Amargasaurus, a Sauropod dinosaur from the early Cretaceous Period (around 130 million years ago). Amargasaurus was small for a Sauropod and featured two rows of spines down its neck and back. Photo taken in Victoria Museum, Melbourne, Australia.
The earliest ancestor of pterosaurs could have been something like this. This is a speculative animal. Arboreal ornithodiran with long fingers to climb, arm-bound air sacs used for social displays (they will extend into the wings later,).