Dog

A Dog (Canis lupus familiaris) is a mammalian animal native to Earth. A subspecies of the wolf, the dog was one of the first animals to be domesticated by humans - as recently as 15,000 years ago. There were a wide variety of breeds of dogs, with different sizes, temperaments, and type of coats. Dogs were often kept as pets by humans, and were also used for a variety of other tasks by humans.

Jonathan Archer had a male beagle named Porthos that he took with him on board the Enterprise (NX-01). Porthos stayed with Archer for his entire time as Captain of the Enterprise. (ENT episode Broken Bow, et al)

As a child, Miles O'Brien had a dog. (DS9 episode The Forsaken).

The USS Enterprise (NCC-1701-D) once carried a litter of puppies that Deanna Troi brought her child Ian to play with. (TNG episode The Child).

Lieutenant Aquiel Uhnari kept a large dog which she had named Maura. Maura was killed in 2369 by a coalescent organism, which had subsequently assumed the dog's form. (TNG episode Aquiel).