Probainognathia is one of the two major subgroups of the clade Eucynodontia, the other being Cynognathia. The earliest forms were carnivorous and insectivorous, though some groups eventually also evolved herbivorous diets. The earliest and most basal probainognathian is the

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 in chronostratigraphy. The Middle Triassic spans the time between Ma an ...

(

Anisian In the geologic timescale, the Anisian is the lower stage or earliest age of the Middle Triassic series or epoch and lasted from million years ago until million years ago. The Anisian Age succeeds the Olenekian Age (part of the Lower Triassic ...

) aged '' Lumkuia'', from

South Africa South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring coun ...

, though probainognathians would not become prominent until the mid Norian stage of the Late Triassic. Three groups survived the

extinction Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the Endling, last individual of the species, although the Functional ext ...

at the end of Triassic: Tritheledontidae and

Tritylodontidae Tritylodontidae ("three-knob teeth", named after the shape of their cheek teeth) is an extinct family of small to medium-sized, highly specialized mammal-like cynodonts, bearing several mammalian traits like erect limbs, endothermy and details ...

, which both survived until the

Jurassic The Jurassic ( ) is a geologic period and stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The Jurassic constitutes the middle period of ...

—the latter even into the

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

('' Montirictus'' and ''

Xenocretosuchus ''Xenocretosuchus'' is an extinct genus of tritylodont therapsids from the Aptian (Early Cretaceous) Ilek Formation of Siberia, in the Russian Federation. The type species, ''X. sibiricus'', is known only from dental elements, as is ''X. koloss ...

'')—and

Mammaliaformes Mammaliaformes ("mammalian forms") is a clade that contains the crown group mammals and their closest extinct relatives; the group radiated from earlier probainognathian cynodonts. It is defined as the clade originating from the most recent c ...

, which includes the mammals.The slow and fast steps to becoming a mammal
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Phylogeny

Below is a cladogram from Ruta, Botha-Brink, Mitchell and Benton (2013) showing one hypothesis of cynodont relationships:

References

{{Taxonbar, from=Q950661 Extant Middle Triassic first appearances Taxa named by James Hopson

Phylogeny

See also

References