PLAYA DEL CARMEN, 13 Nov 2014 (AFP) - Finau, in his rookie tour campaign, was level with fellow Americans Hudson Swafford, Robert Garrigus, Will MacKenzie, Steve Wheatcroft and Daniel Berger at the $6.1 million event in Mexico.
Finau, who began on the back nine, took a bogey at the 12th but answered with birdies at the par-5 13th, and par-4 16th and 18th holes, the latter starting a run of four birdies in a row.
After a bogey at the par-5 fifth, Finau finished with birdies at the par-5 seventh and par-4 ninth to grab his share of first place.
One stroke off the pace were another 14 players, including New Zealand's Danny Lee, Australian Aaron Baddeley, Germany's Alex Cejka and American Davis Love.
Home-nation hope Carlos Ortiz was among eight others on 67.
Leading scores on Thursday after the first round of the US PGA Tour's Mayakoba Classic (USA unless noted, par 71):
65 - Will MacKenzie, Robert Garrigus, Steve Wheatcroft, Hudson Swafford, Tony Finau, Daniel Berger
66 - Pat Perez, Davis Love, Brian Harman, Jason Kokrak, Brice Garrett, Shawn Stefani, Alex Cejka (GER), Michael Putnam, Chad Collins, Jason Bohn, Charley Hoffman, Aaron Baddeley (AUS), Danny Lee (NZL), Blayne Barber
67 - Scott Piercy, Patrick Rodgers, Jim Herman, Billy Hurley, Carlos Ortiz (MEX), Robert Streb, Harris English, Justin Thomas