Insectivora

Insectivora (infraclass Eutheria, cohort Unguiculata) An order, once recognized, that included the ancestors of all eutherian mammals, nowadays grouped in four orders: Proteutheria, comprising many extinct forms; Scandentia, the tree shrews; Macroscelidea, the elephant shrews; and Lipotyphla, the living hedgehogs, shrews, and moles. The order Insectivora is therefore disbanded. Insectivores are usually small, nocturnal animals showing many primitive features. The dentition is usually full; the teeth resemble those of the earliest mammals. The bony palate is incomplete. In many groups the tympanic cavity is open with no ossified bulla, the tympanic bone forming a partial ring. Limbs are pentadactyl, the gait plantigrade. The brain has large olfactory bulbs but the cerebral hemispheres are small and little convoluted. The stomach is simple. The snout is very sensitive, in some species being drawn into a small trunk. Vibrissae are present on the snout and elsewhere on the body. The sense of hearing is acute, but the eyes are small and eyesight is poor. Some insectivores retain the cloaca. The reproductive system has diverged from the early eutherian form. Fossil forms are known from the Cretaceous and Palaeocene.