In terrestrial zoology, megafauna (Ancient Greek megas "large" + New Latin fauna "animal") are "giant", "very large" or "large" animals. Their original and most common definition is 100 lb, often rounded in the metric system to 40 or 45 kg.Defense of the Earth. Past consequences of climate change: Evolutionary history of the mammals.Corlett, R. T. (2006). Megafaunal extinctions in tropical Asia. Tropinet 17 (3): 1–3. This thus includes many species not popularly thought of as overly large,… (More on Megafauna)