A few mammals possess venom. Shrews have a toxic saliva. Some monkeys secrete a poison from their "armpit" and lick it to give them a venomous bite. The male Platypus has spurs on theirs back legs...
Ornithorhynchus anatinus aka Platypus. Note. Only the male is venomous, with a spur on each hind leg. It is unlike most other mammals. The largest mammal group, Eutheria, give birth to fully...