Equus conversidens Owen, 1869

Tomas-Mosso, Azarael, Castañeda-Posadas, Carlos, Cruz, J. Alberto & Alarcón-Durán, Ivan, 2024, Pleistocene record of mammals and pollen from Mexico (Las Tazas, Valsequillo, Puebla) and their paleoenvironmental interpretation, Palaeontologia Electronica (a 15) 27 (1), pp. 1-18 : 5

Equus conversidens Owen, 1869

Referred material. Left M2 ( BUAPAL 773; Figure 3E ), right M3 ( BUAPAL 774; Figure 3F ).

Description. The measurement of left M2 and right M3 are: length (Al) = 24.6 mm, transversal width (Tw) = 23.81 mm and Al = 24.33 mm, Tw = 19.31 mm. Both molars present the enamel well, and its occlusal configuration can be observed, where the lingual edge of the protocone is moderately concave, the enamel folding on the outer edge of the fossettes is simple and deep, the caballing fold is simple, faint in upper left M2 and strongly developed in upper right M3.

Comparison and remarks. The structures observed in the fossils BUAPAL 774 and 773 as observed in E. conversidens ; (Reynoso-Rosales and Montellano-Ballesteros, 1994; Sánchez Salinas et al., 2016; Priego-Vargas et al., 2017). The values presented in this work are within the variation of E. conversidens and E. excelsus ( Table 2), this species are smaller in size than E. mexicanus but are larger than E. cedralencsis and E. francisi . However, there are qualitative differences that help to separate both species, such as the lion edge of the protocone, which is more concave in E. excelsus than in E. conversidens ; the folding of the enamel on the external edge of the pliprotoloph and plihypostyle pits are absent in E. excelsus and present in E. conversidens . The variation in size and occlusal characteristics of molars in equids has allowed the identification of at least five species associated in three groups of equids for the Mexican territory (Reynoso-Rosales and Montellano-Ballesteros, 1994; Sánchez-Salinas et al., 2016; Priego-Vargas et al., 2017).

Figures

FIGURE 3. Fossil material of pampathere and horses from Las Tazas, Valsequillo, Puebla. Pampatherium mexicanum: A, movable osteoderm (BUAPAL 768); B, movable osteoderm fragment (BUAPAL 767); C, fixed scapular shield (BUA- PAL 769); D, fixed scapular shield (BUAPAL 779). Equus conversidens: E, left M2 (BUAPAL 773); F, right M3 (BUAPAL 774). Equus sp.: G, right p3 (BUAPAL 771); H, right m2 (BUAPAL 772); I–J, left mandible (BUAPAL 780). Figures A–D in dorsal view; E–H and J in occlusal view; I in labial view.