When you think of sloths, you think of small, furry mammals that move at a leisurely pace. Their ancestors were anything but small! Megalonyx, Greek for Large claw, is an extinct genus of ground sloths that lived on Earth for over 10 million years. They migrated from South America to North America and typically lived near areas with lakes, rivers, and forests.
Ground sloths fared best in warm environments and traveled south when it got too cold in Alaska and the Yukon. These giant animals fared better in habitats that mixed conifer-hardwood and spruce trees. They were nearly 10 feet tall and weighed roughly 2,205 pounds. They were tall enough to perch on their hind legs and feed on trees. They most likely survived up until about 11,000 years ago.
Known as megaloceros, the giant deer was common throughout Eurasia. They lived during the Pleistocene era through the start of the Holocene period. Experts believe these giant deer are related to the modern fallow deer. Like many prehistoric mammals, megaloceros were herbivores and are only plants.
These giant animals enjoyed roaming open woodlands and meadows. Megaloceros is known for being the deer species that were most adept at running. Giant deer averaged a height of 6 feet 7 inches at their withers and had huge antlers, resembling a moose. These antlers were longer than a car and were used to attract female deer. Many fossils have been found in Ireland, but the giant deer did not exclusively live there.
Palaeoloxodon antiquus, or the straight-tusked elephant, inhabited Western Asia and Europe during the Middle and Late Pleistocene era. They thrived in interglacial periods and warmer temperatures. Usually, they traveled in small herds of 5 to 15 individuals. Fossil evidence shows that early humans were predators against straight-tusk elephants.
The palaeoloxodon antiquus was very large and reached up to 13 feet tall. They weighed more than 12 tons and had longer legs than modern elephants. Their tusks curved upwards and they had tongues nearly 3 feet long to be able to grab leaves and grasses while grazing easily. That allowed them to access foliage up to 26 feet above the ground.
Large prehistoric creatures were not limited to land. The jaekelopterus, or giant sea scorpion, is the largest arthropod ever discovered. These creepy creatures resembled giant lobsters and had claws the size of an adult’s head. They were known for being terrors under the water.
Experts estimated these insects grew up to 8.5 feet. Jaekelopterus have an expanded hind segment, large pincers, and long forelimbs. They thrived in freshwater environments and feasted on fish. Fossils show that the size and shape of the giant sea scorpion would have been unable to walk on dry land. High visual acuity and long tentacles make the jaekelopterus skilled visual predators.
The spotted hyena dates back to the Upper Paleolithic period. Cave paintings at Chauvet and Lascaux Caves depict these giant mammals. Native to Sub-Saharan Africa, this species originated in Asia and traveled through Europe for roughly 1 million years until the Late Pleistocene era.
Spotted hyenas still exist to this day, and there’s between 27,000 and 47,000 on the planet. These mammals travel in packs, and their behavior mimics that of baboons and macaque monkeys. Female hyenas dominate the groups and are built larger than the males. Unfortunately, hyenas have a poor reputation for being dangerous, foolish, and stupid, leading to their survival being jeopardized. Hyenas are carnivorous and predatory. Many people believe them to be scavengers, but that’s not the case. These animals eat their prey efficiently, and they can even digest an animal’s bones.
Miracinonyx inexpectatus, also known as the American cheetah, roamed around North America between 2 and 3 million years ago. This mammal was initially thought to be closely related to the cougar, but research shows that they’re more like modern cheetahs.
Unlike modern cheetahs, the American cheetah was best suited for climbing. Their retractable claws and lighter frame gave them an advantage for scaling rocks and mountainsides. They had short legs, making them less fast than the cheetahs we have today. Most miracinonyx inexpectatus weighed around 150 pounds and had a body length of 67 inches. The American cheetah became extinct roughly 12,000 years ago.
Part of the extinct Panthera species is the Panthera spelaea or cave lion. Fossils prove that this large mammal originated in Europe less than 600,000 years ago. Although they share a name, DNA-wise, the cave lion and modern African lion are divergent. The shape of their skulls leads experts to conclude that cave lions are more related to tigers than lions.
Cave art from ancient times depicts cave lions in religious rituals. They were also drawn without manes, so they most likely had no manes or very short ones. Cave lions are regarded as being one of the largest subspecies of lions, reaching heights of nearly 4 feet and body lengths of almost 7 feet. DNA analysis shows that cave lions have similar fur colors and textures to their modern counterparts. These creatures were known for being solitary hunters and survived on a carnivorous diet of reindeer, bison, giant deer and musk ox. It’s hunting competitor was most likely the European Ice Age leopard.
Glyptodons were gigantic versions of the armadillo. In fact, they are known as being cousins of the armadillos we have now. They are also related to tree sloths, anteaters, and extinct ground sloths. Large glyptodons originally came from South America, with fossils being discovered in Argentina, Brazil, and Uruguay.
