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Jarvis, 26, will win his first Wales cap after being nominated by Howley to fill in for knee injury victim Adam Jones, while Turnbull steps into a back-row weakened by the absences of Ryan Jones and Dan Lydiate.
Knoyle’s inclusion is perhaps the biggest surprise with Bayonne scrum-half Mike Phillips forced to settle for a place on the bench as the Scarlets man makes his eighth appearance.
Turnbull wins his fifth cap after being picked ahead of Rob McCusker and Aaron Shingler, while centre Jamie Roberts returns after missing the summer tour of Australia after knee surgery.
Elsewhere, Scott Williams starts at outside centre in the absence of Jonathan Davies, who is ruled out with a groin injury and with world champions New Zealand coming to town in under three weeks, Howley admits there has never been a better time to impress.
“There are obvious opportunities for the likes of Aaron, Tavis at scrum-half and Josh in the back-row, to pull on the jersey against Argentina and try to make it their own,” he said.
“We all know how important a good start against the Pumas will be to our November series, they arrive battle-hardened after a tough Rugby Championship campaign.
“They will be looking to silence the Millennium Stadium crowd from the outset and we know we can't afford to let that happen, with a successful campaign this autumn vital to our ambitions for the future.”
Wales v Argentina: Leigh Halfpenny (Cardiff Blues); Alex Cuthbert (Blues), Scott Williams (Scarlets), Jamie Roberts (Blues), George North (Scarlets); Rhys Priestland (Scarlets), Tavis Knoyle (Scarlets); Gethin Jenkins (Toulon), Matthew Rees (Scarlets), Aaron Jarvis (Ospreys), Alun Wyn Jones (Ospreys), Ian Evans (Ospreys), Josh Turnbull (Scarlets), Toby Faletau (Newport Gwent Dragons), Sam Warburton (Blues, capt)
Replacements: Richard Hibbard (Ospreys), Ryan Bevington (Ospreys), Paul James (Bath), Robin McCusker (Scarlets), Justin Tipuric (Ospreys), Mike Phillips (Bayonne), James Hook (Perpignan), Liam Williams (Scarlets)