Another thought is that the creatures who crew UFOs might not be from another planet, but might have been genetically built and incubated right here on earth in one of those secret underground laboratories, and not by aliens, but by human tinkerers. Suppose the saurian is not a creature who lived before us, but is the creature, by genetic manipulation, some of us are soon to become. Some reptiles, remember, have an uncanny ability to regenerate lost parts, often two or three parts. This would prove a real benefit for explorers on a planet several million miles from home base where spare arms and legs are not readily available. Some reptiles appear to be unaffected by cosmic radiation that is killing human beings by the thousands.
Some reptiles can hibernate for months and years at a time without suffering adverse effects.
Cruel experiments on humans in Germany during the second war helped put American and Russian Cosmonauts into space only two decades later. Those experiments haven't stopped simply because we have no announced plans to return to the lunar surface soon. In turn, the vertical posture removed the need for a tail. The legs were modified by lowering the ankle to the ground and the foot was lengthened. It would have stood upright at about five feet tall.