It has been said that Charles Darwin discovered the first evidence of glyptodon fossils. The glyptodon was large and round, shaped like a flatter Volkswagen Beetle. They were pretty much the same size and weight as the iconic car! These fascinating creatures were round with a bony shell and super short limbs, making them look like a turtle. Based on the shape of their skull and jaw, glyptodons were herbivores. They typically grazed near rivers and lakes, searching for grasses and trees.
Bootherium bombifrons is the scientific term used to describe the regal woodland musk ox. During the Pleistocene era, this large mammal was one of the most prominent musk ox species in North America. Woodland musk ox fossils have been discovered all over the country, including in Alaska, Texas, California, New Jersey, and Oklahoma.
The woodland musk ox is most closely related to the modern musk ox, frequently found in Arctic regions. This species evolved to live best in less frigid climates, which is why it only remained in North America. Bootherium bombifrons were much more significant than their modern descendants, weighing nearly 1,000 pounds. Also, their skulls were thicker, and their snouts were longer. Their horns sat high on the head and curved downwards. Woodland musk oxen ate a diet rich in plants, dining mostly on woody plants, willows and a wide variety of upland grasses.
Most common in Central and South America, the short-faced bear, or Arctotherium angustidens, was present on Earth during the late Pliocene era. These animals are the most closely related to the spectacled bear, a native of South America. Contrary to its name, the short-faced bear did not, in fact, have a little face. Its limbs were so long they made its head look tiny in comparison.
The long appendages of the short-faced bear made them excellent at running. Bears today can run in short bursts, but not for an extended period of time. Arctotherium angustidens were skilled runners and would pounce on their prey like cats. This species weighed between 2,000 and 4,500 pounds, making it the largest bear genus ever discovered and the largest carnivorous land mammal of all time. Experts believe the short-faced bear evolved to be so large because of increased competition from other species like jaguars.
Another member of the Pleistocene megafauna was the woolly rhinoceros. Scientifically known as Coelodonta antiquitatis, these animals most commonly lived in Europe and northern Asia. This animal is the last member of the rhinoceros lineage of the Pleistocene epoch.
The woolly rhinoceros was suited for icy environments. Their stocky legs and woolly fur made it easy for them to withstand freezing tundra conditions. Coelodonta antiquitatis were roughly 9 to 13 feet tall and weighed between 4,000 and 6,000 pounds. They had two keratin horns on the top of their skull and one prominent horn between their eyes for defense. These mammals were grazers and browsers, dining on foliage and other nutritious plants. Woolly rhinos are most closely related to the modern Sumatran rhinoceros.
Research shows that the wild horses living in North America were most likely wiped out by early humans. Toward the end of the Pleistocene era, the extinction of North American horses, mammoths and other large mammals coincided with the Ice Age. These horses, ancestors of modern donkeys, went extinct in North America, but somehow survived in Africa and Eurasia.
The subspecies of the modern horses we know today evolved in North America roughly 1 million to 2 million years ago. Horses began being domesticated by humans starting in 4,000 BC. Fossils indicate that the North American horses went extinct approximately 12,500 years ago. It’s fascinating to imagine the landscape being overrun by majestic North American horses all those years ago.
Mastodons are distant relatives of the wooly mammoth. They migrated to North America via the Bering Strait land bridge roughly 15 million years ago. These creatures were prominent in North and Central America until they went extinct 10,00 years ago due to overharvesting by Clovis hunters.
Typically, mastodons traveled in herds and lived in cold spruce woodland areas. Their eating habits were very similar to modern elephants. They would browse and graze for mixed plants. The bulk of the mastodon diet was coniferous twigs. Mastodons in America had thick, shaggy coats like the wooly mammoth. Their tusks could reach over 16 feet in length and curved slightly upwards. These mammals reached heights up to 9 feet tall and weighed nearly 10 tons.
Known as Smilodon, the saber-toothed tiger most commonly lived in North, South and Central America during the Pleistocene epoch. These animals are notable for their large canine teeth that extend from their mouth. The teeth were used to capture and kill prey quickly and could be as long as 1 foot.
Most saber-toothed tigers are roughly the size of modern cats and built compactly. They had shorter spines, feet, and tails than most felines. Comparable to a jaguar, saber-toothed tigers weighed between 120 and 220 pounds. These mammals were considered apex predators and preyed on large mammals. Bison, pig-like animals called Platygonus and a llama-related creature called Hemiauchenia were targets of the cunning saber-toothed tiger. The dire wolf and American lion were competitors of the saber-toothed tiger. Although it’s named tiger, this mammal is not related to tigers or other modern cats.
Related to modern dragonflies, the Meganeura is the biggest predatory flying insect ever discovered. Its wingspan reaches from 25 to 28 inches. This terrifying insect lived on Earth roughly 300 million years ago. Higher oxygen concentrations in prehistoric times made it possible for this bug to breathe enough to support its size. Luckily, we don’t have to worry about encountering these bugs that are one quarter the size of a human!
Additionally, a lack of predators contributed to the Meganeura being able to evolve to be so large. Scientists also believe that because they were developed in water before appearing on land as adults, they were more equipped to handle high oxygen levels. Meganeura was a predatory species and feasted on other insects. It’s also possible that they ate small amphibians.