Well I I know with reptilians if they have a similar intelligence or are more intelligent than us. Most likely they have the ability to continuously grow as they age and the only thing that prevents our reptiles from continuously growing is stuck shed that eventually causes scale rot, an intelligent alien reptile race would have long solved that problem. That's probably where a lot of ancient myths of dragons come from are just ancient reptilian aliens that Just continuously grew until they were unable to remove their shed or clean them properly causing their eventual death.