Ancient fish is half a meter long

The flat-headed, half-meter-long fish survive in the ocean of 92 million years ago by eating plankton.

The researchers say they have identified two new forms of Rhinconichthys , which feed on plankton living in the Cretaceous period, the period when the dinosaurs dominated the ground. This is a fish with a length of more than 1.8m, a large head and wide gap between the jaws. Fate with the same creatures, Rhinconichthys became extinct after the meteorite disaster hit the Mexican Yucatan Peninsula, 66 million years ago.

Before the study was published, scientists knew a species of Rhinconichthys. The new discovery raises the total number of species to 3 and demonstrates that this ancient marine organism is distributed almost all over the world, the team concluded.

Fossil specimens of fish have a large head that helps scientists understand more about the distribution of this creature in ancient times.(Photo: Robert Nicholls).

"Based on the new study, we now know three different Rhinconichthys species, living in three distinct regions on Earth, each represented by a fossil skull," co-author Kenshu Shimada, Paleontologist at DePaul University, Chicago, USA said. "This shows the meagerness of the information that people have gathered about biodiversity across the history of the Earth."

Shimada first saw the fossil Rhinconichthys 30 years ago in the office of teacher Teruya Uyeno, who once held the position of managing the National Museum of Natural Science and Japan.

Then, in 2010, he and his colleagues excavated the fossil of a Rhinconichthys in England, named R.taylori. "At that time, we didn't think that this creature was so diverse and distributed throughout the Earth," Shimada said.

In 2012, the team discovered another fossil specimen in southeastern Colorado, USA. The fossil is called R.purgatoirensis , placed in the valley of the Purgatoire river where it was found. The excavation team then took more than 150 hours to move the whole specimen out of the surrounding rock.

Fossils of Rhinconichthys species in different areas on Earth.(Photo: K.Shimada).

In the study published in Cretaceous Research on January 28, scientists describe Colorado specimens and fossil re-analysis was discovered previously in Hokkaido, Japan called R.uyenoi (after Teruya Uyeno). From here, they have the basis to better understand the life of the ancient ocean.

According to Livescience, Rhinconichthys is part of the Pachycormids family , which includes the largest fish known to be on the planet. The Pachycormids are extinct and there are no descendants today, but in their heyday, they existed in large sizes. For example, all known Rhinconichthys species have up to two meters long, nearly two meters long, with a large head occupying 0.5 meters.

Rhinconichthys also possesses a terrible mouth with large gaps in his jaws, which looks like Muppet puppet character, Shimada researcher described. The bones called hyomadibulae form seven paddle shapes, making the jaws expand, allowing them to fill the mouth of plankton in the sea.

"The true pachycormids have" swept away "all the fleets in the ocean with industrial consumption , " Shimada said. "The fish has a wide mouth like a 0.3 meter diameter tube, sucking in a large amount of seawater and filtering out plankton thanks to its large bearing."

Rhinconichthys species are characterized by a wide mouth, the gap between the two large jaws is like the Muppet tangled character.(Photo: K. Shimada).

The ephemeral menu , or "planktivorous" today, is still used by many marine vertebrates, such as blue whales, rays or whale sharks. Thanks to the discoveries of Rhinconichthys, the researchers knew that this feeding method had existed during the Mesozoic period, when dinosaurs still existed.

"The human knowledge is just like a few small scratches on the vast surface of the complex ecosystem under the ocean in the era of dinosaurs at the time," Shimada said.