born , July 28, 1840, Philadelphia, Pa., U.S.
died April 12, 1897, Philadelphia
U.S. paleontologist.
He devoted 22 years to exploration and research, especially in the description of extinct fishes, reptiles, and mammals of the western U.S. He discovered about 1,000 species of extinct vertebrates and developed the evolutionary histories of the horse and of mammalian teeth. His theory of kinetogenesis, stating that the natural movements of animals aided in the alteration and development of moving parts, led him to support Lamarck 's theory of evolution. He engaged in a bitter, long-running feud with O.C. Marsh . Among his 1,200 books and papers are Reptilia and Aves of North America (186970) and Relation of Man to Tertiary Mammalia (1875).