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Mammals

Euchambersia, an extinct genus of therocephalians, is hypothesized to have had venom glands attached to its canine teeth.

A few species of living mammals are venomous, including solenodons, shrews, vampire bats, male platypuses, and slow lorises. Shrews have venomous saliva and most likely evolved their trait similarly to snakes. The presence of tarsal spurs akin to those of the platypus in many non- therian Mammaliaformes groups suggests that venom was an ancestral characteristic among mammals.

Extensive research on platypuses shows that their toxin was initially formed from gene duplication, but data provides evidence that the further evolution of platypus venom does not rely as much on gene duplication as was once thought. Modified sweat glands are what evolved into platypus venom glands. Although it is proven that reptile and platypus venom have independently evolved, it is thought that there are certain protein structures that are favored to evolve into toxic molecules. This provides more evidence of why venom has become a homoplastic trait and why very different animals have convergently evolved.