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The early synapsids spread and diversified, becoming the largest terrestrial animals in the latest Carboniferous and Early Permian periods, ranging up to 6 metres (20 ft) in length. They were sprawling, bulky, possibly cold-blooded, and had small brains. Some, such as Dimetrodon, had large sails that might have helped raise their body temperature.
Dinosaurs were initially cold-blooded, but global warming 180 million years ago may have triggered the evolution of warm-blooded species, a new study found.
They were warm-blooded, more like modern mammals or birds than modern reptiles. They were neither cold-blooded nor warm-blooded in modern terms, but had metabolisms that were different from and in some ways intermediate between those of modern cold-blooded and warm-blooded animals. They included animals with two or three of these types of ...
The Dinosaur Heresies: New Theories Unlocking the Mystery of the Dinosaurs and Their Extinction is a 1986 book written by Robert T. Bakker [1] [2] exploring extant evidence indicating that dinosaurs, rather than being cold-blooded and wholly lizard-like, were warm-blooded, agile creatures more similar to modern birds than to lizards or other reptiles.
Cold-blooded animals, including reptiles like snakes and lizards, depend on outside sources to control their temperature: For example, basking in the sun to warm up. Knowing when dinosaurs evolved their stable internal thermometer could help scientists answer other questions about how they lived, including how active and social they were. To ...
But scientists observed differences between the two big groups of dinosaurs, finding that Triceratops were cold-blooded and T-Rex warm-blooded.
In his 1986 work The Dinosaur Heresies, Bakker puts forth the theory that dinosaurs were warm-blooded. His evidence for this includes: Almost all modern animals that walk upright are warm-blooded, and dinosaurs walked upright. The hearts of warm-blooded animals can pump much more effectively than the hearts of cold-blooded animals.
The synapsid lineage became distinct from the sauropsid lineage in the late Carboniferous period, between 320 and 315 million years ago. [2] The only living synapsids are mammals, [3] while the sauropsids gave rise to the dinosaurs, and today's reptiles and birds along with all the extinct amniotes more closely related to them than to mammals. [2]