Cryptozoology (from Greek κρυπτός, kruptos, "hidden" + zoology; literally, "study of hidden animals") is the study of and search for animals which fall outside of contemporary zoological catalogs. It consists of two primary fields of research:

• The search for living examples of animals taxonomically identified through fossil records, but which are believed to be extinct.
• The search for animals that fall outside of taxonomic records due to a lack of empirical evidence, but for which anecdotal evidence exists in the form of myths, legends, or undocumented sightings.Simpson, George G. (1984-03-30) "Mammals and Cryptozoology", Proceedings of the American Philosophical Society, p1, V128#1

Those involved in cryptozoological study are known as "cryptozoologists"; the animals they study are often referred to as "cryptids", a term coined by John Wall in 1983.Coleman, Loren and Clark, Jerome.Cryptozoology A to Z: The Encyclopedia of Loch Monsters, Sasquatch, Chupacabras, and Other Authentic Mysteries of Nature. New York: Fireside/Simon and Schuster, 1999

Because cryptozoologists do not universally follow the scientific method and devote a substantial portion of their efforts to investigations of cryptids that most scientists believe are unlikely to exist,Dash, Mike, Borderlands: The Ultimate Exploration of the Unknown, Overlook Press, 2000 cryptozoology has received little attention from the scientific community. In 2004, however, paleoanthropologist Henry Gee, a senior editor of the leading journal Nature argued that cryptozoology was of legitimate scientific value and could "come in from the cold."

Overview

Invention of the term "cryptozoology" is often attributed to zoologist Bernard Heuvelmans, although Heuvelmans attributes coinage of the term to the late Scottish explorer and adventurer Ivan T. Sanderson. Heuvelmans' 1955 book, On the Track of Unknown Animals, traces the scholarly origins of the discipline to Anthonie Cornelis Oudemans and his 1892 study, The Great Sea Serpent. Heuvelmans argued that cryptozoology should be undertaken with scientific rigor, but with an open-minded, interdisciplinary approach. He also stressed that attention should be given to local, urban and folkloric sources regarding such creatures, arguing that while often layered in unlikely and fantastic elements, folktales can have small grains of truth and important information regarding these organisms. Loren Coleman, a modern popularizer of cryptozoology, has chronicled the history and personalities of cryptozoology in his books.

Another notable book on the subject is Willy Ley's Exotic Zoology (1959). Ley was best known for his writings on rocketry and related topics, but he was trained in paleontology, and wrote a number of books about animals. Ley's collection Exotic Zoology is of some interest to cryptozoology, as he discusses the Yeti and sea serpents, as well as relict dinosaurs. The book's first section ("Myth?") entertains the possibility that some legendary creatures (like the sirrush, the unicorn or the cyclops) might be based on actual animals, through misinterpretation of the animals and/or their remains. Perhaps the most rigorously scientific analyses of cryptids can be found in the works of British zoologist and cryptozoologist Dr. Karl Shuker, who has published 12 books and countless articles on numerous cryptozoological subjects since the mid-1980s.