We revisit digit reduction in the horse and propose that all five digits are partially present in the modern adult forelimb. Osteological descriptions of selected tetradactyl, tridactyl and monodactyl equids demonstrate the evolution of the forelimb. Histological, osteological and palaeontological evidence suggest that the Equus distal forelimb is more complex than traditionally conceived. The current understanding is that the horse distal forelimb consists of one complete digit (III) and two reduced splint metacarpals (II and IV). Metacarpals II and IV each exhibit a ventral ridge, which we suggest represents the undifferentiated digits I and V. These ridges are present in the tridactyl Mesohippus, but are absent in the tetradactyl Hyracotherium. The carpal articulations of the five metacarpals match those of pentadactyl taxa. Distally, the frog, a V-shaped structure on the ventral hoof represents digits II and IV, and the wings and hoof cartilages of the distal phalanx are digits I and V. We relate this revised interpretation of the Equus forelimb to Laetoli footprints, and suggest the Hipparion side impressions are created from the hooves of I and V, rather than from II and IV. We show shades of pentadactyly within the Equus manus.

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Several evolutionary theories have been proposed to explain the adaptation of the long giraffe neck; however, few studies examine the fossil cervical vertebrae. We incorporate extinct giraffids, and the okapi and giraffe cervical vertebral specimens in a comprehensive analysis of the anatomy and elongation of the neck. We establish and evaluate 20 character states that relate to general, cranial and caudal vertebral lengthening, and calculate a length-to-width ratio to measure the relative slenderness of the vertebrae. Our sample includes cervical vertebrae (n=71) of 11 taxa representing all seven subfamilies. We also perform a computational comparison of the C3 of Samotherium and Giraffa camelopardalis, which demonstrates that cervical elongation occurs disproportionately along the cranial–caudal vertebral axis. Using the morphological characters and calculated ratios, we propose stages in cervical lengthening, which are supported by the mathematical transformations using fossil and extant specimens. We find that cervical elongation is anisometric and unexpectedly precedes Giraffidae. Within the family, cranial vertebral elongation is the first lengthening stage observed followed by caudal vertebral elongation, which accounts for the extremely long neck of the giraffe.