Keystone species mussel population explodes uncontrollably, driving out most other species. These creatures need not be apex predators. Sea stars are prey for sharks, rays, and sea anemones. Sea otters are prey for orca. The jaguar, whose numbers in Central and South America have been classified as near threatened, acts as a keystone predator by its widely varied diet, helping to balance the mammalian jungle ecosystem with its consumption of 87 different species of prey. The lion is another keystone species. Keystone mutualists are organisms that participate in mutually beneficial interaction and the loss of which would have a profound impact upon
Apex predator an environment is suggestive. "Anomalocaris" was an aquatic apex predator, in the Cambrian. Its mouthparts are clearly predatory, and there were no larger animals in the seas at that time. Carnivorous theropod dinosaurs including "Allosaurus" and "Tyrannosaurus" have been described as apex predators, based on their size and dietary needs. A Permian shark, "Triodus sessilis", was discovered containing two amphibians ("Archegosaurus decheni" and "Cheliderpeton latirostre"), one of which had consumed a fish, "Acanthodes bronni", showing that the shark had lived at a trophic level of at least 4. Among more recent fossils, the sabre-tooth cats, like "Smilodon", are considered to