Thomas finished with 19 points and 13 rebounds and Bellfield had 15 points for the Rebels (21-7, 9-5 Mountain West).
UNLV missed six consecutive foul shots in the final 8 minutes of regulation but took advantage of a key miss by New Mexico late.
After Gary made just 1-of-2 free throws with 27.2 seconds to put the Lobos up 67-65, Bellfield scored on a layup that forced overtime.
UNLV took a 72-70 lead on Thomas' putback with 2:55 remaining in OT and led the rest of the way.
After a season that saw his shooting numbers slip, should Nigel Hayes return for his senior year at Wisconsin or take the gamble to put him name in this year's NBA draft?
Isaiah Taylor talks about his decision to declare for the NBA draft and what he will miss most about Texas.
Chattanooga women's basketball coach Jim Foster has received a one-year contract extension, the same day the school gave the men's coach a two-year extension.