tcv5. Merriam (1913) originally named this species as Parahippus (?) mourningi , which was then transferred to the genus Archaeohippus by Osborn (1918).