In our previous two articles about the ice age, we introduced some hopefully interesting information about that cold period of Earth’s history and some of the extinct, yet majestic, animals that roamed the Earth during it.
All of that was inspired by the great animated film series Ice Age, which nailed it by combining fantasy and facts and taught us a lot about our planet through fascinating stories.
If you remember closely, the ice age, the real one, not the film, was one of the main characteristics of Earth’s geology. Thanks to tiny changes in the atmosphere that piled up over millions of years, our dear planet experienced a drastic drop in temperatures, allowing ice sheets and glaciers to form and cover most of the land.
According to scientists, Earth has gone through five major ice ages that were separated by periods of warm climates.
During some of the oldest ice ages, many prehistoric animals managed to survive for millions of years, despite the cold. But for some reason, or reasons, they had to meet the fate of extinction and completely disappeared a few thousand years ago.
In our second article of this series, we talked to you about Manny from the Ice Age film or the mammoth in real life. In today’s article, we are introducing two other main animal characters in the film, Sid and Diego, who happened to be a ground sloth and a smilodon in real life.
So without any further do, let’s hop into it.
Diego the Smilodon
The body is super large and covered with thick, ginger fur. The eyes are intense but may sometimes look kind. The nose is triangular and flattened. The canine teeth are as long and sharp as they are scary, while the ears are ridiculously small. The mane is fluffy and brown and runs from the back of the head down to the back, and the tail is thick and long and is there to help keep the balance.
We are talking about Diego and Diego was a smilodon.
The smilodon was a large cat though not closely related to any of the large cats we are familiar with, such as the lions, cheetahs, jaguars, and pumas. It was mainly characterised by two prolonged canine teeth known as sabre teeth.
Though extinct for over 10,000 years, the smilodon appeared on Earth around 2.5 million years ago. By that time, the dinosaurs had already disappeared some 62 million years earlier, and the mammoths were already roaming the planet.
Like many other prehistoric animals, the smilodon thrived for so long before it was wiped out. Unlike the dinosaurs that lived on all continents and the mammoths that moved between Africa, Europe, Asia, and North America, the smilodon initially appeared in North America and, from there, immigrated to South America.
Like many other extinct animals whose fossils were well hidden in nature, we humans did not know about the smilodon until recently. It was just the first half of the 19th century when Danish Naturalist Peter Wilhelm Lund found the animal’s fossils in some caves in Brazil. When he examined those fossils for the first time, he thought they belonged to a hyena.
But when he studied the bones from other body parts, he concluded they must have belonged to a distinct, yet unknown, animal. This animal, he thought, looked like modern-day big cats but was larger and more robust. And for some reason, he still thought it was somehow related to hyenas.
The Danish naturalist named the animal smilodon. This name is, in fact, a combination of two Greek words that together mean teeth that look like a double-edged knife. He also called it populator, which meant the devastator. I personally do not think any other names could be more descriptive!
Interestingly, none of the fossils that Danish naturalist collected were complete skeletons. Yet, he did collect parts that belonged to different individuals to make up a full skeleton and closely studied it.
Later on, more fossils of the same animal were discovered in North America in the same century. Scientist Joseph Leidy, the one who discovered the first North American smilodon fossils in a cave in Texas, USA, thought at first they were of an animal as ‘cat’ as the lion or the cheetah.
But after some close examinations, he discovered how different they were from those of a lion or a cheetah. That meant they must have belonged to a distinctive predator that no one was aware existed. So he called it Trucifelis fatalis, which meant ‘deadly’, of course, thanks to its super long canine teeth.
After that, more and more smilodon fossils were found in Pennsylvania, USA. After examination, scientists could spot some differences between them and those found in Texas. One main difference was that the canine teeth were short and had a disparate structure.
So scientists classified those Pennsylvania fossils as a distinct species and named it smilodon gracilis, which meant lightly built teeth. That said, scientists could not find as many remains of the smilodon gracilis and barely found complete skeletons.
So to recap, three smilodon species were identified as follows.
- Smilodon populator: that was found in Brazil and is the largest of the three.
- Smilodon fatalis: that was found in a cave in Texas, USA, in 1869. It was the oldest of three though the second to be identified.
- Smilodon gracilis: it was found in a cave in Pennsylvania, USA and was the smallest of them all.
All those three species emerged from one another. So they had similar body structures, yet their body measurements differed.
The South American smilodon gracilis was the smallest species. It weighed 77.5 kg on average. The fatalis was second in line after the gracilis, weighing between 160 and 280 kg. It was as tall as 100 cm at the shoulders and had a body length of 175 cm. Its body was stronger than that of a tiger.
The North American smilodon populator was the largest and one of the most giant cats that ever lived on Earth. It was 120 cm tall at the shoulders and weighed 310 kg on average. Scientists do believe it may have reached the weight of 436 kg.
Smilodons were apex predators. That means they fed on other animals but no other animal fed on them.
Interestingly, the three smilodon species seemed to have different food preferences, most probably because they lived in different habitats. What was common among them was that they typically hunted large animals, possibly larger than themselves. But thanks to their canine teeth, they were able to bring them down.
For instance, the North American smilodon fatalis was thought to feed on bison, camels, deer, and tapirs. The smilodon gracilis, which also lived in North America, fed on peccaries—these were hooved animals that looked like pigs but were not pigs—and other prehistoric llama-like animals.
