Genus Knightia, Family Clupeidae, Sub-Family Pellonulinae, is found from the Middle Paleocene to Middle Eocene age fresh water lacustrine formations of western North America and possibly China.  Knightia is the most common vertebrate fossil found in the Wyoming lagerstätte.  Paleontologists recognize three species of Knightia from western North America.

Knightia eocaena (Jordan 1907)  Knightia eocaena is generally the larger of the three Knightia species.  The species may be differentiated by the ratio of body depth to body length.  Knightia eocaena will have a body depth less than 1/3 of "standard length."*

Knightia alta (Leidy 1873) has a body depth over 1/3 of "standard length."*

Knightia vetusta (Grande 1982) is a late middle Paleocene species described from Powder River County, Montana.

*Standard length is measured from the beginning of the head (tip-of-nose) to the end of the vertebra column, not the tips of the tail (caudal) fin.