narwhal

sarvivalas Monodon monoceros, an Arctic cetacean that grows to about 20 feet (6 meters) long, the male having a single horn-like tusk, a twisted, pointed canine tooth that projects forward.
1986, D. E. Sergeant, Chapter 16: Sea Mammals, I. P. Martini (editor), Canadian Inland Seas, http://books.google.com.au/books?id=7gdD_63jN8UC&pg=PA337&dq=%22narwhal%22%7C%22narwhals%22&hl=en&sa=X&ei=OUw5U4rbIMWRkAWXw4HYCQ&redir_esc=yv=onepage&q=%22narwhal%22%7C%22narwhals%22&f=false page 337,

Moreover, both narwhals and bowheads can occur in late summer in southern Prince Regent Inlet (coming from Lancaster Sound) and may reach Fury and Hecla Strait and northern Foxe Basin.

Often, in the morning, narwhals played around the boat and reminded me of the dolphins, so far away in the North Atlantic. But these narwhals were not like the Atlantic sea-dogs; they had little of their flashing vibrancy; these Turkish narwhals were much more relaxed, and rolled over lazily, with a sigh, as if they were going to retire to a sofa and smoke a hookah.

At over 2.5 m in length, the tusk of the male narwhal (Monodon monoceros) is one the most impressive instruments of male-male competition among mammals.