Mobosaurs were the first sentient and dominant species on Mobius following the Xorda's destructive attack on the planet. The Mobosaurs were saurian in nature, similar to the ancient dinosaur species of Earth which had been extinct for millions of years. Just like their dinosaur counterparts, Mobosaurs also became extinct, this time during the ecological catastrophe known as the Coming of the Chaos Emeralds. Three of the Mobosaurs survived due to the magical properties of the Chaos Emeralds, and became the Ancient Walkers. (StH: #148, TMS: #3, SMM)
There is also the possibility that the Mobian Birds can be descendants of the Mobosaurs that survived the mass extinction event.