The Roscommon-born forward's place has gone to Clontarf front rower Robert Sweeney, a member of the Leinster Development squad.
Sweeney was a member of the Ireland squad that travelled to France in 2003 for the IRB Under-19 World Cup.
Jonathan Sexton is also included in coach Mark McDermott's set of backs.
The Irish, who grabbed an excellent second place at last year's tournament, play their opening 2005 match against France in Chacras R.C. on Thursday, June 9 at 7.00pm (Irish time).
The competition - which runs from June 9 to 25 - will take place at five venues throughout Argentina's Mendoza region, namely Liceo, Chacras, Maristas, Mendoza and the M. Argentinas Stadium.
The Ireland Under-21 squad to take part in the IRB Under-21 World Cup in Argentina is as follows:
Forwards: John Andress (Belfast Harlequins), Ryan Caldwell (Dungannon), Stephen Ferris (Dungannon), Chris Henry (Malone), Anthnony Kavanagh (Garryowen), Ronan Loughney (Galwegians), Gary Maxwell (Dungannon), Kevin McLaughlin (UCD), Mark Melbourne (Garryowen), Joseph Merrigan (Corinthians), Ross Noonan (UCC), Stuart Philpott (Saracens), Trevor Richardson (Buccaneers), Robert Sweeney (Clontarf).
Backs: Conan Doyle (Garryowen), Gerry Hurley (Garryowen), Paul Hurley (UCC), Mark Kettyle (Belfast Harlequins), Ross McCarron (UCD), Paul McKenzie (Belfast Harlequins), Daniel Riordan (Corinthians), Jonathon Sexton (St Mary's College), Greg Stafford (Lansdowne), Gareth Steenson (Dungannon) (Capt), Andrew Trimble (Ballymena), Cillian Willis (UCD).
Coach: Mark McDermottAssistant Coach: Niall Malone Manager: David Haslett
IRB Under-21 World Cup: Ireland Schedule:
Thursday, June 9: Ireland U-21 v France U-21, Chacras RC, 7.00pm
Monday, June 13: Ireland U-21 v Samoa U-21, Maristas RC, 7.00pm
Friday, June 17: Ireland U-21 v South Africa U-21, Liceo RC, 7.00pm
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