These monsters are called Salamanders. They are unique in that they have no Guardian coloration and yet can still be found all over islands including in positions where they are guarding chests.
Throdamas and Symurghs are not native to Europa. They are from Ganymede and Io respectively and as such can only be obtained in the wild through The Portal on the Battlefield. Information on these two species can be found in the Beast Codex.
Lykos, on the other hand, are from Europa but were only able to be found in their Hibernating Egg state on the winter-exclusive Tundra biotype. A Liquid Deviance, extracted from deviant pets, is needed to activate the eggs and the eggs could then be upgraded with Liquid Vermillion from the Battlefield for a better chance at getting better genes.
As SiberianWhite said these pets are also available in the pound and pet auctions, and you can also check the Pet Sales here in the forums to look for people who are selling these species of beasts.