Tritheledontidae, the tritheledontids or ictidosaurs, is an

extinct 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 last individual of the species, although the capacity to breed and ...

family of small to medium-sized (about 10 to 20 cm long)

cynodont The cynodonts () (clade Cynodontia) are a clade of eutheriodont therapsids that first appeared in the Late Permian (approximately 260 mya), and extensively diversified after the Permian–Triassic extinction event. Cynodonts had a wide variety ...

s. They were highly

mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...

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

reptile Reptiles, as most commonly defined are the animals in the class Reptilia ( ), a paraphyletic grouping comprising all sauropsids except birds. Living reptiles comprise turtles, crocodilians, squamates (lizards and snakes) and rhynchocephalians ( ...

-like anatomical traits. Tritheledontids were mainly

carnivorous A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose food and energy requirements derive from animal tissues (mainly muscle, fat and other sof ...

insectivorous A robber fly eating a hoverfly An insectivore is a carnivorous animal or plant that eats insects. An alternative term is entomophage, which can also refer to the human practice of eating insects. The first vertebrate insectivores were ...

, 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 to the Jurassic 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, indicating that they may have lived only on the supercontinent of

Gondwana Gondwana () was a large landmass, often referred to as a supercontinent, that formed during the late Neoproterozoic (about 550 million years ago) and began to break up during the Jurassic period (about 180 million years ago). The final stages ...

. The family Tritheledontidae was named by South African paleontologist Robert Broom in 1912. May be downloaded from: https://archive.org/details/annalsofsouthafr07sout The family is often misspelled "Trithelodontidae". It is possible that tritheledontids had

vibrissae Vibrissae (; singular: vibrissa; ), more generally called Whiskers, are a type of stiff, functional hair used by mammals to sense their environment. These hairs are finely specialised for this purpose, whereas other types of hair are coarse ...

, 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.

Genera

* '' Chaliminia'' * '' Diarthrognathus'' * ''

Elliotherium ''Elliotherium'' is an extinct genus of cynodonts which existed in South Africa during the upper Triassic period. The type species is ''Elliotherium kersteni'', named after the Elliot Formation The Elliot Formation is a geological formation a ...

'' * ''

Irajatherium ''Irajatherium'' is an extinct genus of cynodonts, known only of the type species ''Irajatherium hernandezi''.Martinelli et al., 2005 It is named in honor of Irajá Damiani Pinto. Species ''Irajatherium hernandezi'' is a species known only by ...

'' * '' Pachygenelus'' * '' Riograndia'' * ''

Tritheledon ''Tritheledon'' is an extinct genus of cynodonts that lived during the Lower Jurassic. Fossils were found in the Elliot Formation, South Africa. Like all cynodonts, it had many traits shared by mammals. Tritheledonts were probably insectivores, ...

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

Genera

See also

References

External links