From 2005 through 2008, seven mature female Finetooth Sharks, Carcharhinus isodon, were collected in the central northern Gulf of Mexico between April and June, a time coinciding with parturition and ovulation for the species. Five specimens displayed states of pregnancy and ovarian development consistent with a biennial reproductive cycle. Two individuals had near-term pups and vitellogenic oocytes, a condition indicative of an annual reproductive cycle. These observations are the first report of annual reproduction in Finetooth Sharks and represent the first documented case of intraspecific divergence in the reproductive cycles for any elasmobranch within a discrete area.