Here’s my take:
Low IQ: crosc looks like dinos so they are the cloests living relative to dinos. Mid IQ: birds are direct descendents of dinos so they are the closest living relatives to dinos. High IQ: since birds are direct descendent they are just dinos, not a relative. Which makes crocs the next closest living relative to dinos/birds.
Beat the game with my SO. Lovely time.