One of the most fascinating creatures of the ocean is the narwhal. This Arctic whale can be recognized by its unique spiral tusk that extends six to nine feet from its upper jaw (“Morning Edition”). The narwhal's scientific name, Monodon monoceros, means "one tooth, one horn" in Latin. However, the narwhal actually has two teeth and no horns (“Narwhal.org”). In male narwhals, the left tooth develops into a spiral tusk, often mistakenly called a "horn." In rare cases, a double defense will develop. Females generally do not develop tusks. Their teeth generally measure less than 15 centimeters (“Narwhals”). For years, several theories have existed as to why narwhals have horns. Uses on the list include: breaking ice, hunting, defense, transmitting sound, piercing ship hulls, scavenging the seabed for food, and establishing dominance, among others. However, recently, scientists from Harvard and the National Institute of Standards and Technology used an electron microscope to scan a narwhal tusk. They found more than 10 million nerve endings and now believe the tusk is used as a sensory organ to detect changes in salinity and temperature in Arctic waters (Broad). In addition to defense, narwhals have many other amazing physical characteristics, although they are certainly not as prominent as their spiral tooth. Narwhals are stocky creatures with small, round heads. The word "narwhal" comes from the Danish and Norse for "corpse" due to their mottled coloring (Harper). Male narwhals can grow up to 16 feet long (this doesn't include their teeth) and weigh 1.8 tons, while females are slightly smaller at 13 feet and one ton ("Enchanted Learning"). The narwhal is one of three whales (the others being the beluga, and...... middle of document......Coalition, National Council for Science and the Environment). [First published in Encyclopedia of Earth on April 6, 2011; Date of last revision: April 14, 2011; Retrieved August 20, 2011 Ferdinand, Pamela. “A 9-foot flexible whale tooth with super-sensing power?” National Geographic News. National Geographic Society, December 13, 2005. Web. August 20, 2011. .Harper, Douglas. "Narwhal." Online etymology dictionary. 2010. Internet. .Ugly, Kristin. “Narwhal FAQ.” Polar Science Center. University of Washington, nd Web. August 20, 2011. .Perrin, William, Bernd Wursig and J. Thewissen. Encyclopedia of marine mammals. Academic Press, 2008. 787. Print.