Class Mammalia
Order Perissodactyla
Family Equidae
Equus calobatus—Stilt-legged Onager // Equus francisci—Stilt-legged Onager
The position of this taxon in relation to E. francisci is unclear. Kurtén and Anderson (1980) cite E. calobatus as the largest of the stilt-legged horses (subgenus Hemionus), whereas E. francisci (E. tau of Kurtén and Anderson) is said to be the smallest of the North American Pleistocene horses (Dalquest 1979). Winans (1985) considered E. calobatus to be a junior synonym of E. francisci. Vanderhill (1986), in considering Blancan to Irvingtonian specimens from fossil beds revealed by the incision of the Rio Grande Valley, referred material to this taxon, retaining E. calobatus as valid.
Sites.
Late Blancan: 111 Ranch (Morgan and White 2005: ?); La Union (Morgan and Lucas 2003: ?); Santo Domingo (Morgan and Lucas 2003: ?).
Early Irvingtonian: Adobe Ranch (Morgan and Lucas 2003: cf.).
Irvingtonian: El Paso (UTEP).
Literature.
Dalquest 1979; Kurtén and Anderson 1980; Morgan and Lucas 2003; Morgan and White 2005; Vanderhill 1986; Winans 1985.
Synonyms. Equus tau.
Dalquest (1979) considered Equus francisci to be a synonym of Equus tau, and E. tau to be the only small, stilt-legged horse of the Pleistocene. He characterized it as the smallest of the North American Pleistocene horses.
Winan (1985, 1989) considered this a valid species (or species group) of stilt-legged horse. In these, the length to proximal width of the metacarpal is generally greater than 5.0 and that of the metatarsal, greater than 6.0 (Winans 1989).
Occurrence in the Balcony Room site of Dry Cave is based solely on a single, partial
upper tooth (Figs. 1 and 2) that is appreciably smaller than that of E.
conversidens.
Fig. 1. Occlusal views of an upper cheek tooth of E. conversidens (left) and that of E. francisci (right). Scale is in mm.
Fig. 2. Longitudinal lateral and internal views of the specimen identified as E. francisci. Scale in mm.
Sites.
Rancholabrean: Papago Springs Cave (Skinner 1942); .
Late Wisconsin: Balcony Room (Harris 1993c); Bonfire Shelter (Bement 1986); Burnet Cave (Schultz and Howard 1935: cf.); Cueva Quebrada (Lundelius 1984); White Mesa (Morgan and Rinehart 2007: cf.).
Literature.
Bement 1986; Dalquest 1979; Harris 1993c; Lundelius 1984; Morgan and Rinehart 2007; Schultz and Howard 1935; Skinner 1942; Winan 1985, 1989.
Last Update: 15 Mar 2013