Of the great apex predators in history, the animal that comes to mind is the huge and terrifying Tyrannosaurus rex . However, this dinosaur, unfairly overrated by many, was not the largest land predator, as claimed; other dinosaurs outnumbered the ‘tyrant reptile’.
It is true that, since the non-avian dinosaurs became extinct, there have been no larger predators in the terrestrial environment. However, large predators are not an exclusive phenomenon of the Mesozoic. Truly colossal predators, such as sperm whales, inhabit the ocean today. And before the dinosaurs, the figure of the apex predator was also present.
The ecological figure of the apex predator dates back to the beginning of the dynamics of predators and prey, during a period of the earth’s history, the Cambrian, more than 500 million years ago.
At the beginning of the Cambrian, a unique evolutionary radiation event occurred in the biosphere. And it is that, although other similar events have happened more recently, none with the magnitude of the great Cambrian explosion. It lasted 12 million years, and skeletons, exoskeletons, shells, teeth, jaws, jointed legs arose… a brief period in the history of life in which evolution ‘went crazy’.
In this period most of the large groups of animals that have survived to this day arose —including vertebrates—, and also many of the ecological dynamics that we know today, including, of course, that of the predator and the prey, which became in one of the most powerful evolutionary engines.
And from that exaggerated evolutionary radiation emerged the first great apex predator. Its name: Anomalocaris , literally, ‘strange crab’, an arthropod belonging to the dinocarids, a group that is now extinct.
Anomalocaris featured a pair of stalked eyes, with up to 16,000 lenses in each eye; he had color vision and depth perception capabilities. This allowed it to easily identify its prey, which it grasped with a pair of spiny appendages. With them it broke the exoskeleton of its prey, if they had one, and sucked the soft parts inside thanks to its mouth cone.
The first estimates of its size, based on extrapolations from different body parts, attributed this animal up to a meter in length. Today we know that it was slightly less than half, but it is still a huge size, considering that it lived in a sea in which most of the animals were smaller than the palm of a human hand – and some, the size of almost microscopic.
To find the next apex predator we must go back to more than 450 million years ago. In the Ordovician oceans, chelicerates—arthropods that have chelicerae as mouthparts, such as modern spiders, scorpions, mites, or Moluccan pans—evolved into many different forms. And a specific group, the eurypterids, became the terror of the seas.
Colloquially known as sea scorpions, they form a large group that, since its origin, in the middle of the Ordovician period, managed to overcome two massive extinctions —the Ordovician-Silurian and the Devonian-Carboniferous— before disappearing at the end of the Permian, during the Great Mortality , along with more than 80% of marine species.
Although no eurypterid remains have been found to preserve identifiable gut contents, their very biology suggests predatory behavior. They featured stereoscopic vision , long front legs with pincers, spines, or even claws. Yes, coprolites have been found —fossil excrements— that are attributed to eurypterids, which reveal the presence of remains of trilobites, other eurypterids, and fish. And it is that, with two meters in length, Pentecopterus decorahensis , from the end of the Ordovician, is not only one of the largest arthropods known, but it was larger than any of the fish of its time.
Much more recently, during the Permian period, between 300 and 250 million years ago, life on earth had already diversified. Much more complex ecosystems dominated the landscape, with abundant biodiversity.
Many of the groups of animals that exist today have their origin in that period, among others the ancestors of mammals. They are the synapsids , misnamed ‘mammalian reptiles’ —because they are not true reptiles, the sauropsids, they belong to a different lineage—. The most famous synapsid is, without a doubt, the genus Dimetrodon , an inhabitant of the Early Permian, which was the apex predator of its time, and some of whose species could exceed three meters in length.
However, at the end of the Permian, with the genus Dimetrodon already extinct, a new animal occupied the ecological niche at the top of the food web: Anteosaurus . Despite its name —saurus comes from the Greek σαῦρος, saûros, ‘lizard’— it is a dinocephalus, belonging to the great group of synapsids, like Dimetrodon, and, therefore, it is not a true reptile either . It is more closely related to humans than to any modern reptile.
Although we do not have complete remains of Anteosaurus, skulls exceeding 80 centimeters in length have been identified. Estimates made with other dinocephalians indicate that their total length must have been around five meters. This would make it the largest known non-mammalian sauropsid .
When it was discovered, it was thought to be an animal with similar habits to today’s crocodiles, which would live in the water and drag prey to it, today we know that it was a much more active creature. Also, like other dinocephalians, it was capable of suddenly projecting its body forward , an ability that other dinocephalians used for head-butting combat, but which Anteosaurus probably employed as a hunting strategy.
Referencias:
Benoit, J. et al. 2021. Palaeoneurology and palaeobiology of the dinocephalian Anteosaurus magnificus. Acta Palaeontologica Polonica, 66. DOI: 10.4202/app.00800.2020
Lamsdell, J. C. et al. 2015. The oldest described eurypterid: a giant Middle Ordovician (Darriwilian) megalograptid from the Winneshiek Lagerstätte of Iowa. BMC Evolutionary Biology, 15(1), 169. DOI: 10.1186/s12862-015-0443-9
Lerosey-Aubril, R. et al. 2018. New suspension-feeding radiodont suggests evolution of microplanktivory in Cambrian macronekton. Nature Communications, 9(1), 3774. DOI: 10.1038/s41467-018-06229-7
Paterson, J. R. et al. 2011. Acute vision in the giant Cambrian predator Anomalocaris and the origin of compound eyes. Nature, 480(7376), 237-240. DOI: 10.1038/nature10689
Selden, P. A. 1984. Autecology of Silurian eurypterids. Special Papers in Palaeontology, 32, 39-54.
