No, most newly-discovered animals weren't cryptids.
'Cryptids' are legendary creatures that have been rumored in folklore, which some people choose to believe are real despite a total lack of material evidence.
Using the classification proposed by Eberhart it looks like bigfoot could go either way. The classifications do seem to include some proven species as cryptids. It looks as though one could argue that apemen are known from the fossil record and be considered a cryptid on the basis it is believed to have survived to present day. Or it could be argued to not be a cryptid because it is a bizzare human or wildman covered in hair.
http://en.wikipedia.org/wiki/Cryptid
George M. Eberhart of the American Library Association,[9] who has written for the Journal of Scientific Exploration on the difficulties of cataloging media materials about fringe science, classifies ten types of mystery animals under the cryptozoological umbrella:
Distribution anomalies [known animals reported outside their normal range, e.g. the anomalous big cats of the U.K.];
Undescribed, unusual, or outsized variations of known species [e.g. the giant anacondas reported from Amazonia or the spotted lions of East Africa];
Survivals of recently extinct species [e.g. Ivory Billed Woodpecker presumed extinct ca. 1960, or the Steller's Sea Cow presumed extinct ca. 1770, both of which are occasionally claimed to have survived to the present];
Survivals of species known only from the fossil record into modern times [e.g. the mokele-mbembe of central Africa, sometimes described as a living dinosaur];
Lingerlings, or survivals of species known from the fossil record much later into historical times than currently thought [e.g. the woolly mammoth, presumed extinct ca. 12,000 BCE but occasionally purported surviving into later eras];
Animals not known from the fossil record but related to known species [e.g. the Andean wolf or the striped manta-ray reported by William Beebe in the 1930s];
Animals not known from the fossil record nor related to any known species [e.g. North America's Bigfoot or most sea serpents];
Mythical animals with a zoological basis [e.g. the Griffin, partly inspired by dinosaur fossils of Central Asia];
Seemingly paranormal or supernatural entities with some animal-like characteristics [e.g. Mothman, Black Dogs or some fairies from folklore];
Known hoaxes or probable misidentifications [e.g. the Jackalope, an antlered rabbit created as a hoax or prank but possibly inspired by rabbits infected with Shope papilloma virus, which causes antler-like tumors].
Additionally, Eberhart argues for six exclusions from classification as a cryptid:
Insignificance. "Cryptids must be big, weird, dangerous or significant to humans in some way."
Lack of controversy. "Someone needs to observe a mystery animal and someone else needs to discredit the sighting. Cryptozoologists function as interventionists between witnesses and skeptical scientists."
Erratics. "The out-of-place alligator […] that turns up in an odd spot, undoubtedly through human agency, is not a zoological mystery […]
f someone discovers a new species of alligator that lives only in sewers, that is a different matter."
Bizarre humans [e.g. zombies]
Angels or demons […] "the paranormal or supernatural is admitted only if it has an animal shape (a werewolf sighting, which might involve a real dog or wolf, or a mystery canid)."
Aliens "[unless such extraterrestrials] arrived a long time ago and thus classify as residents."
