The junior led the Terps in scoring last season, averaging 15.1 points per game.
Wiggins earned all-Big Ten honorable mention honors last season.
Smart played in 22 games as a freshman, tallying 30 points.
Turgeon's contract will pay $17.5 million over five years.
Russell averaged 14.7 points, 4.5 rebounds and 4.5 assists with Rhode Island this season.
Wahab fills a desperate need for the Terps in the low post.
Marial averaged 1.3 points and 1.3 rebounds while playing under six minutes per game this season.
Owusu was held scoreless in the fourth quarter in the Terps' season-ending loss to Texas.
The Terps scored their fewest points all season as they were bounced in the Sweet 16.