L'évolution des Molaires, des Equidae éocènes, au Daman (Procavia) et au Cheval (Equus) Actuels

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From Hyracotherium of Europe, the oldest of the Equidae, parabunodont, with archaic molars, III (2) /II (2) (3 longitudinal rows of 2 tubercles, at the upper molars, 2longitudinal rows of 2 tubercles, at the lower ones), start off three chief phyla, every one extinct during the Tertiary era.
However, the actual Hyrax, by its jugal teeth, comes nearer to one of those phyla, the Palaeotherium's, of which, in the upper molars, the intermediate tubercles become effaced, while two transversal ridges, indicated, mark the toechodont type, as also do the. tubercles in V, at the lower molars.
The Equinae's phylum, of which the terminal genus, the horse (Equus), is still living, seems to separate, at the Miocene period, from a primitive north American off-spring.-At the upper molars, the intermediate crescent-like tubercles grow as big or bigger as the external ones, also in crescent, while the internal tubercles are diminishing.-The externalcrescent-liketuberclesofthelowermolars, asthefourmainonesoftheupper molars, grow more and more longer, in the antero-posterior sense, till Equus, still actual, where the belodont type attains its apogee.
By the molars' morphology (as, moreover, the extremities' morphology), Hyrax (Procaviidae) is revealed a relatively archaic perissodactyl, when the horse (Equidae), on the counter, is a very evoluted perissodactyl.