PROF. H. F. OSBORN has just described a water-worn small molar tooth from a Pliocene formation in Nebraska, U.S.A., as the first evidence of an anthropoid primate discovered in the New World. The specimen was found in the Snake Creek beds by Mr. Harold J. Cook, who has already made known numerous important remains of Pliocene mammals from Nebraska, some showing marked Asiatic affinities. With the aid of Drs. W. D. Matthew, W. K. Gregory, and M. Hellman, Prof. Osborn has determined the tooth to be a second upper molar, and he has named the unknown genus and species to which it belonged Hesperopithecus haroldcookii. It is nearly as large as the second upper molar of an American Indian, and its two diameters are almost equal. The kind of wear shown by its evenly concave coronal surface “has never been seen in an anthropoid tooth.” In type the tooth is “very distant” from the corresponding tooth of the gorilla, gibbon, and orang; it is “still very remote” from that of a chimpanzee. It is also “excluded from close affinity to the fossil Asiatic anthropoid apes” represented by teeth found in India; and “it cannot be said to resemble any known type of human molar very closely.” Indeed, “it is a new and independent type of Primate, and we must seek more material before we can determine its relationships.”
H. F. Osborn, "Hesperopithecus, the first Anthropoid Primate found in America," American Museum Novitates, No. 37 (reprinted, without figures, in Science, vol. 55, PP. 463–465, May 5, 1922).