Tritheledontidae, the tritheledontids or ictidosaurs, is an extinct family of small to medium-sized (about 10 to 20 cm long) cynodonts. They were highly

mammal A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...

-like, specialized cynodonts, although they still retained a few

reptile Reptiles, as commonly defined, are a group of tetrapods with an ectothermic metabolism and Amniotic egg, amniotic development. Living traditional reptiles comprise four Order (biology), orders: Testudines, Crocodilia, Squamata, and Rhynchocepha ...

-like anatomical traits. Tritheledontids were mainly carnivorous or insectivorous, though some species may have developed omnivory. Their skeletons show that they had a close relationship to mammals. Tritheledontids or their closest relatives may have given rise to the mammaliaforms. The tritheledontids were one of the longest lived non-mammalian therapsid lineages, living from the late

Triassic The Triassic ( ; sometimes symbolized 🝈) is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.4 Mya. The Triassic is t ...

to the

Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately 143.1 Mya. ...

period. Tritheledontids became extinct in the Jurassic period, possibly due to competition with prehistoric mammals such as the eutriconodonts. They are known from finds in South America and

South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. Its Provinces of South Africa, nine provinces are bounded to the south by of coastline that stretches along the Atlantic O ...

, indicating that they may have lived only on the supercontinent of Gondwana. The family Tritheledontidae was named by South African paleontologist

Robert Broom Robert Broom Fellow of the Royal Society, FRS FRSE (30 November 1866 6 April 1951) was a British- South African medical doctor and palaeontologist. He qualified as a medical practitioner in 1895 and received his DSc in 1905 from the University ...

in 1912. The family is often misspelled "Trithelodontidae". It is possible that tritheledontids had vibrissae, according to the PBS documentary, ''Your Inner Fish''. A common ancestor of all therian mammals did so. It is possible that the development of the whisker sensory system played an important role in mammalian development, more generally.

Phylogeny

Cladogram after Ruta, Botha-Brink, Mitchell and Benton (2013):

References

External links

PBS YouTube animated video
of a tritheledontid {{Taxonbar, from1=Q21646750, from2=Q140837 Late Triassic first appearances Middle Jurassic extinctions Prehistoric therapsid families

Phylogeny

See also

References

External links