Little Colorado River Spinedace

The Little Colorado spinedace is small, generally less than 10 cm in length. The scales are in a lateral line of usually more than 90. The second spine of the dorsal fin is strong. The dorsal fin is moderately high and acute, and its depressed length is 5.2 to 5.8 cm predorsal length. There are eight anal fin rays, and rarely nine. The pharyngeal teeth are in two rows. The Little Colorado spinedace sides are usually silvery, darker above and sometimes white below, rarely with lateral blotches. The upper side and back are a bit of a bluish or lead grey. The breeding Little Colorado Spinedace males have bases of paired fins watery-yellow to orange or red-orange, otherwise however the fins are clear, and parts of the belly are watery-yellow.

The Little Colorado spinedace is endemic to the Little Colorado River and north-flowing tributaries, flowing through Coconino, Navajo, and Apache Counties of Arizona. The historical distribution is similar to the current distribution but the species may have possibly historically occurred in the Zuni River watershed south of Gallup, New Mexico. The Little Colorado spinedace are now considered extirpated from the Silver Creek and its tributaries. Four populations of spinedace exist in Arizona with populations still found in the mainstream of Little Colorado, Nutrioso Creek, Clear Creek, as well as Chevelon Creek.