North America has a wide range of ecosystems including oceans, plains, and frozen tundras. This makes it home to some large and powerful predators. These modern predators like alligators, great-white sharks and even polar bears are compared to the many ancient predators that inhabited North America. What are the biggest predators to have ever lived in North America, then?
Ross MacPhee (senior curator of mammals at American Museum of Natural History, New York City), stated that North America's largest predatory mammal, the massive short-faced bear (Arctodus Simus), was the furry animal of the species. This now extinct animal was affectionately known as the "bulldog bear" because of its distinctive muzzle. According to the University of Iowa Museum of Natural History, it stood approximately 5.5 feet (1.6 m) high at the shoulder and more than 11 feet (3.4 meters) on its long hind legs.
Scientists can sometimes have difficulty estimating the body weight of extinct species because they must extrapolate these numbers using species that are already in use. MacPhee explained this to Live Science via email. Paleontologists believe that the short-faced bear weighed in at around 1,540 pounds (700 kg). According to Polar Bears International, modern polar bears (Ursus martimus) can stand approximately 5 feet (1.25 m) tall at the shoulders and weigh in the neighborhood of 1,300 pounds (660 kg).
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The last time short-faced bears were extinct was 11,000 years ago. This occurred around the end the last ice age. We will have to go further back in history to find a larger land predator. Tyrannosaurus Rex, the most well-known and largest North American predatory dinosaur, is also the most popular: it's the Tyrannosaurus rex.
North America was a land full of monsters during the late Cretaceous period, approximately 100 million to 66 millions years ago. Andrew Farke, the director of the Raymond M. Alf Museum of Paleontology, Claremont, California told Live Science via email that carnivorous dinosaurs were very diverse in North America during the Mesozoic (252 million to 66,000 million years ago). The spiny-backed Acrocanthosaurus was among them, as well as the sharp-clawed Deinonychus and the feathery Microvenator.
T. rex was twelve feet tall at his hips and as long a school bus as it was wide, so he towered above all other carnivores. (Image credit: Shutterstock)
The feared tyrant rex stood tall at almost 12 feet (3.5m) at the hips, and 40 feet (12.3m) at the length of the body, according to Stan, a school bus-sized T. rex specimen. Acrocanthosaurus was a "shark toothed" cousin of Tyrannosaurs and a member of the group called carcharodontosaurs. It weighed 6.8 tons (6.9 metric tons) and was nearly as long as T. Rex (7.8 tons (7.1 metric tons), according American Museum of Natural History. According to a 2019 study published in The Anatomical Record, T. rex made use of all its bulk. It could exert up to 6 tonnes (5.4 metric tons), of pressure per bite, enough to rip through steel like a piece of paper.
Birds are the only living dinosaurs today, and the California condor (Gymnogyps Californianianus) is the largest living dinosaur in North America. This bird measures 10 feet (3 meters) in length from wing tip-to-wing tip. It is smaller than T. rex but it is still a formidable predator, eating carcasses of cattle, deer, pigs, sea lions and whales according to Cornell Lab of Ornithology.
Shonisaurus sikanniensis measured 65 feet in length, three times longer than the longest great white shark. (Image credit: Shutterstock)
A giant reptile is the most famous of all ancient sea behemoths. The Mesozoic era was the time period when the dinosaurs lived, and the Ichthyosaurs were a group predatory marine reptiles. An ichthyosaur, Shonisaurus sikanniensis, was swimming in British Columbia's waters during the Triassic period. This is approximately 237 million years ago.
Live Science was told by Kenshu Shimada (a professor of paleobiology from DePaul University in Chicago) that S. sikanniensis "is regarded as being the largest marine reptile known." It is still a matter of debate whether the S. sikanniensis ichthyosaur genus belonged to Shonisaurus or Shastasaurus. According to Mark Witton, University of Portsmouth paleontologist, and paleoartist, both genera had large, agile, and fast members. However, Shonisaurus species had long snouts and barrel-shaped chests, as opposed with the shorter, more muscular Shastasaurus.
No matter what taxonomy you use, it is clear that S. sikanniensis was a massive shark. It measured 65 feet (20 meters) from tail to snout, which Shimada stated was "easily three times larger than the largest living great white shark." But size doesn't always equal ferocity. According to a 2011 study published in PLOS One, S. sikanniensis might have been a suction feeder that slurped up soft-bodied prey like squids or belemnites (shelled Squids).
However, each of these creatures eventually died due to environmental change. As with many highly skilled predators, when their prey became scarce, their energy requirements were too high. MacPhee stated, "At some point, bigger isn't better."
Original publication on Live Science
