The 24-year-old Traynor, who won three caps in last November's Autumn Tests, is being added to the squad as a precaution as Gloucester's Alasdair Dickinson has been affected by an abdominal upset.
Traynor, who is currently with the Scotland A squad in Bucharest preparing to launch their defence of the IRB Nations Cup, is expected to arrive in Buenos Aires on Thursday morning.
As a result, Traynor's 25-year-old Edinburgh team-mate David Young, who won his first Scotland A cap two years ago, will now travel to join the Scotland A squad.
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