Therapsid - Wikipedia
The therapsids are usually placed in the class Reptilia as its most mammal-like representatives. . related to the development of the teeth. The foramina in. Nonmammalian synapsids, or “Mammal-like reptiles” Dimetrodon, a sphenacosaurid therapsid. – Size of a St. Bernard dog relationship to metabolic rate. Examines the ancestors of mammals and their evolution into mammals. mammals evolved and how living mammalian species are related to one another. . Some therapsids, in turn, may have been ancestral to mammals.
Like all land animals, the therapsids were seriously affected by the Permian—Triassic extinction event ; the very successful gorgonopsians dying out altogether and the remaining groups - dicynodontstherocephaliansand cynodonts - reduced to a handful of species each by the earliest Triassic. The dicynodonts, now represented by a single family of large stocky herbivoresthe Kannemeyeridaeand the medium-sized cynodonts including both carnivorous and herbivorous formsflourished worldwide throughout the Early and Middle Triassic.
They disappear from the fossil record across much of Pangea at the end of the Carnian Late Triassicalthough they continued for some time longer in the wet equatorial band and the south. Lemurosaurus Some exceptions were the still further derived eucynodonts. At least three groups of them survived.
They all appeared in the Late Triassic period. The extremely mammal-like family, Tritylodontidaesurvived into the Early Cretaceous.
Another extremely mammal-like family, Tritheledontidaeare unknown later than the Early Jurassic. Mammaliaformes was the third group, including Morganucodon and similar animals. Many taxonomists refer to these animals as " mammals ", though some limit the term to the mammalian crown group. The non-eucynodont cynodonts survived the Permian-Triassic extinction; ThrinaxodonGalesaurus and Platycraniellus are known from the Early Triassic.
By the Middle Triassichowever, only the eucynodonts remained.
The evidence was their anatomical features such as the skull, and the vertebrae. Therapsid temporal fenestrae the paired extra holes in their skulls behind the eyes were larger than those of the pelycosaurs.INTERVIEW WITH TRIASSIC MAMMALS
Endothermy warm-bloodedness in therapsids is speculated to have arisen by the Middle or Late Permian Dinocephalians and anomodonts were probably warm-blooded.
Therapsids probably had naked skin, like that of mammalsrather than scales as in reptiles and pelycosaurs. Early therapsids did not have furwhich developed in the Middle or Late Permian, in the theriodonts. Therapsids became the dominant land animals by the Middle Permian, replacing the pelycosaurs. Therapsida comprises three major clades: After a brief burst of evolutionary diversity, the dinocephalians died out in the later Middle Permian, but the anomodont dicynodonts and the theriodont gorgonopsians and therocephalians flourished, being joined at the very end of the Permian by the first Cynodonts.
The Cynodonts were the most mammal-like of the therapsids. Therapsids were by far the most diverse and abundant large animals of the Middle and Late Permian, including a diverse range of herbivores and carnivores, ranging from small animals the size of a rat for example, Robertiato large bulky herbivores a ton or more in weight for example, Moschops. After flourishing for many millions of years, these successful animals were all but wiped out by the Permian-Triassic mass extinction about million years ago, the largest extinction in Earth's history.
According to the fossil record, only a few therapsids and no pelycosaurs, survived the Permian extinction and went on to be successful in the new early Triassic landscape.
Therapsid | fossil tetrapod order | shizutetsu.info
The very successful gorgonopsians died out altogether and the remaining groups were represented by only one or two families of a few species, each surviving into the Triassic. Of these, the dicynodonts, now represented by a single family of large stocky herbivores, the Kannemeyeridae, and the medium-sized cynodonts including both carnivorous and herbivorous formsflourished worldwide, throughout the Early and Middle Triassic.
They died out across much of Pangea at the end of the Late Triassic, although they continued for some time longer in the wet equatorial band and the south. Some exceptions were the still further derived eucynodonts. At least three groups of them survived. The extremely mammal-like family, Tritylodontidae, survived into the Early Cretaceous An extremely mammal-like family, Tritheledontidae, are unknown later than the Early Jurassic The third group, Morganucodon and similar animals, were stem-mammals Dicynodonts are thought to have become extinct before the end of the Triassicbut there is evidence that they survived the extinction.
Evolution of mammals
Their fossils have been found in Gondwana. Other animals that were common in the Triassic also took refuge here, such as the Temnospondyls. Vertebrate Paleontology, 3rd ed.