If you remember from above, the smilodon populator, the first to be found of all the species, immigrated to South America. As the new habitat was different and the food available in the northern continent was absent in the south, the smilodon populator could adjust its diet based on what was then available.
So instead of bison, camels, deer, and tapir, the smilodon populator fed on other prey whose names are pretty hard to pronounce! But one of them was a prehistoric reptile that looked like an alligator.
With all that considered, scientists believe that the differences in the body structures and measurements among the three species may partially be attributed to their different diets.
Deciding why the smilodon went extinct was difficult for scientists because not enough fossils, especially complete skeletons, were found. That is why there are many speculations about what wiped that predator out.
Some of the suggested reasons for why this happened include the following:
- Competition with humans.
- Competition with other big cats.
- Climate change.
Sid the Ground Sloth
Though Sid was not the first character to appear in the 2002 Ice Age film—Scrat, the imaginary squirrel/rat was—it was the first to appear on Earth in comparison with the mammoth and the smilodon. This happened some 35 million years ago, so, technically, Sid was older than both Diego the smilodon and Manny the mammoth.
Sid was a ground sloth. He was a member of a large family of ground sloths that are now extinct—we will give a quick overview of them in a bit. As you might have guessed, it was a bipedal as it used to walk on its hind legs, unlike the modern-day tree-dwelling sloth that barely gets to the ground, if not at all.
Ground sloths were characterised by their large bodies; some species were as giant as an elephant. And like their tree-dwelling relatives, ground sloths used to have long claws which allowed them to pick up and cut leaves on which they fed. Some species’ claws were curved, while others had theirs flattened.
There are six species of tree-dwelling sloths, categorised as two-toed and three-toed. The ground sloth, on the other hand, had way so many species, too many that they belonged to over 80 genera that were classified into different families.
But before we move any further, let’s pause for a second and understand what genera and families mean.
If you quite recall from our previous articles on animals, the taxonomy hierarchy is used to classify all organisms. It has eight levels, arranged from the broadest, known as domain, to the most specific, called the species. Between these top and low levels are the kingdom, phylum, class, order, family, and genus.
Scientists could identify six families of ground sloths divided into as many as 80 genera (plural of genus), to which at least 80 species belonged. Some believe there are over 100 ground sloth species.
The six ground sloth families are as follows.
- Megalonychidae: this was the first ground sloth family to appear on Earth, precisely in North America, about 35 million years ago. They were small, but they grew bigger with time.
- Megatheriidae: this family appeared around 30 million years ago in South Africa. Members of this family were super large and robust.
- Nothrotheriidae: this family dispersed in both North America and South America.
Like many prehistoric animals, ground sloths managed to survive on Earth for millions of years. Yet, their existence had to come to an end around 11,000 years ago.
Like with the case of smilodons, scientists are not quite sure what caused the global population of ground sloths to disappear. Some claim that humans hunted them to extinction. Others believe other factors, such as predator attacks and climate change, might have also contributed to their disappearance.
That first humans hunting ground sloths theory was supported by what scientists learned about them, the sloths, from their fossils. For instance, ground sloths were herbivores. They fed on leaves, grass, and shrubs which were found in open fields. Being in open areas apparently made them quite visible and, therefore, an easy target for humans.
Another point that supports that claim is how the ground sloths moved. Scientists believe they walked on their back legs and knuckles like monkeys and gorillas. Yet, ground sloths were in no way as light as monkeys. Many of their species were massive and may have weighed over 2,000 kg. Such heavy bodies must have made it super hard for the ground sloths to move fast to escape any attacks.
Having said that, these two theories are not certain because some other facts do refute them. The first of those facts is also related to the sloths’ large bodies which should have provided protection. If some species were as large as elephants, how could humans take them down?
Another fact is related to the ground sloths living with many large predators around. Despite that, the sloths managed to stick around for millions of years. How, then, could the sudden appearance of a predator species threaten the ground sloths and bring their population to an end?
One thing that scientists may be sure about is the order in which the different ground sloth species went extinct. They reported that the North and South American species disappeared first. But those that lived in Central America survived for some four or five thousand years more before they, too, eventually disappeared.
And here comes the end of the third and last episode of our ice age lesson series.
In this article, we addressed two animals that lived during the ice age, the smilodon and the ground sloth or Diego and Sid from the Ice Age films.
We learned that the smilodon was a large prehistoric sabre-tooth cat that appeared on Earth around 2.5 million years ago and lived in North and South America. Despite looking similar to modern-day big cats, the smilodon was not related to them.
We also learned that smilodons thrived on Earth for so long before they went extinct around 10,000 years ago. And the reasons for that are still not sure.
Then we moved to the ground sloth, the current tree sloth’s prehistoric relative. The ground sloth lived on Earth some 35 million years ago and first appeared in North America. Then it dispersed to Central and South America.
Ground sloths are among the most diverse animals, for there were over 100 species of them, divided into over 80 genera and belonging to six different families. Ground sloths are thought to have disappeared around 10,000 years ago.
We hope you liked this lesson as much as we loved writing it for you. If you have not yet read our first two ice age episodes, you can find them here and here.
And until another adventure, keep learning.