Shevlin took the responsibility for the spot-kick, sending Rohan Ferguson the wrong way to notch his third goal of the campaign.
Earlier, Ferguson had to be alert to divert on-loan Hamilton Academical midfielder Connor Murray’s long range effort past the post while opposite number Rory Brown proved his worth at the other end.
He got down low at his near post to deny former Coleraine winger Conor McKendry midway through the opening half and was again equal to the task to prevent Jordan McEneff levelling just before half-time.
Larne boss Tiernan Lynch rang the changes during at half-time and it was one of those subs, Ryan, who hauled his side level with 20 minutes remaining.
McKendry was brought down inside the penalty area and Ryan, hat-trick hero in Europe just days earlier, made it four goals in two games with an emphatic finish from 12 yards.
Benji Magee almost made it two goals in as many minutes - only a smart save with his foot from Brown denying the former Loughgall man his first Larne goal.
The home side passed up a glorious chance to score a late winner but Rhyss Campbell was unable to connect with Jack Scott’s cross to the back post and the chance was gone.
So, it’s a point on the road for the league champions as they set out to defend the Gibson Cup.