Snicko displayed a spike of noise as the ball passed the glove (of Stoneman's bottom hand) and Dar ruled there was conclusive evidence - and overturned Erasmus' call.
Viewers - Australian and English - took to Twitter to express their surprise at Dar's bizarre decision.
Stoneman had earlier been subjected to a barrage of brutal short-pitched bowling from Starc and Josh Hazlewood and was struck on the helmet by the latter in the afternoon session.
He was struck on the side of the helmet, with the protective stem-guard breaking off as a result of the impact, AAP reported.
The tourists' team doctor assessed the 30-year-old for concussion and checked his jaw before clearing him to continue batting in a new helmet.
"It has to rattle you as a batter. It definitely has to rattle you," Kevin Pietersen said on the Nine Network.
"There is a little cut there you can see on his right jaw.
"That's hit him hard. I really hope he is OK ... it made a horrible noise."
The build-up to the test was overshadowed by a report of attempted match-fixing.
The Sun that two Indian bookmakers had asked undercover reporters for up to £140,000 ($268,000) to fix passages of play, such as the number of runs scored in a given over.
The International Cricket Council's Anti-Corruption Unit later said it couldn't find any evidence that any players had been approached.
