Skulls of ancient lungfish told about the evolution of the brain of vertebrates

(ORDO NEWS) — An international team of researchers scanned the skulls of extinct and living lungfish, the closest relatives of tetrapods. Scientists were able to guess what their brain looked like.

It turned out, unlike all other fish, lungfish relied on the sense of smell more than sight. The results of the study will allow a better understanding of what the brain of the first land animals looked like.

An international team of scientists led by researchers from Flinders University (Australia) compared detailed 3D skull models of six fossil and two modern lungfish species.

The results of the study, published in the journal eLife, help to better understand the evolution of the brain of lungfish, which in turn can be useful in describing the very first four-legged animals.

Lungfish are an ancient group of freshwater bony fish that have both gill and pulmonary respiration. They appeared in the Devonian period and have survived to this day. These fish are the closest relatives of tetrapods, so their research can reveal a lot about evolutionary history.

Scientists focused on the nervous system of ancient lungfish. Soft tissues are poorly preserved in the fossil record, but the skull can tell a lot about the structure of the brain.

The authors used X-ray tomography to study the endocranes of six Paleozoic lungfish fossils found in Australia, the United States and Germany, and two modern representatives of this group. Endokran is a relief of the inner side of the skull, allowing you to draw some conclusions about the structure of the animal’s brain.

The brains of lungfish have evolved throughout their 400-million-year history, the study found. At the same time, the olfactory region turned out to be the most variable. In some species, they have undergone significant elongation.

Lungfish relied much more on sense of smell than sight when navigating their environment, which made them very different from all other fish. Probably, this may be due to a change in habitat. Lung-breathing fish do not prefer the water column, but shallow coastal waters.

Understanding how the lungfish brains have changed over the course of their evolutionary history helps us understand what the brains of the first tetrapods that landed about 350 million years ago might have looked like, as well as what sense organs played a major role in their lives.

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