Morton inflicted Queen of the South's first league defeat of the season with a stunning 5-0 win at Palmerston in the Ladbrokes Championship.
Ross Forbes, Jamie McDonagh, Gary Oliver, Jai Quitongo and Thomas O'Ware (penalty) all struck for Jim Duffy's men in Dumfries.
Hibernian moved to the top of the table on goal difference after a 0-0 draw away to Raith Rovers. Hibs had Marvin Bartley sent off before half-time but Rovers couldn't take advantage and have dropped out of the top four.
A crowd of 6,377 saw Falkirk beat Dunfermline Athletic 2-1 to move to within a point of the summit. Craig Sibbald and Myles Hippolyte scored for the Bairns, with Farid El Alagui pulling one back for the visitors.
Dundee United are into the play-off places after beating bottom club St Mirren 2-0 in Paisley with goals from Scott Fraser and Tony Andreu. The visitors had Mark Durnan sent off in the closing minutes.
Alan Forrest grabbed a hat-trick, the third goal coming via the penalty spot, as Ayr United won 3-0 away to Dumbarton.