To many people, most of the frogs in the world are cute with big watery eyes, round bellies and soft bodies. Although a large proportion of the world's frog species are poisonous, most of them are docile and non-aggressive.

When biologists studied frog skulls, however, they found that they were downright debauched on the evolutionary trail. Contrasting the frog's docile appearance, the biologists thought it was all too crazy? Underneath the frog's smooth skin, many species may have delicate or hard crown-shaped skulls, false fangs, real fangs and even poisonous spines.

Researchers from the Florida Museum of Natural History used 3-D data to study the shape of the skulls of 158 frog species, which represent all extant frog families. The skulls of most frogs are rhizomatous but covered with a variety of complex grooves, ridges, and pits formed by additional layers of bone. The team found that this trait, known as

hyperostosis

, has evolved more than 25 times in frogs. Species with the same diet or defenses tend to develop skulls with similar shapes and patterns, even if they have evolved apart over millions of years.

Daniel Paluh, lead author of the research paper and a doctoral student at the University of Florida, said that the skulls of the frogs are not the same as those of the frogs. Daniel Paluh, said: ? On the surface, the frogs look similar, but when you look at their skulls, you realize there are huge differences between them. Some of the strangest skulls are found in frogs, some eat birds and mammals, others use their heads as shields, and the skulls of a few species of frogs are even poisonous.?

The last comprehensive study of frog skulls was published in 1973. Since then, scientists have doubled the number of frog species described, updated our understanding of their evolutionary relationships, and developed new analytical techniques with the help of CT scans. This has allowed Paru to use 36 markers on the frog's skull, scan and digitize them, and finally analyze and compare the shape of the frog's tree of life.

Paru found that not only do over-osteodermization and strange skull shapes tend to go together, but that they are usually associated with the frog's habits? Frogs either eat very large prey or use their heads for defense.

Frogs that typically eat birds, reptiles, other frogs and mice have huge, spacious skulls with jaw joints near the back. This gives them a larger open mouth for grasping prey, as is the case with Parman frogs, Paru said. His analysis shows that the skulls of these species are covered with tiny pits that provide extra strength and bite.

Almost all frogs do not have teeth in their jaws, but some, such as the Buggy Frog, have evolved lower, fang-like structures that allow them to inflict stabbing wounds on prey. One species of marsupial frog, called the Guenther, has real teeth in both jaws and can eat prey up to half its own weight.

Some frogs block the entrances to their burrows with their heads to prevent them from being eaten by predators. These species of frogs tend to have spongy skulls covered with small spines. Some, like Bruno's black-headed frog, have recently been found to be poisonous. When a predator pounds the head of these frogs, the specialized spines pierce the poison glands under the skin as a defense.

While the study shows a persistent overlap between excessive ossification and odd skull shapes, the researchers aren't sure which started first. Did frogs start eating large prey first and then evolve stronger skulls, or was it the other way around? Paru says it's a ? question of whether the chicken or the egg came first?

More than 7,000 species of frogs have been discovered today without the strengthened skulls of their *** same ancestors. But herpetological research co-author David? David Blackburn, co-author of the herpetology study, says

The ancestors of the frogs' ancestors emerged with strengthened skulls

. While none of the frog's ancestors had an overly ossified skull, the skulls of fairly ancient amphibian ancestors showed enhanced features. Ancient genes may be manipulating this madness.

Previous studies have proposed that frogs evolved the over-osteodermic trait to protect against water loss in arid environments, but Paru's research found that habitat and over-osteodermization are not necessarily absolutely causally linked. The trait has been found in frogs that live underground, in trees, in water and on land.

But habitat does affect the shape of the skull: aquatic frogs tend to have long, flat skulls, while frogs that specialize in digging usually have short, pointed skulls, a shape that also allows them to use their mouths like chopsticks to catch small, fast-moving prey such as ants and termites, Paru said.

The survival of the fittest. Relatively speaking, the weaker the species in nature, the more frantic and diverse the evolution, because the only way they can keep from being eliminated by nature is to change. The world all this is not so? Change in order to move forward.