Dinosaurs

They are a species that fought the malignancy and lost and to escape they took their DNA and sent it to the farthest reaches of space in hopes of even one surviving to be able to seed new life. It worked, unfortunately an asteroid stopped their natural evolution.   Lucky that the Rosweliens were able to find one of these DNA capsules and breed them on a safe world until they were ready when they reached the space age the Rosweliens told them the secrets of their world and their various fates, there were treated as gods but they care nothing for that, and contacted the Zenith Council to introduce a potential affiliate of there's. The Rosweliens have kept their mouths shut on humans using their cousins fossils for fuel though.