Hayden Springer carded a round of 59 to forge a two-stroke lead in the first round of the John Deere Classic, while Seamus Power is in a share of eighth after an opening 64.
The world number 236 wrapped up the 14th sub-60 round on the PGA Tour with an eagle-birdie finish – 12 days after Cameron Young added his name to the list at the Travelers Championship.
An eagle and six birdies to the turn meant Springer's 29 was a record for the front nine on the TPC Deere Run course and lowest since 2000 but failing to take advantage of the par-five 10th was the first of five successive pars.
A 59 looked unlikely even after a birdie at the 15th but he holed out from 55 yards for an eagle at the par-five 17th and then nervelessly sank a 12-footer at the last for his place in the history books.
Finland's Sami Valimaki was two shots back after opening with four birdies and finishing with three more, leaving him one ahead of American Eric Cole.
Power's bogey-free round featured five birdies and an eagle on the par-five 17th to leave the Waterford player five shots behind Springer in a group with six rivals.
"I’m at a loss for words at being able to do that, one of the rare things in golf," said Springer, who, prior to his joint-10th place finish at the Rocket Mortgage Classic on Sunday, had missed six successive cuts. "I’ve shot 61 a few times.
"It’s been a little bit tough to find anything, so it is special."
