The Cynognathians are one of the two major clades of the infraorder 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...

, the other being the Probainognathia

Probainognathia

The Probainognathians are one of the two major clades of the infraorder Eucynodontia, the other being Cynognathians. They were mostly carnivorous, though some species may have evolved omnivorous traits. The Probainognathia form into four groups: Probainognathidae, Chiniquodontidae,...

ns. Cynognathus

Cynognathus

Cynognathus crateronotus was a meter-long predator of the Early to Middle Triassic. It was among the more mammal-like of the Synapsids, a member of a grouping called Eucynodontia. The genus Cynognathus had an almost worldwide distribution...

, the most basal representative of the clade was a carnivore, unlike most cynognathians. The cynognathians were mostly 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...

-like, but the subgroup Tritylodontids were the most mammal-like. Cynognathians can be identified by several synapomorphies including a very deep zygomatic arch

Zygomatic arch

The zygomatic arch or cheek bone is formed by the zygomatic process of temporal bone and the temporal process of the zygomatic bone , the two being united by an oblique suture; the tendon of the Temporalis passes medial to the arch to gain insertion into the coronoid process...

 that extends above the middle of the orbit

Orbit (anatomy)

In anatomy, the orbit is the cavity or socket of the skull in which the eye and its appendages are situated. "Orbit" can refer to the bony socket, or it can also be used to imply the contents...

. The cynognathians are the longest lived therapsid non-mammalian clade extending from Triassic

Triassic

The Triassic is a geologic period and system that extends from about 250 to 200 Mya . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events...

 to the Early Cretaceous

Early Cretaceous

The Early Cretaceous or the Lower Cretaceous , is the earlier or lower of the two major divisions of the Cretaceous...

. The most renowned Cynognathian is Cynognathus

Cynognathus

Cynognathus crateronotus was a meter-long predator of the Early to Middle Triassic. It was among the more mammal-like of the Synapsids, a member of a grouping called Eucynodontia. The genus Cynognathus had an almost worldwide distribution...

.

So far, their fossils are found in South America

South America

South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...

, Antarctica, and South Africa

South Africa

The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...

.

Taxonomy

• Suborder Cynodontia
  • Infraorder 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...
    
    
    • (unranked) Cynognathia
      • Family Cynognathidae
        • Cynognathus
          Cynognathus
          Cynognathus crateronotus was a meter-long predator of the Early to Middle Triassic. It was among the more mammal-like of the Synapsids, a member of a grouping called Eucynodontia. The genus Cynognathus had an almost worldwide distribution...
          
          
      • Superfamily Tritylodontoidea
        • Family Diademodontidae
        • Family ?Trirachodontidae
          Trirachodontidae
          Trirachodontidae is an extinct family of cynognathian cynodonts from the Triassic of China and southern Africa. Trirachodontids appeared during the Early Triassic soon after the Permian-Triassic extinction event and quickly spread over a wide geographic area in a comparatively brief amount of time...
          
          
        • Family Traversodontidae
          Traversodontidae
          Traversodontidae is a family of herbivorous cynodonts. Traversodonts were primarily Gondwanan, with many species known from Africa and South America. Recently, traversodonts have also been found from Europe and eastern North America. Traversodonts first appeared in the Middle Triassic, diversified...
          
          
          • Massetognathus
            Massetognathus
            A relative of Cynognathus, Massetognathus was a plant-eating cynodont belonging to the Traversodontid family. This cynodont lived in what is now South America, in Brazil and Argentina during the Middle Triassic period .Massetognathus was about long. It had cheek teeth specially adapted to...
            
            
        • Family Tritylodontidae
          Tritylodontidae
          Tritylodontids were small to medium-sized, highly specialized and extremely mammal-like cynodonts. They were the last family of the non-mammalian synapsids. One of the last cynodont lines to appear, the Tritylodontidae descended from a Cynognathus-like cynodont...
          
          
          • Oligokyphus
            Oligokyphus
            Oligokyphus was an advanced herbivorous cynodont of the late Triassic to early Jurassic periods. Originally considered to be an early mammal, it is now classified as a synapsid because Oligokyphus does not have the mammalian jaw attachments and it retains a vestigial joint between the quadrate...
            
            
          • Tritylodon
            Tritylodon
            Trityldon was a genus of tritylodont, one of the most advanced group of cynodont therapsids. They lived in the Early Jurassic and possibly Late Triassic periods along with dinosaurs. They also shared a lot of characteristics with mammals, and were once considered mammals because of overall...
            
            
          • Bienotherium
            Bienotherium
            Bienotherium was a therapsid from the Early Jurassic of China. Despite its size, it is closely related to Lufengia, and is the largest tritylodont from the Lufeng Formation in China....
            
            

See also

• Evolution of mammals
  Evolution of mammals
  __FORCETOC__The evolution of mammals within the synapsid lineage was a gradual process that took approximately 70 million years, beginning in the mid-Permian. By the mid-Triassic, there were many species that looked like mammals, and the first true mammals appeared in the early Jurassic...
  
  
• Mammaliaformes
  Mammaliaformes
  Mammaliaformes is a clade that contains the mammals and their closest extinct relatives. Phylogenetically, it is defined as a clade including the most recent common ancestor of Sinoconodon, morganuconodonts, docodonts, Monotremata, Marsupialia, Placentalia, extinct members of this clade, and all...
  
  
• Prehistoric mammal
  Prehistoric mammal
  Prehistoric mammals are groups of mammals that lived before humans developed writing. 164 million years ago, in the Jurassic period, Castorocauda lutrasimilis, a mammal-like animal weighing about 500 grams , had a full mammalian pelt, with guard hairs and under fur, webbed feet, and scales on the...
  
  s