Hyracodon was a lightly built,
pony-like mammal about 1.5 m (5 ft) in length, with a large
skull in comparison to the rest of the body.
Hyracodon was much smaller than modern
rhinocerotoides and differed very little in appearance from the primitive horses with which it was contemporaneous (32–26 million years ago). It had a short, broad snout and its long, slender limbs had three digits. When put next to the comtemporary
Mesohippus,
Hyracodon had a proportionally long neck, with robust vertebrae. Compared to earlier hyracodontids from the
Uinta Formation, like
Triplopus,
Hyracodon had a more gracile manus structure. The median toe was enlarged whilst the lateral toes were greatly reduced. The molars of
Hyracodon were similar to those of the modern day
Rhinoceros, with the last upper molar assuming a triangular shape. The canines and incisors, however were quite different. In form, the anterior teeth of
Hyracodon were small and similar in shape, being pointed and curved.. Like the primitive horses,
hyracodonts inhabited open forests and wooded steppes and turned from browsing foliage to grazing grass. They died out without leaving any descendants and they mark the end of the
phylogenetic branch of hornless, running rhinocerotoids. == Palaeoecology ==