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When did mammals evolve?
When did mammals become synapsids?
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t. e. The evolution of mammals has passed through many stages since the first appearance of their synapsid ancestors in the Pennsylvanian sub-period of the late Carboniferous period. By the mid- Triassic, there were many synapsid species that looked like mammals.
- Overview
- The evolution of the mammalian condition
Mammals were derived in the Triassic Period (about 252 million to 201 million years ago) from members of the reptilian order Therapsida. The therapsids, members of the subclass Synapsida (sometimes called the mammal-like reptiles), generally were unimpressive in relation to other reptiles of their time. Synapsids were present in the Carboniferous Period (about 359 million to 299 million years ago) and are one of the earliest known reptilian groups. They were the dominant reptiles of the Permian Period (299 million to 252 million years ago), and, although they were primarily predaceous in habit, the adaptive radiation included herbivorous species as well. In the Mesozoic Era (about 252 million to 66 million years ago), the most important of the synapsids were the archosaurs, or “ruling reptiles,” and the therapsids were, in general, small active carnivores. Therapsids tended to evolve a specialized heterodont dentition (that is, a set of teeth separated into molars, incisors, and canines) and to improve the mechanics of locomotion by bringing the plane of action of the limbs close to the trunk. A secondary palate was developed, and the temporal musculature, the muscle involved in closing the jaw, was expanded.
The several features that separate modern reptiles from modern mammals doubtless evolved at different rates. Many attributes of mammals are correlated with their highly active habit—for example, efficient double circulation with a completely four-chambered heart, anucleate and biconcave erythrocytes, the diaphragm, and the secondary palate (which separates passages for food and air and allows breathing during mastication or suckling). Hair for insulation is a correlate of endothermy, or warm-bloodedness, the physiological maintenance of individual temperature independent of environmental temperature. Endothermy allows high levels of sustained activity. The unique characteristics of mammals thus would seem to have evolved as a complex interrelated system.
Mammals were derived in the Triassic Period (about 252 million to 201 million years ago) from members of the reptilian order Therapsida. The therapsids, members of the subclass Synapsida (sometimes called the mammal-like reptiles), generally were unimpressive in relation to other reptiles of their time. Synapsids were present in the Carboniferous Period (about 359 million to 299 million years ago) and are one of the earliest known reptilian groups. They were the dominant reptiles of the Permian Period (299 million to 252 million years ago), and, although they were primarily predaceous in habit, the adaptive radiation included herbivorous species as well. In the Mesozoic Era (about 252 million to 66 million years ago), the most important of the synapsids were the archosaurs, or “ruling reptiles,” and the therapsids were, in general, small active carnivores. Therapsids tended to evolve a specialized heterodont dentition (that is, a set of teeth separated into molars, incisors, and canines) and to improve the mechanics of locomotion by bringing the plane of action of the limbs close to the trunk. A secondary palate was developed, and the temporal musculature, the muscle involved in closing the jaw, was expanded.
The several features that separate modern reptiles from modern mammals doubtless evolved at different rates. Many attributes of mammals are correlated with their highly active habit—for example, efficient double circulation with a completely four-chambered heart, anucleate and biconcave erythrocytes, the diaphragm, and the secondary palate (which separates passages for food and air and allows breathing during mastication or suckling). Hair for insulation is a correlate of endothermy, or warm-bloodedness, the physiological maintenance of individual temperature independent of environmental temperature. Endothermy allows high levels of sustained activity. The unique characteristics of mammals thus would seem to have evolved as a complex interrelated system.
A series of prehistoric creature illustrations demonstrates the evolution of mammals through the ages. More fact than fiction, these wild characters followed transitional Jurassic period animals ...
- Rick Gore
Oct 31, 2023 · The evolution of mammals passed through many stages since the first appearance of their synapsid ancestors in the late Carboniferous period. Mammals are synapsids: they have a single opening in the skull. They are the only living synapsids as earlier forms became extinct by the Jurassic period.
Apr 2, 2020 · These early mammals were small, insectivorous, nocturnal, hairy and warm blooded animals. Warm-bloodedness is believed to have first evolved among the cynodonts, a late but successful group of mammal-like reptiles, from which the mammals evolved.
Nov 11, 2020 · This interest in the evolution of mammals and plants at the end of the Cretaceous period has only arisen quite recently, although some mammal relics were already described in the original discovery of the dinosaurs in 1824 when naturalist William Buckland presented bones from one of the first known dinosaurs, Megalosaurus, at the Geological Soci...
Oct 23, 2019 · 23 October 2019. How the earliest mammals thrived alongside dinosaurs. An explosion of fossil finds reveals that ancient mammals evolved a wide variety of adaptations allowing them to exploit...
