The pony is of the same species as the horse, Equus caballus . The genus Equus has eight species, although scientists have disagreed on precise classifications and whether the pony forms a distinct zoological type. Ponies have the same anatomy and general physiology as the horse, yet their conformation and character sets them apart. Physical attributes can differentiate a pony from a horse. In general, the typical pony has a compact body.
Ponies have a round shape and stocky build, which includes a wide chest and well-sprung ribs.
Other characteristics include a short head and neck, trim ears, and large eyes. In general, pony breeds typically have ample bone, as compared to the horse. In X rays, you can see that the cortex of the bone is denser, especially the Shetlands. They were on such sparse vegetation that they didn't get very big. They became tough by pulling carts out of coal mines.