Warm-blooded animals appeared 233 million years ago, study finds

  Recently, scientists have answered a long-standing question about mammalian evolution – by dissecting the ears of living and extinct mammals and their relatives, they have determined that warm-blooded animals may have originated in the late late 1990s about 233 million years ago. Triassic. These findings, based on the fossilized inner ear of mammalian ancestors, have improved our understanding of mammalian evolutionary history.
  Warm-blooded, or endothermic, is a key characteristic of mammals and birds that allows them to maintain a near-constant core body temperature to live in a variety of environments. Studying the structure of the semicircular canals of the inner ear in mammalian ancestors helps to understand when the mammalian transition to endothermia began. The scientists studied changes in semicircular canal structure in 56 extinct species that were the ancestors of mammals and found changes associated with endothermicity, such as narrowing of the semicircular canals.