This mentioned taxonomy is an attempt to make an conclusive assignment from the different classifications of various scientists. Because the taxonomy may change due to the latest investigative methods and other findings, our map is a guide only.
O. P. Hay, 1902 - - Bibliography and Catalogue of the Fossil Vertebrata of North America. Bulletin of the United States Geological Survey (179), 1-868 (serial monograph, English)
E. D. Cope, 1877 - Report on the geology of the region of the Judith River, Montana, and on vertebrate fossils obtained on or near the Missouri River - Bulletin of the United States Geological and Geographical Survey (3), 565-597 (serial monograph, English)