Animals and Ancestors Part 3

Q: Which Modern Animals Had Ancient Ancestors? A: All of them! 

Welcome again to another installment of “Animals and their Ancestors”! It’s been far too long since we took a look at modern day animals and some of their perhaps not-so-obvious relatives from long, long ago. So, without further ado, let’s dive right in! And if you'd like to check out the first two installments in this series, you'll find them here (Part 1) and here (Part 2).

What Were Crocodile Ancestors Like?

We begin, as we have in the past, with crocodiles. As you might expect if you’ve read our last two “AATA” blogs (we’re abbreviating it now, it’s just easier that way), the ancient relatives of crocodiles and alligators were strange and varied, and in some cases not very croc-like at all. Take Prestosuchus, for example. This large extinct reptile was discovered in 1942, but new studies from as recent as 2013 have shed even more light on this prehistoric beast.

The leg muscles of a well-preserved specimen showed that Prestosuchus shared many muscle groups with both birds and crocodiles, indicating a link between these two animal groupings. Crocodilians and birds are the last surviving members of the archosaurs, a group that also included the flying pterosaurs and all non-bird dinosaurs. Despite being quite dinosaur-like, with its mostly upright posture, Prestosuchus was part of the lineage that would one day lead to today’s crocs and gators.

Were Brontotheres Related to Rhinos?

Let’s move on now to mammals. Take a look at Megacerops. This creature was a member of the brontothere group, which includes some of the earliest of the large mammals in the fossil record. Megacerops (which means “large horned face”) lived around 35 million years ago and could weigh over three tons. If you had to guess what modern day animal was related to this large mammal with the prominent nose horn, what would you choose? Probably a rhino, and that would be a perfectly reasonable guess, considering their similarities. 

However, you’d be incorrect. The brontotheres were actually part of the suborder known as Hippomorpha, which also includes horses. That’s right, the closest modern relative to this decidedly rhino-like prehistoric mammal is one of our most common domesticated beasts of burden: the horse. Or rather, the horse family Equidae, which today includes horses, donkeys and zebras. Though there are wild examples of the donkey and the zebra, all horses today are either domesticated, or descended from domestic animals. A domestic animal that reverts to its wild stage is known as “feral”. It was once believed that Przewalski’s horse was the only “true” wild horse to never have been domesticated, but recent genetic studies have revealed it to have had domestic ancestors.

What Were Ancient Rhinos Like? 

Megacerops might be closer to horses than rhinos, but that doesn’t mean rhinos don’t have their own really cool ancestors. The mammals that would become rhinos first diverged from the other hoofed mammals in the Eocene, around 50 million years ago. The first rhino species were quite small, but as they evolved, they grew larger and larger. While most rhinos today are nearly hairless, their ancestors were not so bald.

The woolly rhinoceros first appeared around 4 million years ago, and may have lived until as recently as 10,000 years ago. These prehistoric beasts were as large as today’s white rhinoceros, and could grow to be over six feet tall and 12 feet long! However, unlike the white rhino, the woolly rhinoceros lived up to its name and was covered in a thick coat of brown fur. Unlike today’s rhinos which live in Asia and Africa, the woolly rhino lived in the frigid tundra of what is now Northern Europe. Since these creatures died out so recently, they are occasionally discovered as frozen mummies, with skin and other features intact. They are also seen in cave paintings done by early humans.  

Today, the closest relative of the woolly rhino is thought to be the Sumatran rhinoceros. This critically endangered rhinoceros is the only living species that still retains a substantial amount of fur. Because of this, scientists believed it was the most closely related of the modern rhinos to its hairy ancestor, and recent genetic studies confirmed this. Despite sharing its furry coat with the woolly rhino, the Sumatran rhino is much smaller, and is the smallest living rhino species, rarely growing longer than ten feet. 

Were Mastodons Related to Elephants and Mammoths? 

And finally, what installment of AATA would be complete without a discussion of elephants and their ancestors? We’ve talked in the past about early elephant relatives like Amebelodon, and closer relations like the woolly mammoth, but there’s one prehistoric elephant-like animal we have yet to touch on: the mastodon. At first glance, mastodons appear very similar to woolly mammoths, so you might think they’re closely related to modern elephants.

Surprisingly, this is not the case. While mastodons are clearly members of the group Proboscidea, which includes mammoths and elephants, they are only distantly related to them. They have all the superficial features: a long trunk-like nose, a heavy body with four thick legs, and long curving tusks, but it is believed that the mastodon family separated from the other members of the group around 27 million years ago.

Mastodons had shorter legs and longer bodies than elephants and mammoths, and lower, longer heads as well. Their teeth were also very different. Still, while they are not directly related to modern elephants, we felt that they were an important offshoot of the main Proboscidean lineage, so it was important to give them a mention here.

We hope you've enjoyed traveling down these ancestral pathways with us! As always, stay tuned for more!