Evarra tlahuacensis was a species of minnow-like, ray-finned fish in the family Cyprinidae, native to Mexico. It was listed as extinct in 1986 – along with E. eigenmanni and one other species in its genus – most likely due to degradation of its habitat as a result of urbanization. This specimen from the Field Museum in Chicago is the only one in existence. It was collected in 1901 outside of Mexico City by Dr. Seth Meek, one of the museum’s first fish curators. Evarra eigenmanni shares a very similar story to E. tlahuacensis and the museum also has just one specimen of E. eigenmanni.

“This little brown fish in this jar is our only record that this species ever lived on the planet, “explains Dr. Caleb McMahan, Fishes Collections Manager at the Field Museum. “So if one’s interested in trying to figure out why this thing went extinct, they would have to come here and look at this specimen to start the quest of figuring it out.”

McMahan and his collaborators are currently working on a project to return to E. tlahuacensis’ original habitat to compare Meek’s findings with the current status of other, similar species in the area.

A freshwater species native to southwest Mexico, the tequila splitfin (Zoogoneticus tequila) has been reintroduced to the wild in the state of Jalisco after being declared extinct in 2003. Ten pairs of these fish were received by the Michoacán University of Mexico’s Aquatic Biology Unit from the Chester Zoo, UK in 1998, founding a new captive-reared colony that grew quickly. “It very much goes to show that animals can re-adapt to the wild when reintroduced at the right time and in the right environments. Chester Zoo’s mission is to prevent extinction and that’s exactly what we’ve done here,” says Dr. Gerardo Garcia, Curator of Lower Vertebrates and Invertebrates for Chester Zoo.