Ashley Richards of Swansea and Bristol City pair Lewin Nyatanga and James Wilson have also been called up by Chris Coleman.
The news follows the withdrawals of Huddersfield defender Joel Lynch and Wolves midfielder Dave Edwards.
Davies, 26, will be hoping to add to his five previous caps when Chris Coleman's side take on Scotland at the Cardiff City Stadium on Friday before travelling to face Croatia the following Tuesday.
Davies, who joined Barnsley from Chesterfield in July 2011, has scored eight goals in 12 appearances for the Tykes this season.
He struck four of those in the space of 19 minutes in the recent 5-0 win at Birmingham to become the first Barnsley player to score four in a match since 1924, when Abe Blight helped himself to that haul against Accrington.
Centre-half Lynch missed Huddersfield's win at Birmingham on Saturday after complaining of a pain during training on Thursday.
It has since been confirmed he has small piece of bone floating in his knee.
"Joel will wear a brace for the next four or five days to help the healing process," Huddersfield manager Simon Grayson told the club's official website.
"He'll return to see the specialist at the end of this week and hopefully will be given the all clear."
Edwards is on paternity leave after racing home before Wolves' win at Blackburn to attend the birth of his daughter.