I haven't read all of the replies to this thread, but I just wanted to let you know that I have a 20m DS who never crawled. Once he started rolling he didn't do anything else until just after 12m when he started bum shuffling. He has always been a fantastic talker and started speaking and saying lots more words than some of his other friends much earlier than them, had a good 50 + words at 18m. I have never worried about the fact that he hasn't crawled and it hasn't seemed to interrupt his development at all. I hope this helps a little.