With Ulster’s fortunes at the scrum not improving in the early moments of the second half, Murphy replaced both his starting props, bringing on Tom O’Toole and Andy Warwick to try and steady the ship.
Glasgow would see a Rory Darge score ruled out for a forward pass in the build-up and, despite being the better side, as the game neared the final quarter, still only led by two.
Tom Jordan’s yellow card for a dangerous ruck entry gave Ulster a way back into the game with the numerical advantage sparking their best passage of the game.
But while they forced Glasgow into yet more penalty concessions, eventually drawing a yellow for Richie Gray, they were held up over the line when attacking against 13.
Jordan returned but, after a full 15 minutes of pounding the Glasgow line, Ulster eventually found a way over with Dave McCann crashing over a mass of bodies to ground the ball.
But Glasgow struck back almost immediately, with Kyle Steyn finishing off a move in which Franco Smith’s side made light of their numerical disadvantage.
With Gray returning to the field just as replacement Adam Hastings added the extras, Ulster were left needing a try in the final moments.
After four full minutes of added time, they thought they had it when Shanahan found the whitewash but the drama was not yet finished.
A lengthy discussion between the officials to ascertain whether Shanahan had knocked on before grounding followed with the decision to award the score sparking huge celebration in the stands.
Ulster: McIlroy; Lowry, Moore, Postlethwaite, Stockdale; Morgan, Doak; O’Sullivan, Andrew, Barrett; Henderson (capt), Treadwell; McNabney, McCann, Timoney
Replacements: McCormick, Warwick, O’Toole, Sheridan, Izuchukwu, Shanahan, Humphreys, Kok
Glasgow: McKay; Cancelliere, McDowall, Tuipulotu, Steyn (capt); Jordan, Dobie; Bhatti, Matthews, Talakai; Williamson, Gray; M Fagerson, Darge, Venter.
Replacements: Hiddleston, McBeth, Z Fagerson, Samuel, Brown, Ferrie, Afshar, Hastings.
Yellow cards: Jordan, Gray
Referee: Adam Jones
