There are around 4,740 known species of frog around the world. The number is in constant flux because many species are going extinct while new species are being discovered. But what remains consistent is the staggering level of diversity among frogs and toads. These amphibious creatures have evolved to specialize in their unique habitats in ways even the most creative fiction writers couldn't have dreamed up. From frogs that make squeaker-toy sounds to frogs that fly to frogs that give birth out of their backs, we have some doozies to share with you!

Diane's bare-hearted glass frog

bare-hearted glass frog

This newly discovered species quickly rose to fame thanks to its similarities to Kermit the Frog. (Photo: Costa Rican Amphibian Research Center)

This little frog recently made the headlines thanks to its resemblance to a celebrity: Kermit the Frog. It also made headlines because it's a newly discovered species.

We reported earlier this month, "Minnesota researcher Brian Kubicki, creator of the Costa Rican Amphibian Research Center, found the Kermit the Frog wannabe in the Caribbean slopes of Costa Rica. According to the official announcement on the center's website, this particular glass frog is unique due to its coloring, the sound of its call, and other morphological features — including its Kermit-like eyes. Kubicki said the small, semi-translucent frog 'is a good indicator of the general health of the ecosystem.'"

And just to ramp up the aww-factor a bit more, he named the new species after his mom.

This miniscule frog is only about 1 inch long, and it's a species of glass frog. Glass frogs are called such because the skin on their bellies is so translucent, you can see their organs.

Paedophryne amauensis

Tiny frog sits on a coin

Smaller than a dime, this tiny frog species is the world's smallest vertebrate. (Photo: Rittmeyer EN, Allison A, Gründler MC, Thompson DK, Austin CC/Wikipedia)

The Diana's bare-hearted glass frog may be tiny but it has nothing on the Paedophryne amauensis, also a relatively new species to science as it was only discovered in August 2009.

This species grows to only 0.3 inches, making it the world's smallest vertebrate. For perspective, the coin it is sitting on is a dime.

Not only is it tiny but its calls are similar to those of insects, plus their coloring matches the leaf litter on the forest floor. No wonder it took scientists awhile to notice it! The strategy used by the two researchers who discovered it were to use triangulation to determine the location of the call, then scoop leaf litter into a plastic bag to figure out what was making the noise. Then there it was, the tiniest frog in the world. Paedophryne amauensis is found in Papua New Guinea.

Desert rain frog

This unusual species is like a cartoon come to life — or a squeaker toy.

Found in Namibia and South Africa along a 6.2-mile wide strip of coastal habitat, the species is found in subtropical or tropical dry shrubland or coastal sand. It buries itself in 4-8 inches of sand during the day where it can stay cool and moist, then comes out at night (especially on foggy nights) to feed on insects and larvae.

After this video by Dean Boshoff was posted online, it also became the unofficial world's cutest frog.

Ornate horned frog

ornate horned frog or Argentine horned frog

This species is sometimes called a Pacman frog because of its exceptionally large mouth. (Photo:/Shutterstock)

While some frogs choose to hide, others choose to stand out. Such is the ornate horned frog, also known as the Argentine horned frog, Argentine wide-mouthed frog, and ornate Pacman frog.

Why "Pacman" frog? Because this frog will try to swallow pretty much anything that gets close to its unusually large mouth. The frog's menu includes everything from insects to rodents to other frogs. It has an insatiable appetite packaged in a 6-inch body that is half mouth — literally. Its mouth accounts for around half of the frog's body. As the National Zoo puts it, "These frogs are sometimes called 'mouths with legs' because the mouth appears to be the entire front half of the body."

Wide-mouthed indeed! Their bite is, as you might expect, powerful. You don't want to get your fingers anywhere near these guys!

Hairy frog

hairy frog or Trichobatrachus robustus

With growths like sideburns and claws that suddenly sprout from its toes, it's no wonder this species is sometimes called the Wolverine frog. (Photo: Gustavocarra/Wikipedia)

Trichobatrachus robustus is, frankly, a bit on the creepy side. The species is also known as the horror frog or Wolverine frog, in part because if threatened, it will intentionally break its own toe bones, which then stick out through the skin to act like claws. These bones later retract on their own and the damaged tissue heals. It's the only animal researchers know of with such a defense mechanism.

The name of the Wolverine frog is fitting not only for the bony "claws" that come flying out of its feet but also for the hair-like growths on the sides of the males called dermal papillae. Breeding males grow the papillae, which have arteries and are believed to help increase the surface area of the frog so it can absorb more oxygen as it stays underwater for long periods of time guarding eggs laid by females.

