If a character has 犭 on the left, it is almost certainly an animal — and usually a four-legged mammal, not just dogs. The pedagogical name fǎnquǎnpáng ('reversed-dog side') just describes the shape; semantically it covers the full beast family. Never written alone; the standalone form is 犬.
history
犭 is the calligraphic compression of 犬, originally a pictograph of a standing dog with raised tail. In side-position the dog narrows to a curved three-stroke column: the top hook suggests the lifted head, and the diagonal slash echoes back and tail.
