There are a number of lists of fictional species:

Extraterrestrial

List of fictional extraterrestrials (by media type) Lists of fictional alien species: A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z

Lists of fictional species

Humanoid

Lists of humanoids

Literature

Comics

Television

Film

Video games

Paleoanthropological hoaxes

Cardiff Giant

Nebraska Man

Piltdown Man

Freak show

Humanzee

List of fictional extraterrestrials

Legendary

List of legendary creatures

List of legendary creatures by type

List of giants in mythology and folklore

Vampire folklore by region

Mythical

Legendary creatures of the Argentine Northwest region

Mythical creatures in Burmese folklore

List of Greek mythological creatures

List of legendary creatures from Japan

List of Philippine mythological creatures

Supernatural beings in Slavic folklore

Plants and fungi

List of fictional plants

Reptilian

List of dragons

List of dragons in mythology and folklore

List of dragons in literature

List of dragons in popular culture

List of dragons in film and television

List of dragons in games

List of fictional dinosaurs

Theological

List of fictional angels

List of fictional demons

Lists of fictional species