M.R.
Nope - no worries! My first son never crawled, just humped the ground. My second son barely crawled. Both were walking by 10-11 months, so clearly the crawling didn't affect development. One of my friend's babies would crawl on one knee and drag her back leg. Looked hilarious! She crawled at 10-11 months as well.
But honestly, as a first time mom I was excited and dare I say proud that my son was an early walker...until I realized that it meant putting the entire house and lockdown and having to watch him like a hawk. He got into everything, everywhere, all the time. I secretly hoped my younger one would hold off a bit but nope...he was cruising at 8 months.