I found this possible fossil while working the antarctic a few years ago, and would love to know its significance. It is very solid stone, and was just sitting amongst various rocks quite high up marambio island (also called seymour island), just off the antarctic peninsula. I have attached a few pics. It is around 17cm long and 5cm wide at the base. It could be tooth shaped but if so it might be a large tooth.
Please let me know if you can help, of if you need more info