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Miohippus assiniboiensis
Taxonomy
Mesohippus assiniboiensis was named by Lambe (1905). Its type specimen is Ottawa Mus. 6305, a tooth (second right upper premolar, p2, unworn), and it is a 3D body fossil.
It was considered a nomen dubium by Macdonald (1992); it was recombined as Miohippus assiniboiensis by Prothero and Shubin (1989), Storer and Bryant (1993) and MacFadden (1998).
It was considered a nomen dubium by Macdonald (1992); it was recombined as Miohippus assiniboiensis by Prothero and Shubin (1989), Storer and Bryant (1993) and MacFadden (1998).
Synonyms
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Synonymy list
| Year | Name and author |
|---|---|
| 1905 | Mesohippus planidens Lambe p. 49 figs. Pl. 2:7 |
| 1905 | Mesohippus assiniboiensis Lambe p. 50 figs. Pl. 2:8 |
| 1908 | Mesohippus assiniboiensis Lambe |
| 1908 | Mesohippus planidens Lambe |
| 1918 | Mesohippus assiniboiensis Osborn p. 44 figs. Text Fig. 24(22,23,24) |
| 1918 | Mesohippus planidens Osborn p. 44 figs. Text Fig. 24{21) |
| 1940 | Mesohippus assiniboiensis Stirton p. 170 |
| 1940 | Mesohippus planidens Stirton p. 170 |
| 1989 | Miohippus assiniboiensis Prothero and Shubin |
| 1993 | Miohippus assiniboiensis Storer and Bryant |
| 1998 | Miohippus assiniboiensis MacFadden p. 544 |
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If no rank is listed, the taxon is considered an unranked clade in modern classifications. Ranks may be repeated or presented in the wrong order because authors working on different parts of the classification may disagree about how to rank taxa.
†Miohippus assiniboiensis Lambe 1905
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Invalid names: Mesohippus planidens Lambe 1905 [synonym]
Diagnosis
| Reference | Diagnosis | |
|---|---|---|
| H. F. Osborn 1918 | (Lambe, 1905). (1) The type of larger size than that of Miohippus intermedius or M. validus from the Protoceras zone. (2) development of parastyle than in M. brachystylus; (3) proto- and metalophs short, set at right angles to ectoloph; (4) deutero- and tetartocones of premolars strongly and equally developed; (5) protoconule
much smaller than metaconule; (6) ectoloph with .distinct mesostyle; (7) hypostyle tends to separate from posterior cingulum; (8) cingulum robust, high and sharp. Lambe observes (op. cit. p. 50) that this animal, known only from the second upper premolar, approaches most nearly in tooth development the much smaller Miohippua brachyatylus Osborn.It most closely resembles Miohippus validus in size, but is considered even larger. | |
| H. F. Osborn 1918 (Mesohippus planidens) | (Lambe, 1905, p. 49) "These teeth indicate a species of about the size of M. intermedius, Osborn and Wortman, from the Upper Oligocene, Protoceras beds of South Dakota, but smaller than M. validus, Osborn, from the same horizon and state. They differ from those of M. intermedius in the greater obliquity of the protoloph and metaloph in which respect they resemble those of M. obliquidens, Osborn. The teeth are brachyodont, and are devoid of an internal cingulum. Externally the ectoloph is noticeably flat with only a slight development of the parastyle and mesostyle, the ribs are absent or but feebly indicated, and the metastyle is particularly inconspicuous. The hypostyle is of fair size, curved and attached at either end to the posterior cingulum. The cross crests are oblique to the ectoloph, well elevated, and moderately continuous, the metaloph more so than the protoloph. The protoconule slightly interrupts the protoloph and unites with the parastyle. The metaconule scarcely breaks the continuity of the metaloph which is sharply separated from the ectoloph and develops a rudimentary crochet. The protocone and hypocone are not so elevated as the ectoloph. The specific name has reference to the flattened condition of the ectoloph." |
Measurements
No measurements are available
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| Source: f = family, subc = subclass, c = class, subp = subphylum | |||||
| References: Nowak 1991, Hendy et al. 2009, Carroll 1988, Lillegraven 1979, Ji et al. 2002 | |||||
Age range: base of the Whitneyan to the top of the Monroecreekian or 33.30000 to 24.80000 Ma
Collections: one only
| Time interval | Ma | Country or state | Original ID and collection number |
|---|---|---|---|
| Whitneyan - Monroecreekian | Canada (Saskatchewan) | Miohippus assiniboiensis (17306) |