Joint on selected

import pymel.core as pm

sel = pm.ls(selection=True)
pm.select( d=True )
for target in sel:
	pm.select( d=True )
	newJnt = target.replace("_grp","_skel")
	jnt = pm.joint(n=newJnt)
	pm.matchTransform(jnt, target, pos=True, rot=True)