It's hard to get too excited by the record, however, when you look at the list of other rookies that have had huge passing debuts. The list includes Peyton Manning and Ryan Fitzpatrick, but otherwise not a single quarterback I've even heard of.
The list:
1. Cam Newton - 422 yards
2. Otto Graham - 350 yards
3. Ed Rubbert - 334 yards
4. Ryan Fitzpatrick - 310 yards
5. Mark Rypien - 303 yards
6. Peyton Manning - 302 yards
Otto Graham is a Hall of Fame QB and a 9-time All-Pro, who won multiple MVP awards and several championships.
Ed Rubbert was a member of the Redskins' "replacement" players team, and his claim to fame apparently is being the inspiration for Keanu Reeves' character in The Replacements. His NFL career was three games long.
Mark Rypien was a two-time Pro Bowler and was Super Bowl MVP and Offensive Player of the Year in 1991.
Obviously, nobody can project Newton's career based upon one game, but the list of guys isn't as obscure as you think.