Galesauridae
Encyclopedia
Galesauridae, along with the family Thrinaxodontidae and the large clade
Eucynodontia
(which includes the mammal
s) make up the unranked taxon called Epicynodontia. Galesaurids first appeared in the very latest Permian
period, just a million years (or perhaps only a thousand years) before the greatest extinction of all time, the Permian-Triassic extinction event
.
Galesaurids are the most primitive of the epicynodonts. They may have resembled the basal cynodonts, such as the procynosuchids
and may have descended from a procynosuchid-like ancestor, but the galesaurids were more advanced than the basal cynodont
s. It is clear that, like many other epicynodonts, many galesaurids had a complete secondary palate
, which allowed them to swallow food while breathing, and the dentary bone was enlarged relative to those of their ancestors. Their temporal fenestrae are much larger than those of the procynosuchids, but not as large as in more advanced epicynodonts. Their snouts are broad, rather than tall, and they may have walked erect, with the legs beneath the body like most other cynodonts.
Galesaurid fossils are found almost worldwide. They were among the survivors of the Permian-Triassic extinction event
, but they became extinct in the Middle Triassic
epoch, as did the therocephalia
ns. One of the most notable genera of the family Galesauridae is Galesaurus
.
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
Eucynodontia
Eucynodontia
Eucynodontia is a grouping of animals that includes both mammals, such as dogs, and mammal-like non-mammalian therapsids such as cynodonts . Its membership was and is made up of both carnivores and herbivores. The chronological range extends from at least the Lower Triassic, possibly the Upper...
(which includes the mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
s) make up the unranked taxon called Epicynodontia. Galesaurids first appeared in the very latest Permian
Permian
The PermianThe term "Permian" was introduced into geology in 1841 by Sir Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil; Murchison asserted in 1841 that he named his "Permian...
period, just a million years (or perhaps only a thousand years) before the greatest extinction of all time, the Permian-Triassic extinction event
Permian-Triassic extinction event
The Permian–Triassic extinction event, informally known as the Great Dying, was an extinction event that occurred 252.28 Ma ago, forming the boundary between the Permian and Triassic geologic periods, as well as the Paleozoic and Mesozoic eras...
.
Galesaurids are the most primitive of the epicynodonts. They may have resembled the basal cynodonts, such as the procynosuchids
Procynosuchidae
Procynosuchidae, along with Dviniidae, were the earliest cynodonts. They appeared around 260 million years ago, and were most abundant during the latest Permian time , shortly before the Permian-Triassic extinction event...
and may have descended from a procynosuchid-like ancestor, but the galesaurids were more advanced than the basal cynodont
Cynodont
Cynodontia or cynodonts are a taxon of therapsids which first appeared in the Late Permian and were eventually distributed throughout all seven continents by the Early Triassic . This clade includes modern mammals and their extinct close relatives. They were one of the most diverse groups of...
s. It is clear that, like many other epicynodonts, many galesaurids had a complete secondary palate
Secondary palate
The secondary palate is an anatomical structure that divides the nasal cavity from the oral cavity in many vertebrates.In human embryology, it refers to that portion of the hard palate that is formed by the growth of the two palatine shelves medially and their mutual fusion in the midline...
, which allowed them to swallow food while breathing, and the dentary bone was enlarged relative to those of their ancestors. Their temporal fenestrae are much larger than those of the procynosuchids, but not as large as in more advanced epicynodonts. Their snouts are broad, rather than tall, and they may have walked erect, with the legs beneath the body like most other cynodonts.
Galesaurid fossils are found almost worldwide. They were among the survivors of the Permian-Triassic extinction event
Permian-Triassic extinction event
The Permian–Triassic extinction event, informally known as the Great Dying, was an extinction event that occurred 252.28 Ma ago, forming the boundary between the Permian and Triassic geologic periods, as well as the Paleozoic and Mesozoic eras...
, but they became extinct in the Middle Triassic
Middle Triassic
In the geologic timescale, the Middle Triassic is the second of three epochs of the Triassic period or the middle of three series in which the Triassic system is divided. It spans the time between 245 ± 1.5 Ma and 228 ± 2 Ma...
epoch, as did the therocephalia
Therocephalia
Therocephalians are an extinct suborder of carnivorous eutheriodont therapsids that lived from the middle and late Permian into the Triassic 265.0—245.0 Ma existing for approximately ....
ns. One of the most notable genera of the family Galesauridae is Galesaurus
Galesaurus
Galesaurus was a prehistoric mammal-like-reptile, incorrectly classified as a dinosaur by Sir Richard Owen in 1859. Notably, Galesaurus was mentioned in the first issue of Nature in 1869, where T. H. Huxley expressed confidence that it would eventually be shown to be a dinosaur...
.