Have you ever looked at a frog chowing down on a meal and wondered if that frog has teeth? Has it progressed to questioning if frogs, in general, have teeth? Of course, it has. It turns out carnivorous frogs, which make up most of the group, DO have teeth. However, if you’re envisioning a dental arcade similar to mammals or even reptiles, you’re in for a surprise.
Some Frogs Have Teeth
Carnivorous frogs have two kinds of teeth: maxillary and vomerine. They differ from mammalian teeth in a few ways. First, frogs only have teeth in the maxilla, or upper jaw. (Hold your breath, though, because there’s a revolution coming) The mandible (lower jaw) lost its teeth about 250 million years ago. (Remember that number)
Second, where mammals only lose one set of teeth throughout their lives, frogs continuously replace their teeth. There’s always a “functional” tooth in place with a replacement waiting in the wings at every position. (Good thing frogs don’t have Tooth Fairies)
Third, frog teeth are conical in shape. Kind of nerve-wracking, but, for the most part, you don’t need to worry. Frogs don’t rely on those teeth for defense. However, there are exceptions to every rule, and the African bullfrog is that exception.
Commonly referred to in the pet trade as Pac-Man Frogs, these bullfrogs reach large sizes in the wild. As such, their prey tends to be larger, too: mice, lizards, and other frogs. The bullfrog’s teeth are large and sharp, referred to as odontoid processes or odontoids. They also have sharp, recurved maxillary teeth. When threatened (such as when lifted by nosey humans), they are known to bite. Odds are you won’t lose a finger, but you’ll yield some blood. As with any animal, it’s best to show respect when handling even your pet frog.
A frog’s maxillary teeth aren’t visible from the outside. Even when a frog open’s their mouth, it can be tricky to spot this row of tiny teeth. (Seriously, put that poor frog down) The little cones line the edge of the mouth. The maxillary teeth are pretty much identical in size and shape. Unlike mammals, frog teeth don’t specialize. Why? Maxillary teeth just have one function: food assistance.
No, frogs are not chewing. That conical shape doesn’t function well for chewing. It DOES help hold and maneuvers the frog’s prey down their gullet, though. Frogs use their arms, tongue, and eyes to force the prey item down their throats. Wait, eyes? True story: frogs retract their eyes into their head, creating pressure within the oral cavity. The prey in their mouth then slides backward.
So why the need for those maxillary teeth? Frog tongues aren’t anchored to the back of the mouth as mammal tongues are. Frog tongues attach at the front. Great for catching prey, not the best for prey manipulation. The teeth hold food steady while the frog swallows. They also help shift the prey back toward the throat.
If you thought the maxillary teeth were difficult to see, forget trying to find the vomerine teeth. Vomerine teeth get their name from their position in the vomer bone of the skull. (This is part of the nasal region) They tend to be pointy and are found in tiny clusters of two. A mucus membrane partially obscures them from view. (Which is why you need to put that frog down – you’re wasting your time)
Once again, the function of the vomerine teeth is in food assist. Along with the maxillary teeth, they keep prey items in place while the frog swallows. You find the vomerine teeth in the roof of the mouth, where they provide a solid anchor for the frog’s meals. The sharp points dig into the prey’s body. It’s not a bite, but the prey doesn’t exactly feel a massage, either.
Toads Don’t Have Teeth
Frogs and toads share many similarities, but it’s a simple task to differentiate the two. It turns out their mouths provide another divergence. Toads just don’t have teeth. As toads are primarily ambush hunters, they rely on their skills of camouflage to enable them to stalk their prey. Stunning an insect (or mouse) gives them enough time to swallow the prey item whole – no need for maxillary or vomerine teeth to aid in the process.
However, before you feel a need to prod your next garden invader in the mouth, consider the fact that they’re IN your garden first. Unless they’re taking a swim in the pond, the odds are you have a toad settling in among the flowers. (And, really, the bumpy skin should give them away in the first place)
Remember that 250 million-year-old frog ancestor that abandoned mandibular teeth? Dollo’s Law states that, since the evolutionary trait went out the window, it SHOULD be lost forever. It’s why humans no longer have tails. The species decided we didn’t need them, so evolution scrubbed the genes from the pool. Or so the theory goes.
At least until Gastrotheca guentheri, Gunther’s marsupial frog, showed up and threw gasoline on the evolutionary fire. Why? These little frogs – named for the egg pouches the females carry on their backs – have mandibular teeth. So far as anyone knows, they’re the only species that have those teeth. What shocked everyone is the mandibular teeth appeared in the fossil record 20 million years ago. This line of marsupial frogs RE-EVOLVED a lost trait.
While Gunther’s marsupial frog could care less about its shocking impact on evolution, the appearance of a lost trait is big news. If this species of marsupial frog can develop mandibular teeth, what’s to stop other species from regaining their lost teeth?
After all, every carnivorous species of frog already has the building blocks. (Mandibular teeth are similar to maxillary teeth: conical in shape and used to manipulate prey) The same calcium exists in every frog’s body, and the structures are the same. Why couldn’t other species decide to bring back mandibular teeth?
This revelation doesn’t stop with frogs, either. Maybe other species could retain “lost” traits, assuming environmental conditions presented themselves. (And, naturally, assuming the basic building blocks for the feature exist in the species) It gets the minds of evolutionary biologists churning.
Whether you’re interested in the evolutionary perspective or just satisfying general curiosity, looking into frogs and their teeth open the mind.
No, the frogs in the pond won’t munch on your fingers anytime soon, but they will munch on the dragonflies. Even if you can’t see the teeth in action, you can still appreciate knowing they’re there.