** Shares of IT services co Grid Dynamics GDYN.O rise 12% at $23 in extended trading
** S&P Dow Jones Indices after market close on Thursday said GDYN will replace Revelyst GEAR.N in S&P SmallCap 600
** Up to last close, stock up 58% YTD
(Reporting by Anshuman Tripathy)
((Anshuman.Tripathy@thomsonreuters.com))