Fig. 30 in Phyletic Diversification Of The Cormohipparion Occidentale Complex (Mammalia; Perissodactyla, Equidae), Late Miocene, North America, And The Origin Of The Old World Hippotherium Datum

Fig. 30. Cladogram of species of Cormohipparion, the LACM specimen, and Hippotherium primigeniuim with outgroups of Parahippus leonensis, ''Merychippus'' primus, M. insignis. Tree length is 124; Consistency Index is 0.742; Retention Index is 0.782; Homoplasy Index is 0.258. Bootstrap values are in boldface. Based on a character distribution analysis via MacClade 4.08. Nodes 1–8 are as in fig. 27. At Node 9, the maxillo-lacrimal and naso-lacrimal sutures form an obtuse angle (14:0); the posterior border of the premolar prefossette has 8–9 plis (23:4). C. matthewi is distinguished by having a reduced MSTHT to ca. 42 mm (18:3), and a lower premolar ectoflexid that penetrates the space between the metaconid and metastylid (31:0). At Node 10, the molar posterior prefossette increases to 10 or more (24:5); the premolar postfossette plis increase to 2–3 (27:1); the molar postfossette plis similarly increase to 2–3 (28:1); and the molar pli caballin is usually double (30:2) The LACM specimen of Cormohipparion is distinguished by having reverted to a P2 protocone that attaches to the protoloph within 20–30% wear (20:2); an increase in premolar posterior prefossette plis to 10 or more (23:5); and an increase in premolar plis caballin to 4 (29:4). Node 11 has no distinguishing characteristics but is the point at which C. occidentale and H. primigenium diverge from the LACM specimen of Cormohipparion. H. primigenium is distinguished by the IOF located above the P2–P3 boundary (10:0); the low position of the IOF relative to the ventral border of the orbit (11:0); the maxillo-lacrimal and naso-lacrimal sutures forming an acute angle (14:1); the maxillo-lacrimal and lacrimo-jugal sutures forming an acute angle; the dP1/P2 length ratio retained at ca. 60% (17:1); and their being 8–9 molar anterior postfossette plis. C. occidentale is distinguished in having an unworn cheek tooth MSTHT 60–66 mm (18:6); their being 8–9 molar posterior prefossette plis (24:4); and the orbit being posterior to M3 (38:2). At Node 12, the IOF is located above P2 (36:1). C. fricki is distinguished by having a palpable anterior rim of the DPOF (8:1); molars have 2–3 plis on the anterior border of the prefossette (22:1); the protocone retains a spur (35:0); and the orbit is posterior to M3 (38:2). C. skinneri is distinguished by having the lower premolar ectoflexid making an X-pattern with the metaconid/metastylid (31:2).