More than 252 million years ago, mammal ancestors became warm-blooded to survive mass extinction
July 18, 2017 by Kevin Rey, The Conversation
Today, mammals and birds are the only true warm-blooded animals. They are called endotherms, meaning they produce their body heat internally.
Endotherm animals are the opposite to ectotherms which get their heat from an external factor like the sun. They are considered "cold-blooded".
The origins of warm-bloodedness in mammals has been a very controversial issue for two reasons. One is that several of the anatomical features thought to be linked to warm-bloodedness have also been found in cold-blooded reptiles. The other is that these characteristics are not always preserved in fossils, giving scientists inconsistent signals about the presence of warm-bloodedness.
Read more at:
https://phys.org/news/2017-07-million-years-mammal-ancestors-warm-blooded.html#jCp
