Therocephalians were a suborder of therapsids, ancestors of mammals, that dominated the Earth during the mid-late Permian and early Triassic. They were successful carnivores with early mammal-like features, including fur and whiskers, and at least one species was venomous. Therocephalians were replaced by archosaurs about 235 million years ago during the “Triassic Takeover”. They fed on pareiasaurs, tapinocephali, and large dicynodonts.
The Therocephalians (“beast-heads”) were an extinct suborder of therapsids therodons (Permian/Triassic ancestors of mammals) that were among the dominant animals on Earth during the mid-late Permian and early Triassic, up to the archosaurs ( the ancestors and relatives of dinosaurs) took over about 235 million years ago. Therocephalian fossils are dated between about 275 and about 235 million years ago. The large skulls and teeth of therocephalus indicate that they were successful carnivores. Therocephalians had some early mammal-like features, including fur and whiskers. At least some species were warm-blooded. At least one species (Euchambersia) had a maximal fossa and grooved caniform teeth, indicative of a venom gland, which would make therocephalians the earliest known venomous vertebrates.
Therocephalians were part of the second wave of synapsid (mammal ancestor) life development, conquering the land in the mid to late Permian, competing with and replacing relatives that had branched out earlier, such as other synapsids, including the famous pelycosaurs, extinct in the mid-Permian. Therocephalians evolved on Earth during a time when synapsids had been the dominant land animal for several tens of millions of years, supplanting the amphibian-dominated Carboniferous fauna.
Therocephalians are unique in being synapsids that began their careers as dominant predators, top ecosystems for about twenty million years, barely survive the largest mass extinction in planetary history (the Permian-Triassic extinction), then continue to see rival reptilians (archosaurs) outrun them in an event known as the “Triassic Takeover”, the exact causes of which are still unknown. It may have something to do with the planet’s increasing aridity during that time, favoring reptiles. Reptiles excrete uric acid instead of urea, a more effectively water-conserving form of excretion, urea, used by mammals today and by synapsids (including therocephalians) at the time.
The cynodonts, the Triassic ancestors of mammals, were another suborder of therodons related to the therocephalus. Together, both groups constituted the most powerful predators and omnivores of the Late Permian/early Triassic, corresponding to today’s carnivores. Therocephalians would have fed on pareiasaurs, herbivorous anapsids (reptiles without holes in the skull, such as turtles), which ranged in size from 60 cm (22 in) to 3 m (10 ft), tapinocephali (ton-sized synapsids with thick heads ) and large dicynodonts (rat to ox-sized therapsids that were among the most successful animals in the immediate Permian-Triassic extinction, in some places representing 99% of all vertebrate faunas).
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