Commenting on Jones's selection, Lions head coach Ian McGeechan said: "Ryan Jones has been called up to replace Stephen Ferris who unfortunately sustained a knee injury during Monday afternoon's training. He twisted his right knee in a training drill and following a medical assessment it was decided that he should undergo a scan to determine the extent of the injury."
"He had the scan on Tuesday morning that showed he had a grade two tear to his medial collateral ligament. This usually requires a four to six week recovery period and is severe enough to mean he will miss the rest of the tour. Therefore with six matches left on tour after Wednesday's match against the Sharks we believe we need to fly out a replacement as cover for the backrow."
"Ryan is on the standby reserve list and of course has been playing for Wales over the last few weeks in the USA and Canada. He will fit right in as he knows a lot of the players and of course he was a Lions replacement on the 2005 tour to New Zealand. In fact on that tour he showed how competitive he is as an individual by forcing his way into the Test side for all thee matches against the All Blacks."
Jones's call-up has been described as "A great honour for Ryan and for Wales," by Welsh Rugby Union Group Chief Executive Roger Lewis.
Jones' arrival in South Africa will take the compliment of Welsh international players on the tour to 14, with eight more WRU personnel in the coaching and back room staff including Tour Manager Gerald Davies.
Jones has just returned to Wales after captaining his country to a 100 per cent winning record in the two Test tour of Canada and the USA. And he will fly out to South Africa with Neil Jenkins who this week was called into the squad as kicking coach for the rest of the tour.
Jones said: "I am delighted to have received this call-up and I am just really looking forward to joining the squad later this week. Obviously it is disappointing for Stephen Ferris who is a superb player and I wish him a quick and full recovery from his injury.
"I am anxious to help the Lions in any way I can and I recognise how this is a great honour for me and my family."
Lewis added: "This is a great honour for Ryan and for Wales. He fully deserves his call-up because of his undoubted talent and his superb qualities on and off the field.
"He led the tour to the USA and Canada with great dignity and skill and I know he and all the Welsh players and staff on the tour will give their all to the Lions cause.
"I have spoken to Ryan tonight to wish him well and he is clearly looking forward to what will be a great experience."