RT Journal Article SR Electronic T1 Polydactyl horses, recent and extinct JF American Journal of Science JO Am J Sci FD American Journal of Science SP 499 OP 505 DO 10.2475/ajs.s3-17.102.499 VO s3-17 IS 102 A1 Marsh, Othniel Charles YR 1879 UL http://www.ajsonline.org/content/s3-17/102/499.abstract AB