The horned gopher:

Show transcript:

Welcome to Strange Animals Podcast. I’m your host, Kate Shaw.

This time we’re going to learn about some mammals with weird horns. Specifically, weird nose horns. Nose horns are properly called rostral horns, but that’s not as funny.

We’ll start with a family of extinct rodents called horned gophers, or more properly, mylagaulids. The horned gopher wasn’t a gopher, but it probably looked similar to ground squirrels like prairie dogs and marmots. It lived in what is now North America around twenty million years ago, and it had a pair of short, broad horns that pointed upwards between the nose and eyes, like a rhino’s horns but side by side and made of bone, not keratin. It was big for a rodent, about a foot long, or 30 cm, and ate plants.

So what did the horned gopher use its horns for? Both males and females had the horns and they’re too short and placed too far back for males to use them to fight each other. Horned gophers had poor eyesight so males probably weren’t trying to look and act flashy to attract females anyway.

At first researchers thought the horns helped in digging burrows. The horned gopher primarily used what’s called the head-lift method of digging, which means it pushed its nose into the dirt, then lifted its head with powerful neck muscles to remove a chunk of soil—basically using its nose as a shovel. But its horns pointed straight up and were set too far back on the nose to help with digging. Most researchers today think the horns were used for defense. If a predator tried to grab the animal by the neck, it could snap its head back and stab the predator right in the face.

The horned gopher had tiny eyes and front feet that resembled a mole’s, with long claws. Researchers think its ancestors probably spent most of the time underground, but that as it evolved to become larger, it also spent more time foraging above-ground. That led to more predators being able to attack it, so evolving horns as a defensive weapon helped it survive.

While the horned gopher was distantly related to modern squirrels, its family is completely extinct these days. But it’s still the smallest known horned mammal that ever lived.

The horned gopher is also the only horned mammal known that lived mostly underground in burrows. Almost. There was once a type of armadillo, naturally called the horned armadillo but more properly referred to as Peltephilus [pelta-FEElus], that had a pair of horns over its eyes but a little in front of them, close to where the horned gopher’s horns were. The horned armadillo’s horns developed from scutes on its head, and if you remember, scutes are bony plates embedded in the skin as armor. It might also have had a smaller pair of horns over its nostrils. It lived in what is now South America and went extinct around 11 million years ago.

The horned armadillo dug burrows liked the horned gopher did, but it was much bigger than the horned gopher, with some species as much as five feet long, or 1.5 meters. Despite its size, it probably resembled the pink fairy armadillo in overall shape rather than the more common nine-banded armadillo that lives in parts of North America. It had a short tail and its rump was squared off instead of rounded. It also had big sharp teeth. It may have eaten insects, possibly digging up ant nests, but more likely it mostly ate roots and other plant parts.

Arsinoitherium was another animal with nose horns, this one from Africa. It lived around 30 million years ago and was related to modern-day elephants, but it lived in swampy areas and tropical rainforests and ate plants. It probably looked a little like a rhinoceros and a little like a small elephant without a trunk. Different species were different sizes, but they were all pretty big, probably no smaller than about six feet tall at the shoulder, or 1.75 meters. And they had two pairs of horns, a little pair more like bumps over the eyes and two side-by-side forward-pointing giant nose horns that looked a lot like rhino horns but thicker. But they were real horns made of bone, not keratin, although they may have been covered in skin and hair like ossicones. You know, ossicones are those hornlike structures giraffes have.

Brontotherium looked a lot like a rhinoceros too, but that’s because it was distantly related to the rhino, although it was more closely related to the horse. It lived in North America around 35 million years ago and was enormous, standing around 8 feet tall at the shoulder, or 2.5 meters. It was a selective browser, probably preferring tender leaves to tough grass. It carried its massive head low like modern rhinos and buffalo do, and had a humped shoulder like both those animals where its massive neck muscles attached. And it had a pair of nose horns.

Both males and females had the nose horns, but the males’ horns were much larger. The horns were blunt and shaped sort of like a V, and researchers are pretty sure males used them to fight each other. We have fossilized brontotherium rib bones that show an injury shaped just like the nose horns. The horns were probably also useful to fight predators. Even though brontotherium was related to the rhino, its horns were bone, not keratin.

Our last nose horn animal lived in North America up to about five million years ago. The various species of Protoceratidae [pro-TOSS-e-rated-die] were hoofed animals that looked sort of like deer, but were more closely related to a living ungulate called the chevrotain, or mouse deer. Protoceratid probably ate grass and other plants and may have lived in herds. Males had a pair of ordinary horns that looked a lot like cow horns, and in some species females had the horns too, although they were smaller. But males also had a horn on the nose. And it was weird.

Once again, the nose horn wasn’t like a rhino’s horn, which as we have established by now is made of keratin. And maybe I should have reminded you before now that keratin is the same protein that makes hair, fingernails, hooves, and things like that. Keratin also doesn’t fossilize. This nose horn was an actual horn made of bone, but researchers think it may have been covered with skin and fur like an ossicone.

Different Protoceratidae had different nose horns. Syndyoceras had a pair of nose horns that were fused at the base, then split apart to form a V shape. It may also have had large nasal passages that made its muzzle look much bigger than the skull would suggest at first glance. Synthetoceras had a long nose horn that grew up and slightly forward but split into a Y at the tip. Kyptoceras had a pair of nose horns that pointed forward. Researchers think the males used these nose horns to fight each other, much like deer fight with their antlers today.

One older Protoceratid that lived up to around 20 million years ago was called Protoceras, and males had three pairs of horns, although they probably resembled ossicones and were all covered in skin and hair. A small pair grew between the ears, another pair between the eyes and nose, and the largest pair grew on the nose. Females only had one smaller pair of horns between the ears, so the extra horns males had were probably for display.

Some Protoceratidae also had a pair of fanglike canine teeth that they may have used to root around in dead leaves for plant material. Male chevrotains have fangs like this too, but they use them to fight each other since they don’t have horns.

So basically, this is what we’ve learned from this episode: There used to be a lot more nose-horned animals than we have now, most of them lived in the Americas for some reason, and they were all awesome. Also, even though the first animal we think of when someone mentions nose horns is the rhino, the rhino’s keratin horns are actually unusual. Just be glad you’re not an intelligent birdlike creature from the far future trying to figure out what a rhinoceros actually looked like when it was alive.

Thanks for your support, and thanks for listening!

Episode 483: Animals with Nose Horns