Cian Healy will miss Ireland's World Cup campaign because a calf injury while Stuart McCloskey has been named in Andy Farrell's 33-man squad.
Prop Healy was injured in Ireland's final warm-up win over Samoa on Saturday and coach Farrell said his recovery could take up to 10 weeks.
Healy's absence means Munster prop Jeremy Loughman is named in the squad.
With the squad containing 15 backs, Farrell has found room for Ulster centre McCloskey.
McCloskey had started in eight of Ireland's last 12 games but there was speculation his place could be under threat because of the ability of Keith Earls and Jimmy O'Brien to play in midfield.
However, Farrell has instead opted to take four specialist centres with the Ulsterman picked along with Garry Ringrose, Robbie Henshaw and Bundee Aki.
The other players who have not made the cut from the previous 38-man squad are Ulster duo Tom Stewart and Jacob Stockdale plus Leinster back Ciaran Frawley and Connacht back row Cian Prendergast.
Ireland 33-man squad for World Cup
Forwards: Rob Herring (Ulster), Ronan Kelleher (Leinster), Dan Sheehan (Leinster), Finlay Bealham (Connacht), Tadhg Furling (Leinster), Jeremy (Loughman), Dave Kilcoyne (Munster), Tom O'Toole (Ulster), Andrew Porter (Leinster), Ryan Baird (Leinster), Tadhg Beirne (Munster), Iain Henderson (Ulster), Joe McCarthy (Leinster), James Ryan (Leinster), Jack Conan (Leinster), Caelan Doris (Leinster), Peter O'Mahony (Munster), Josh van der Flier (Leinster)
Backs: Craig Casey (Munster), Jamison Gibson-Park (Leinster), Conor Murray (Munster), Ross Byrne (Leinster), Jack Crowley (Munster), Johnny Sexton (Leinster), Bundee Aki (Connacht), Robbie Henshaw (Leinster), Stuart McCloskey (Ulster), Garry Ringrose (Leinster), Keith Earls (Munster), Mack Hansen (Connacht), Hugo Keenan (Leinster), James Lowe (Leinster), Jimmy O'Brien (Leinster).
More to follow.
World Cup Pool games
Irelandv Romania, Bordeaux, Saturday, 9 September 12:00 BST
Ireland v Tonga, Nantes, Saturday, 16 September 20:00 BST
Ireland v South Africa, Paris, Saturday, 23 September 20:00 BST
Ireland v Scotland, Nantes, Paris, Saturday, 7 October, 20:00 BST.