The tide turned dramatically though and substitute Ross MacIver equalised with his first touch.

Morton came close on several occasions before Jak Alnwick secured the extra point by stopping Josh McPake's penalty.

St Mirren moved ahead of Queen of the South on goal difference on seven points with the Dumfries side having played all their games.

Victory over Queen's Park will seal top spot with Morton and Partick Thistle two points adrift ahead of their meeting.

Aidan McAdams made a decent early save from Obika and an excellent diving stop from Junior Morias as Morton camped in their own half.

Saints full-back Richard Tait escaped with a yellow card for what Morton's Lewis Strapp claimed was a punch in his ribs.

Kyle McAllister then split the visiting defence with a brilliant through ball but McAdams blocked Obika's shot with his foot.

The visiting goalkeeper spilled a McAllister free-kick that jumped off the skiddy surface right in front of him but the visitors cleared as Conor McCarthy tried to force home the loose ball.

The chances kept coming for Saints. Marcus Fraser could not get enough contact on Brandon Mason's deep cross to convert from close range, and Sam Foley saw a shot deflected just wide.

The pressure paid off when Obika got above his man to head home McAllister's inswinging corner.

Foley volleyed not far over just after the break but the game unexpectedly turned in Morton's favour. Aidan Nesbitt forced a save with a chip which Alnwick touched over.

On-loan Motherwell forward MacIver, watched by Fir Park assistant manager Keith Lasley, then headed home from close range to level the scores.

Alnwick and Cameron Salkeld wrestled in the penalty box after the Morton forward went in late on the goalkeeper. Salkeld was the only player booked.

Strapp headed over from six yards and substitute McPake beat a man and fired inches wide of the far post as Morton pushed for a winner.

Saints had some late chances with Dylan Connolly's shot saved and Mason firing across face of goal.

Saints striker Kristian Dennis and Morton's Kyle Jacobs were the fall guys as the shoot-out started with two saves before a string of impressive efforts ended when Alnwick stopped McPake's strike.