The species is found in central Africa and, while not considered endangered, is threatened by habitat loss.

Vietnamese mossy frog

Vietnamese mossy frog

This frog's rough green skin perfectly matches its mossy surroundings. (Photo: davemhuntphotography/Shutterstock)

This species ranks way up there among the froggy masters of camouflage. Living in subtropical and tropical lowland forests, as well as freshwater marshes, its skin mimics the look of moss, turning it into what looks like a moss-covered rock when the frog sits still. Even its eyes have the same textured appearance through their coloration.

You can see how much these creatures look like the surrounding moss in the photo below:

mossy frog

It's easy to see why the mossy frog was so named. (Photo: davemhuntphotography/Shutterstock)

The species takes that rock-like appearance to an extreme by rolling up into a tight ball when threatened, trying with all its might to look like any other rock in the area.

These frogs grow to be between 2.5-3.5 inches long, and they have an adhesive disk at the end of each toe that helps them easily scale rocks and trees.

Golden poison dart frog

Golden poison dart frog

This tiny, vividly gold frog is one of the most toxic creatures in the world. (Photo: /Shutterstock)

The scientific name for this species is Phyllobates terribilis, and for good reason. As one of the most toxic animals on the planet, a single 2-inch frog has enough toxin to kill between 10-20 adult humans, or two bull elephants. Just one gram of the toxin produced by the skin of the the golden dart frog could kill 15,000 people.

Just how the tiny frogs manage to be so toxic is still a mystery to researchers, but it's believed they get it from the poisonous plants eaten by their prey of insects, beetles, ants and termites. Frogs raised in captivity never become toxic; only the wild frogs are lethal. Their skin is coated in alkaloid toxin, which can persist for a long time after the frogs have been separated from their usual food sources.

As for being food itself, the frog kills everything that tries to eat it, except for the snake species Liophis epinephelus. This is the only species known to have a resistance to (but not immunity from) the toxin of the golden dart frog.

There are around 100 species of poison dart frogs, but Phyllobates terribilis is among the largest. National Geographic writes, "They live within a tiny plot of rain forest on the Pacific coast of Colombia. And though the population in its small range is abundant, widespread decimation of the rain forest has landed this species on international endangered lists."

Indian bullfrog

Not all yellow frogs will kill you. Some will just entertain you with their singing skills. The Indian bullfrog is a vividly colored species found in south and southeast Asia.

For most of the year, these frogs are a dull olive green color. However, during mating season, the males turn a day-glo yellow with indigo vocal sacs on their throats, all the better to attract the attention of potential mates.

With a body about six inches long, this is the largest of the Indian frog species. In the 1990s, people started farming the frogs as a food source. They have also become an invasive introduced species in Madagascar.

Brazilian horned frog

Brazilian horned frog

This aggressive frog matches its surroundings, making it a deadly foe for any passing prey. (Photo: Dirk Ercken/Shutterstock)

The Brazilian horned frog has a mouth as huge as the ornate horned frog and a reputation for being just as aggressive, if not more so. Blending into the leaf litter on the forest floor, the 8-inch long frog only has its (huge) head visible, ready to snatch any potential prey that wanders past. Some specimens have been found dead with prey sticking out of their mouths, having suffocated rather than give up a large meal.

It will go after practically anything, including intruders, and that includes the feet of people walking past. So the word of advice around this frog is don't tread too near one!

Wallace's flying frog

Wallace's flying frog

Flying frogs use their feet as miniature parachutes to glide from one place to another. (Photo: Ryan M. Bolton/Shutterstock)

Some frog species do more than hop. They fly — or at least glide anyway. There are several species of "flying frog" and the Wallace's flying frog is one of them. These frogs have especially long toes with a great deal of webbing between them, allowing them to spread out to become four tiny parachutes. They also have flaps of skin on their front limbs for extra help.

Wallace's flying frogs live almost entirely in trees and come to the ground only to mate and lay eggs. They use their "flying" ability when threatened, leaping from a branch and spreading out their feet to glide as far as 50 feet in a single bound toward safety. Though not the only species with this capability, they are one of the largest, though that isn't saying much. They grow to only about 4 inches long.

