Joselu came off the bench to drag Newcastle out of even deeper relegation trouble and deny Swansea a major boost to their Premier League survival hopes.
The former Stoke striker, whose B#5million signing in August was symbolic of manager Rafael Benitez's transfer window struggle, stabbed home a 68th-minute equaliser just four minutes after his introduction to cancel out Jordan Ayew's opener.
Newcastle dominated the first half, but squandered a series of chances and might have conceded a penalty before Ayew struck.
But on a day when defeat was simply not an option, they fought back to snatch a 1-1 draw which at least prevented bottom-of-the table Swansea from collecting three points for just the third time in 15 attempts.
Newcastle kicked off having not won a league game at St James' Park since they beat Crystal Palace on October 21, and did so in determined fashion as wide-men Matt Ritchie and Christian Atsu pinned Swansea back.
Indeed, had last season's leading scorer Dwight Gayle been at his best, he might have scored twice within the opening 12 minutes with goalkeeper Lukasz Fabianski diving to his right to claim one header and then looking on gratefully as a second flashed inches wide of the post after Ayoze Perez had bamboozled Kyle Bartley to cross.
Fabianski was called upon once again to keep out Perez's rising 18th-minute drive at his near post after Jonjo Shelvey and Gayle had broken at pace, and was happy to see Paul Dummett's first-time effort fly over his crossbar after Atsu had crossed from the left.
Perez should have scored after being played in by Ritchie with 26 minutes gone, but saw his initial effort saved by the keeper and his follow-up blocked by the covering Ki Sung-yueng, and former Swansea midfielder Shelvey curled a 34th-minute free-kick harmless over after Atsu had been felled inches outside the penalty area.
The visitors threatened twice within seconds when Ki saw a shot blocked and Bartley headed back across goal from the resulting corner where Mike van der Hoorn's flick appeared to hit Mohamed Diame's arm, sparking unanswered penalty appeals.
Bartley headed over from an injury-time corner, but Gayle passed up another opportunity with four minutes of the restart when he dragged a left-foot shot wide after being played in by Perez.
But it was the Swans who were on the front foot as the second half unfolded.
They made the pressure tell with 61 minutes gone when Van der Hoorn's cross evaded Ciaran Clark and although Karl Darlow made a fine save to keep out his initial header, he could not repel his follow-up.
Their lead lasted just seven minutes when substitute Joselu recycled Perez's blocked effort to squeeze a low shot just inside the far post and set up a frenzied conclusion during which Swans substitute Wilfried Bony saw his stoppage-time shot hacked off the line by DeAndre Yedlin.