Dunshea replaces Crusaders teammate Quinten Strange, who has left the camp after suffering an ankle injury.
Strange is understood to be sidelined for six to eight weeks, effectively ruling him out of the upcoming Bledisloe Cup and Rugby Championship.
Laumape (broken forearm) and Barrett (toe) will have their respective injuries assessed but both are expected to be among the 11 players added to the original 35-man squad, along with Wellington midfielder Peter Umaga-Jensen who is in line to replace the injured Braydon Ennor, for the Rugby Championship.
Coltman has been called in to cover Asafo Aumua who is recovering from a head knock suffered while playing for Wellington. Beauden Barrett is also back the squad following the birth of his daughter, Billie Rose.
Sign up to our mailing list for a weekly digest from the wide world of rugby.Sign Up Now