Umbreon is a dark-type pokemon who evolves from eevee as a result of exposure to moonlight. Like all eeveelutions, it bears a slight feline resemblance; though the only feline characteristics umbreon has is it's short muzzle and small head. Unlike Espeon, who greatly resembles a feline with its slender legs and long cat-like tail; Neither of which have retractable claws.
Umbreon resembles that of a Canine/Vulpine more than it does a Feline, with its broader legs and long bushy tail; Umbreon weighs far less than Mightyena, who is a wolf, hence Umbreon would be a smaller member of the canine family.
Glaceon is also based on a Fox (Alopex Lagopus), with the same small, feline-line head that the other 6 eeveelutions seem to share. The arctic fox is slightly smaller than others of the Vulpes family, as it is slightly smaller than Umbreon.
Umbreon: You won't know it's there until it's too late.