The future of the frogs may be somewhat tied to the future of Asian rhinos. According to National Geographic, "[T]hey are partial to breeding and laying eggs in the fetid wallowing holes of the nearly extinct Asian rhinoceros, and further decreases in rhino populations may negatively affect the species."

flying frog

This 4-inch frog can glide as far as 50 feet in a single leap. (Photo: Norhayati/Shutterstock)

Venezuela pebble toad

The pebble toad is the perfect name for this little amphibian because of its defense mechanism. The pebble toad lives on steep slopes and isn't a powerful jumper, so, when it's threatened, it tightens its muscles to become rigid and tumbles down the hill to safety. Because it's so light, bouncing along the cliff face doesn't harm the little toad. It lands uninjured in puddles or crevices. The strategy provides a quick escape from predators like tarantulas.

Not only does it act like a pebble rolling down a hill, but it tries hard to look like one too. The murky coloring of the inch-long toad is intended to help it blend in with its rocky surroundings, and when curled up like a ball, it looks just like a tiny rock.

Suriname toad

pipa pipa or Surinam toad

Though it looks like road kill, this flattened frog is actually alive and well. It is possibly the flattest frog around! (Photo: Hugo Claessen/Wikipedia)

Also known as the pipa pipa, this may be one of the most bizarre frog species out there, with a disconcerting (or simply disgusting) way of reproducing.

But first, let's talk about that unique shape. The Suriname toad is almost completely flat, with miniscule eyes, no tongue and no teeth. Instead of croaking, it taps two bones in its throat to make a high-pitched, sharp click noise.

Weird, right? But it gets weirder.

Suriname toads reproduce underwater. During mating, the female releases batches of three to 10 eggs at a time, which land and become embedded into her back. Sinking into the skin, the eggs are held all the way through the tadpole stage in their little pockets, and finally emerge as fully developed toads. Yes, fully developed tiny toads are tossed from her back in spasms. It's incredibly strange, somewhat disturbing, and yet a must-watch:

Purple frog

purple frog

This species lives underground for the entire year except during a two-week mating period. (Photo: Karthickbala/Wikipedia)

This bizarre looking creature is difficult to recognize as a frog right away due to its, well, blob shape. It is found in the Western Ghats mountain range in India, and its closest relatives are in the Seychelles, off the eastern coast of Africa. This species has evolved independently for over 120 million years, which explains its unique appearance. It's also sometimes called the pignose frog, due to it's long-ish snout.

The shape, and indeed the purple coloring, is understandable because it lives the majority of its life underground eating termites. The purple frog surfaces only for two weeks out of the year during the monsoon season, during which it mates and then heads back underground.

It's this underground life that kept it away from the eyes of scientists for so long. It was only formally described in 2003.

Malagasy rainbow frog

Malagasy rainbow frog

Vividly colored, this frog is popular in the pet trade. Unfortunately that also has been a factor in causing it to become and endangered species. (Photo: Franco Andreone/ Wikipedia)

This frog species from Madagascar goes by many names, including the ornate hopper, the rainbow burrowing frog, the red rain frog or the Gottlebe's narrow-mouthed frog. This frog, by any name, is just as colorful. The species is known for its vibrant patterns of red, orange, green, black and white.

Not only is it colorful but it's a skilled climber. By day, the frogs burrow in sandy areas next to streams. By night, they climb the surrounding rocky areas, sometimes climbing vertical walls thanks to the sharp claws on its front feet that help it to grip. It is one of the few frogs that are built to be good at both burrowing and climbing.

The species is endangered in large part because thousands are collected from the wild every year for the pet trade.

Malayan horned frog

Malayan Horned Frog

The fleshy 'horns' are all part of this species' camouflage strategy to look more like a leaf. (Photo: Ryan M. Bolton / Shutterstock)

This devilish frog is designed to look like leaves on the forest floor, complete with horn-like projections atop its eyes and nose to add to the spiky look of leaf edges. It lives in the leaf litter of damp, cool lowland rain forests in southeast Asia, so it needs to blend in with the other leaves to stay hidden from both predators and prey. It would be difficult to pick this frog out from fallen leaves when walking by:

Megophrys nasuta or Malayan horned frog

See the horns on the Malayan horned frog? (Photo: kurt_G/Shutterstock)

The Malayan horned frog waits motionless until prey passes close by, then it rapidly strikes. The usual prey for this species, though, is insects. It also eats spiders, lizards, other frogs and even small rodents.

Everything from the mottled coloring to the skin folds running along its sides and back make it look just like leaves. But from the side, this creature can look almost bat-like.

Malayan Horned Frog

You can see how the Malayn horned frog looks like leaves. (Photo: Eric Isselee/Shutterstock)

Jaymi Heimbuch ( @jaymiheimbuch ) focuses on wildlife conservation and animal news from her home base in San Francisco.