The hardhead is a large minnow, somewhat smaller than the squawfish, seldom reaching lengths of two feet. It has a smaller mouth and a less slender head. It differs sharply in having the upper lip non-protractile (bound to the forehead by a bridge of skin, the frenum) and in having a much shorter bony pharyngeal arch (in the throat), with molar rather than slender hook teeth. These differences in structure indicate that the hardhead is much less predaceous than the squawfish.

The hardhead is probably uncommon within the park and is almost certainly confined there to the lower elevations of the Merced canyon. The warm waters of the Sacramento-San Joaquin drainage throughout their lowland valleys is the native home of this species. This habitat preference makes it rarely taken within the park boundaries. The few that ascend the stream beyond the park boundary are perhaps strays from Indian Flat where many young and yearling specimens and some older ones were taken by a California Division of Fish and Game survey party in 1933. The only specimen known from the park area was taken July 26, 1934, from the Merced River just within the western boundary and is now preserved in the Yosemite Museum collection.