Procynosuchidae is an extinct family of therapsids which, along with Dviniidae, were the earliest

cynodont Cynodontia () is a clade of eutheriodont therapsids that first appeared in the Late Permian (approximately 260 Megaannum, mya), and extensively diversified after the Permian–Triassic extinction event. Mammals are cynodonts, as are their extin ...

s. They appeared around 260 million years ago, and were most abundant during the latest

Permian The Permian ( ) is a geologic period and System (stratigraphy), stratigraphic system which spans 47 million years, from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.902 Mya. It is the s ...

time (251 mya), shortly before the Permian-Triassic extinction event. Despite being the basal member of the cynodont clade, they already showed some of the advanced mammalian characteristics, but procynosuchids bore resemblance to the

therocephalia Therocephalia is an extinct clade of therapsids (mammals and their close extinct relatives) from the Permian and Triassic periods. The therocephalians ("beast-heads") are named after their large skulls, which, along with the structure of their te ...

ns. Procynosuchid eyes were forward-facing, and the

dentary In jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone ...

was larger than the therocephalians. The procynosuchids had a

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 med ...

, which allows them to eat food while breathing, just like mammals. The procynosuchids became extinct at the Permian-Triassic extinction event. Some procynosuchids were

terrestrial Terrestrial refers to things related to land or the planet Earth, as opposed to extraterrestrial. Terrestrial may also refer to: * Terrestrial animal, an animal that lives on land opposed to living in water, or sometimes an animal that lives on o ...

, but others like ''

Procynosuchus ''Procynosuchus'' (Greek: "Before dog crocodile") is an extinct genus of cynodonts from the Late Permian. It is considered to be one of the earliest and most basal (phylogenetics), basal cynodonts. It was 60 cm (2 ft) long. Remains of ...

'' were semi-aquatic.

References

Cynodontia Prehistoric therapsid families {{Paleo-cynodont-stub