Scientists discover the oldest mammal on Earth in Brazil

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A team of Brazilian and English paleontologists discovered the oldest mammals in the world. The work of nearly 20 years revealed that fossils found in the central region of Rio Grande do Sul belong to a species of rodent.

The research was based on microscopic analysis of the jaws and teeth of cynodonts called Brasilodon quadrangularis, which were found fossilized in rocks from the Triassic period in the state.

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The ancient relatives of capybaras lived in the south of the country 225 million years ago.

The findings were published in the Journal of Anatomy on September 6.

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The small brazilodotids were 20 centimeters long and weighed just over 15 grams. They resembled today’s small rodents, but to this day were described in the scientific literature as having a reptilian biological nature, the researchers said.

Sergio Furtado Cabreira, PhD in Geology and researcher on the project, said in a statement that “since the first cynodont fossils were found, in the second half of the 19th century, these small fossils were described as ectothermic and oviparous animals, that is, cold-blooded. and lay eggs for their reproduction”.

However, “our research showed, through microscopic analysis of the jaws and teeth, that these small animals already had diphodontia, that is, only a permanent dentition replacing the milk dentition”, explains Cabreira.

Diphodontia is directly associated, in current mammals, with physiological characteristics such as endothermy, placentation and lactation, says the team. This means that brasilodontids were tiny endothermic (warm-blooded) furry animals and would produce litters of live-born offspring, which would then be suckled by their mothers.

Characteristics of Brasilodon quadrangularis

The first histological work with the dentitions of these fossils that are at the Federal University of Rio Grande do Sul began in March 2004, when paleontologists selected some isolated jaws of the fossil, only 2.0 cm long, for the preparation and manufacture of histological slides and further study under different microscopes.

According to the researcher, the main findings occurred because the enamel and other mineralized dental tissues of the animals have information about basic characteristics of the metabolic conditions in which they are formed.

In this way, explained Cabreira, it was possible to diagnose which teeth would have started their formation during the placental development phase of an embryo, and which teeth would have formed after the animals were born.

Furthermore, research has shown that these mammals from the Triassic Period were nocturnal animals that hunted insects and small reptiles and were supposed to live in small burrows where their young lived until they became adults.

More surprising, the discovery points out that certain characteristics of some orders of mammals such as Marsupials and Monotremes would have emerged as secondary reproductive elements, through the evolution of placental ancestors,” said Cabreira.

Scientists classify the discovery as relevant, since it shows that placental mammals are as old as the first dinosaurs and brings important information about the conservatism and continuity of genetic, embryological and physiological patterns of vertebrates over time.

“Finally, this innovative work in evolutionary biology can bring new perspectives to illuminate the scenario on the evolution and dentition of mammals”, says the researcher.



Source: CNN Brasil

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