Experienced fullback Rob Kearney has been omitted from Andy Farrell's first Ireland squad since taking over as coach.
Farrell named a 45-man squad overnight for a mid-season camp, the first official step towards the 2020 Six Nations.
The former England assistant took over from Joe Schmidt after Ireland's World Cup quarter-final exit and there will be plenty of focus on the Irish as 2020 rolls around.
This squad could be telling one for Australians too, with Ireland set to play the Wallabies three times in 2020 - twice in Australia in next year's July series and once in Dublin in November.
Star flyhalf Johnny Sexton has been named in the group despite being in potential doubt for Ireland's Six Nations opener in February 2020.
The news isn't so good for Tadhg Beirne, who is set for ankle surgery that will put him in doubt for Europe's main rugby tournament.
Farrell said he hoped this short gathering would help build bonds in the group for next year.
"The national coaches have been around the provinces watching games and having good conversations with players and the provincial coaches," said Farrell.
"We have limited opportunities across the busy provincial season to bring a broad group like this together but this 24-hour window will allow us to plant a few seeds.
"It will also give the coaches a better insight into a few players who been performing consistently well for their provinces.
"The next six weeks is the window for players to put their hands up for selection for our first squad which will be named in late January ahead of the Six Nations."
Ireland extended squad
Connacht: Bundee Aki, Caolin Blade, Ultan Dillane, Dave Heffernan, Quinn Roux
Leinster: Ross Byrne, Will Connors, Max Deegan, Caelan Doris, Tadhg Furlong, Jamison Gibson-Park, Cian Healy, Robbie Henshaw, Dave Kearney, Ronan Kelleher, Jordan Larmour, Luke McGrath, Andrew Porter, Garry Ringrose, Rhys Ruddock, James Ryan, Jonathan Sexton, Devin Toner, Josh van der Flier
Munster: Joey Carbery, Andrew Conway, Keith Earls, Chris Farrell, Mike Haley, Dave Kilcoyne, Jean Kleyn, Conor Murray, Peter O'Mahony, Niall Scannell, Rory Scannell, CJ Stander
Ulster: Will Addison, Billy Burns, John Cooney, Iain Henderson, Rob Herring, Stuart McCloskey, Marty Moore, Tom O'Toole, Jacob Stockdale