Los Tirasol Mentir was a male Alonis starfleet officer serving in the late 23rd and early 24th centuries. In 2311, he held the rank of Admiral. He was the second Alonis to ever join starfleet, and his application was sponsored by John "Blackjack" Harriman. Like all Alonis, Mentir enjoyed swimming and would often do so to release stress.
In 2311, Mentir was forced to take over Blackjack's position in the covert plan surrounding the Tomed Incident after Blackjack was critically injured aboard the USS Ad Astra. He recruited Demora Sulu to recover three special operations operatives after the destruction of the IRW Tomed. (ST - The Lost Era novel: Serpents Among the Ruins)
In 2319, Mentir, now the Chief of Starfleet Operations, had moved up the test-bed schedule for the Ambassador-class trials, which would conducted and assess the prototype starship on the brink of Tzenkethi space.
He was informed by Captain Amina Sasine of Admiral John Harriman's actions to use the USS Cassiopeia to rescue the stranded survivors of the USS Excelsior. He then temporarily reassigned Capt. Sasine to the USS Cassiopeia to assist in the rescue effort. (ST - The Lost Era novel: One Constant Star)