Dixon is the second player to join the Nittany Lions through the transfer portal this month.
Chris Godwin and Miles Sanders each scored a touchdown in the penultimate week of the NFL's regular season.
The defensive end is currently projected as a first-round pick by many.
"I've been wanting to do that my whole life. I love you, mom."
Shelton is the second Penn State defensive lineman to enter the transfer portal Wednesday, joining Judge Culpepper.
Culpepper made five total tackles and a 0.5 sack this past season.