RIO GRANDE, March 8, 2012 (AFP) - Jones, whose best US PGA finishes were shares of fourth at the 2008 Honda Classic and Buick Open, shared the top spot with American George McNeill, each one stroke ahead of American Ben Curtis, the 2003 British Open champion.
Jones eagled the par-5 second half and parred his way to the ninth, where he began a run of three birdies in a row that ended with his lone bogey of the day at the 12th.
The Aussie added birdies at the 15th and 18th, the two par-5s on the back nine, to finish on six-under.
McNeill, who began a bogey-free round on the back nine, started a run of three birdies in four holes on the 12th and matched the run on the front side with birdies at the par-5 second and fifth around another at the fourth.
Americans Todd Hamilton, Daniel Summerhays, Jeff Overton and Kevin Kisner shared fourth on 69.
Former Masters champion Angel Cabrera opened with a 69 to share eighth after the first round of the $3.5 million event.
Japan's Ryo Ishikawa, who has accepted a special invitation to play at the Masters, shared 21st after an opening 70.
While six major winners were among those chasing the $630,000 top prize, most of the world's top players were playing this week at the World Golf Championships event at Doral in Miami.
Scores on Thursday after the opening round of the $3.5 million Puerto Rico Open (par 72, USA unless noted):
66 - Matt Jones (AUS), George McNeill
67 - Ben Curtis
68 - Jeff Overton, Kevin Kisner, Todd Hamilton, Daniel Summerhays
69 - Lee Janzen, Gavin Coles (AUS), Angel Cabrera (ARG), Shaun Micheel, Mathew Goggin (AUS), Kevin Stadler, Scott Brown, Roland Thatcher, Brendon de Jonge (ZIM), Roberto Castro, Graham DeLaet (CAN), Brian Davis (ENG), Will Claxton
70 - James Driscoll, David Mathis, Hunter Haas, Boo Weekley, Mark Anderson, Henrik Stenson (SWE), Nicholas Thompson, J.J. Killeen, Brendon Todd, Ryo Ishikawa (JPN), Vaughn Taylor, Jamie Lovemark, Danny Lee (NZL)