News Finding: "While the horse's lineage is classically described as having evolved from four to three toes, and eventually one single toe, we show that its extinct ancestors exhibit the reduced toes both at the wrist and at the hoof," said co-author Melinda Danowitz, also from the New York Institute of Technology College of Osteopathic Medicine.
Paper Finding: Metacarpal IV articulates laterally with metacarpal V (one small facet) and proximally with the unciform (one large facet).
News Context: "Interestingly, we not only find hints of the missing digits on the modern horse, but also its ancestors, such as Hipparion and Mesohippus, two species believed to have three toes," Professor Solounias said. "While the horse's lineage is classically described as having evolved from four to three toes, and eventually one single toe, we show that its extinct ancestors exhibit the reduced toes both at the wrist and at the hoof," said co-author Melinda Danowitz, also from the New York Institute of Technology College of Osteopathic Medicine. "These findings show that today's horse is not truly monodactyl, and earlier ancestors were not in fact tridactyl or tetradactyl, that is, three-toed or four-toed."
Paper Context: Metacarpal III articulates laterally with metacarpal IV, and proximally with the magnum (one large facet) and unciform (one small facet). Metacarpal IV articulates laterally with metacarpal V (one small facet) and proximally with the unciform (one large facet). Metacarpal V articulates proximally with the unciform (one large facet).