The Irishman and compatriot Rory McIlroy were in fits of laughter after the former’s blunderShane Lowry(Image: Getty Images)

Bemused Shane Lowry admits his spinning Oakmont head caused him to make one of the stupidest mistakes of his career.

The Irishman and his playing partners Rory McIlroy and Justin Rose were left in fits of giggles after the bizarre error during round two of the US Open.

Beaten and pummelled by the brute course, Lowry walked onto the 14th green to mark his ball for a putt, only he forgot to put down a coin and just picked it up.

Frozen in shock for a second at his mad moment, he says caddie Darren Reynolds just looked at him before the laughter started amongst the Ryder Cup trio and the one-stroke penalty was immediately imposed.

Lowry said afterwards: “Probably one of the stupidest things I’ve ever done. I picked the ball up, had the ball in my hand, turned around to Darren and he basically said to me: What are you doing? By then maybe my mind was somewhere else.”

Golf rules state: “If the player lifts the ball without marking its spot, marks its spot in a wrong way or makes a stroke with a ball-marker left in place, the player gets one penalty stroke.”

Lowry was smiling about it, but there were grimaces throughout the day as he collapsed out of the event with a whopping score of 17-under over par.

Asked what had gone wrong, Lowry said: “I don’t know to be honest. I drove it in play a lot Thursday, did what I was supposed to do off the tee and then just didn’t have my game that I’ve had for the last while.

“Then I really struggled on the greens and the round got away from me out here and that was it.

“They let it sort of do what they said it wouldn’t do, but that’s all fine, that’s the US Open.

Rory McIlroy and Shane Lowry(Image: Getty Images)

“I just made obviously too many doubles, too many big mistakes and then when I got a couple chances, I didn’t convert them.

“I didn’t really do much right to be honest, other than I drove the ball as good as I’ve probably driven the ball in a long time. So, yeah, weird couple of days.”

Lowry’s early exit was on the cards long before his marking mistake and the Ryder Cup star has been joined on the weekend scrapheap by a number of his European colleagues.

Ludvig Aberg was unable to do enough to stay in the event and is headed home just like Tommy Fleetwood, who fell away late on Friday to finish at nine-over par.

Rose is also packing up and heading out of Oakmont having combined with Lowry for a combined score of 31-over, whilst Sepp Straka, twice a winner on the PGA Tour this season, misses out on the weekend having finished up at 11-under par.