News Finding: According to the team, this demonstrates that the first and fifth digits were not simply lost to evolution, but attached to their neighboring second and fourth digits.
Paper Finding: Our proposed locations of the proximal metacarpals are confirmed by their carpal articulations, which are consistent with those of the pentadactyl Phenacodus.
News Context: Fragments of the 'missing' digits can be found in the form of ridges on the backside of the splints." According to the team, this demonstrates that the first and fifth digits were not simply lost to evolution, but attached to their neighboring second and fourth digits. "With a distinct surface from the metacarpal, we know the splints on today's horses to be the remnants of the second and fourth digits," Professor Solounias said.
Paper Context: The splint metacarpals, previously interpreted as reduced digits II and IV, also contain remnants of digits I and V compressed as ridges onto the ventral surface. Our proposed locations of the proximal metacarpals are confirmed by their carpal articulations, which are consistent with those of the pentadactyl Phenacodus. The tridactyl equid Mesohippus shares the ventral ridges on the side digit bones, many of which appear to have a distinct fusion line, and exhibits a lesser degree of digit reduction than previously thought.