In terrestrial zoology, megafauna (Ancient Greek megas ""large"" + New Latin fauna ""animal"") are large or giant animals. The most common thresholds used are 45 kilograms (100 lb) or 100 kilograms (220 lb). This thus includes many species not popularly thought of as overly large, such as white-tailed deer, red kangaroo, and humans.In practice, the most common usage encountered in academic and popular writing describes land animals roughly larger than a human that are not (solely) domesticated. The term is especially associated with the Pleistocene megafauna – the land animals often larger than modern counterparts considered archetypical of the last ice age, such as mammoths, the majority of which in northern Eurasia, the Americas and Australia became extinct as recently as 10,000–40,000 years ago. It is also commonly used for the largest extant wild land animals, especially elephants, giraffes, hippopotamuses, rhinoceroses, and large bovines. Megafauna may be subcategorized by their trophic position into megaherbivores (e.g., elk), megacarnivores (e.g., lions), and, more rarely, megaomnivores (e.g., bears).Other common uses are for giant aquatic species, especially whales, any larger wild or domesticated land animals such as larger antelope and cattle, as well as numerous dinosaurs and other extinct giant reptilians.The term is also sometimes applied to animals (usually extinct) of great size relative to a more common or surviving type of the animal, for example the 1 m (3 ft) dragonflies of the Carboniferous period.