The Dolphins also signed free-agent receiver Ernest Wilford to a four-year contract. He had a career-high 45 catches for 518 yards and three touchdowns last year with Jacksonville.
Ryan signed a one-year deal. The 6-5, 265-pound tight end spent the past two years with the New York Jets and has career totals of nine receptions for 90 yards.
The trade for Ferguson, 33, involved undisclosed draft choices. He has started 106 games, beginning his career with the Jets before joining Dallas in 2005.
Copyright 2008 by The Associated Press.