This "Grinning Crocodile" is Possibly the Answer to Evolution

A 372 million-year-old fossil found in Russia is said to be that of a weird-looking creature.

This creature is a tetrapod, or fish species that evolved to become a land-dweller, and is given the name Parmastega aelidae. Compared to the current era's animals, this one looks a  like a cousin of crocodile, except it has a pair of uses sticking out on top of its head. Its nose and jaws also shaped as if the species is grinning.

What is Tetrapod?

(Photo : Berkeley.edu)
Although it means "four feet" in Greek, Tetrapods are all land-dwelling animals, including birds, limbless reptiles like snakes, and animals that return to water like turtle and seals.

Tetrapods, which means "four -legged" in Greek, are all land-dwelling vertebrates, including animals who return to sea like turtles and seals.

According to scientists, the earliest tetrapods known are fishes that became common ancestors of animals above the water like reptiles, birds, amphibians, and mammals. They evolved around the Devonian period, or the "Age of Fishes" which happened at least 416 million to 358 million years ago. 

Before the discovery of Parmastega aelidae, scientists believed that the oldest tetrapods lived about 390 million years, based on the carbon dating result of fossilized footprints.

Discovery of the early tetrapods

The "grinning crocodile" tetrapods were discovered in limestone deposits that used to be a lagoon located in Sosnogorsk, Russia. Based on the study published on Wednesday in the journal Nature, these fossils were able to maintain some fishbone characteristics.

According to the scientist, its nose and jaws were submerged underwater, and it has sensory organs in its skull to sense vibrations in the water. It is also breathing through grills that are possibly more than three feet long.

Modern-day crocodiles also have similar hunting mechanism. But based on the analysis of the fossils, these tetrapods possibly never left the water because its shoulder girdle and limbs are possibly made from cartilage, making walking outside the water difficult. Scientists suspect that they grabbed their prey on the shoreline.

Nodla Fröbish and Florian Witzman from Natural History Museum in Berlin, who are not involved in the study, said that among the modern animals, mudskippers are probably the closest to these tetrapods. Yet mudskippers use their eyes to watch out for land or avian predators, which do not exist yet in that era.

Other features of the tetrapods include sharp fangs on the upper jaws and needle-like teeth on the bottom one.

The mystery of these tetrapods

The researchers called the origin of these tetrapods a "tangled bush of ecological experimentation" since they are still far from presenting the progression of ancient water animals to land-dwellers.

Fröbish and Witzman compared the development of tetrapods to a "plot of a crime novel".

The P. aelidae fossils offer a lot of information that might help in understanding the complexity of evolution, and the discovery of the fossils is a reminder that there is still more to learn, the duo also said.