They marked the exact moment of evolution when mammals became warm-blooded creatures

A mammal releasing hot air on a frigid night, hinting that it is endothermic (warm-blooded) (Luzia Soares/Creative Commons)

Scientists have answered an age-old question about mammalian evolution through screening Anatomy of the ear of living and extinct mammals and their relatives To determine When warm-blooded arose, an essential trait for a successful pedigree.

Researchers said Wednesday that The small size of the structures of the inner ear called the semicircular canals Small fluid-filled tubes that help maintain balance. In the fossils of ancestral mammals, it was shown that warm-bloodedcalled endothermy, sThey appeared about 233 million years ago, during the Triassic period.

The first creatures to reach this achievement are called synapses MammalsThey are not officially classified as mammals – those that appeared about 30 million years later -, but they are They began to acquire traits associated with them.

endothermic It evolved at a time when important features of the mammalian body structure were being formed, Such as bristles and fur, gait-related changes in the spine, presence of a diaphragm and a mammalian-like jaw joint, and an auditory system.

“Heat is a characteristic of mammals, including humans. An almost constant rise in body temperature regulates all our actions and behaviors.” (Brad Penner)

Endothermic andIt is a characteristic of mammals, including humans. A nearly constant rise in body temperature regulates all our actions and behaviors, From eating to cognition, and from movement to the places we live in,” said the paleontologist Ricardo Araujo From Institute of Plasma and Nuclear Fusion at the University of Lisbon, Co-author of study Posted in temper nature.

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High metabolism of mammalian bodies Maintain internal temperature regardless of their environment. cold-blooded animals, Like lizards, they adopt strategies such as basking in the sun to keep warm.

endothermic in mammals It came at a very frenetic time in evolution, like dinosaurs and flying reptiles called pterosaurs -creatures that will for a long time dominate the ecosystems- They first appeared at that time.

Endothermy offered advantages

The lineage of mammals evolved from cold-blooded creatures, some of which had strange body structures, such as Dimetrodon, which mixed reptilian traits, such as flat legs, and mammalian traits, such as disposing of some jaw muscles (Reuters)
The lineage of mammals evolved from cold-blooded creatures, some of which had strange body structures, such as Dimetrodon, which mixed reptilian traits, such as flat legs, and mammalian traits, such as disposing of some jaw muscles (Reuters)

“Run faster, run longer, be more active, be active for longer periods of your daily cycle, be active for longer periods of the year, and increase your foraging space. The possibilities are endless. But all this It has a great cost. More energy requires more food, more foraging, and so on. It is a good balance between the energy that is consumed and that which is ingested,” added Arrojo.

Mammal lineage They evolved from cold-blooded creatures, some of which feature strange body structures, Such as Dimetrodonwhich blends reptile traits, such as extended legs, and mammals, such as the arrangement of certain jaw muscles.

The endothermic Came relatively quickly Perhaps in less than a million years, rather than a longer, gradual process, according to a paleontologist and study co-author Roman David From Natural History Museum, London.

was the early example Kind vaguely resembles a weasel, The Pseudotherium argentinus, In Argentina about 231 million years ago. were the later true mammals The ancestors of the three groups of present-day mammals: placentas, marsupials, and monotremes.

Among the current animals, warm-blooded mammals and birds (Reuters)
Among the current animals, warm-blooded mammals and birds (Reuters)

“Given the importance of heat absorption in many aspects of body planning, physiology, and lifestyle of modern mammals, When our ancient ancestors evolved this was a really important unresolved question in paleontology.” Paleontologist and co-author of the study reassured Ken Angelcic, From Chicago Field Museum.

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For Araujo, it was difficult to determine when the heat originated from fossils. He said, “We can’t put thermometers in your pet’s armpit, can we?” however, The inner ear provided a solution. The viscosity or fluidity of the inner ear fluid – and all liquids – It changes with temperature.

In cold-blooded animals, this fluid is colder and thicker, requiring wider ducts, and in warm-blooded animals it is less viscous and the semicircular ducts are smaller. researchers Comparing the semicircular canals of 341 animals, 243 extant and 64 extinct. this is showed that heat absorption came millions of years later than some previous estimates.

Mammals have played a minor role in the ecosystems it dominates dinosaurs Before taking over after the mass extinction 66 million years ago. Among the living animals, mammals and birds are warm-blooded.

With information from Reuters

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