Scientists discovered that mammals appeared much earlier than previously believed, especially 20 million years ago what has been established so far. Examination of jaws in fossils Brasilodon quadrangleA mouse about 20 centimeters long that lived 225 million years ago allowed this discovery.
analysis the different growth stages presented by the teeth in each of the fossils These remains were found to be allowed to indicate that they belonged to a mammal.
Previously, the earliest accepted record of mammalian geological time was 205 million years ago. This new research reveals a much older origin of mammals, specifically 20 million years later.
“Evidence of how teeth are built during development crucial and conclusive to prove that brazilodonts are mammals. Our paper demonstrates their origin in the fossil record much earlier than previously known,” said Moya Meredith Smith, contributing author and Professor of Evolution and Development of Dentoskeletal Anatomy at King’s College London.
The mammary glands that produce milk and feed the young mammals today have not been preserved in any fossils found so far. Therefore, scientists had to rely on “hard tissues”, mineralized bone and fossilized teeth for alternative clues.
By examining teeth found in fossils Brasilodon quadrangle The research team from southern Brazil, dated to around 225 million years ago (Upper Triassic/Norian), discovered evidence of a single set of spare teeth. This is an important feature of mammals known as diphodontia.
The first set of teeth begins to develop at the embryonic stage, and the second and final set of teeth develops after the animal is born. In contrast, reptilian dentitions are different, especially since replacement is “one-to-one” (polyphodontia), where each tooth has multiple tooth regenerations to replace damaged teeth during a reptile’s lifetime.
Diphyodontia is a complex and unique phenomenon involving deep and time-controlled changes in the anatomy of the skull along with tooth replacement, for example, the closure of the secondary palate (roof of the mouth) that allows the young to suck while simultaneously breathing.
Reference work: https://onlinelibrary.wiley.com/doi/10.1111/joa.13756
……
Environment department contact address:[email protected]