Mexican Stoneroller

The Mexican stoneroller has a very stout body with a very large head and snout. The mouth is unique in that its teeth have cartilaginous sheaths, while the size of its mouth is usually very small. The fish's mature length can range anywhere from 3 to nearly 6 inches, however 6 inches is rare, and the average is about 3.5 inches. They have small scales that run along the lateral line, much like the Gila longfin dace and the Yaqui longfin dace. The scales of the Mexican stoneroller can sometimes form arches on its back. Sexual selection has dictated exaggerated male characteristics, which include larger heads and pre-dorsal areas in more successful males. These fish have color patterns with lighter bottoms and darker backs, with a distinct black stripe along the lateral line. They also have a somewhat blotched appearance.

The Mexican stoneroller has been found as far as south as the Rio Yaqui drainage in Mexico and tributaries of the Rio Grande near the Big Bend region of Texas. The habitat of the Mexican stoneroller ranges in elevation between 2600 and 6500 feet.

Very few studies of the reproduction of this species have been conducted, leaving a limited amount of information about their patterns. This species is capable of changing the colors on its fins during breeding. The color changes are more dramatic in males, due to sexual selection and female mate choice. The winter and late spring months seem to be the primary times in which the bulk of spawning occurs. Mexican stonerollers use their tubercles as weapons during male-to-male competition, and also to stimulate and attract females. The name stoneroller was given to the genus because males excavate breeding areas by rolling stones with their heads to invite the females. This also helps males defend against their rivals.