THE SKULL OF <i>ICTOPS</i> AND THE CLASSIFICATION OF THE INSECTIVORA

<jats:title>SUMMARY</jats:title><jats:p>The skull of the leptictid insectivore <jats:italic>Ictops,</jats:italic> from the White River Oligocene, is redescribed, and compared with <jats:italic>Echinosorex</jats:italic> and other primitive Erinaceidae. It is concluded that <jats:italic>Ictops</jats:italic> is much more primitive than any known erinaceid, and at the same time possesses characters which indicate that the Leptictidae and Erinaceidae have specialized in divergent directions. The characters which <jats:italic>Ictops</jats:italic> shares with the Erinaceidae are almost wholly primitive insectivore characters, not indicative of special relationship. The Leptictidae are therefore removed from the Erinaceoidea and placed in a separate superfamily, the Leptictoidea.</jats:p><jats:p>A new classification of the insectivores is proposed, based on characters of the skull. The Lipotyphla are regarded as an order, with two suborders: (1)Erinaceomorpha, a primitive group consisting of the Leptictoidea and Erinaceoidea; (2)Soricomorpha, a specialized group, probably derived from an erinaceomorph ancestry, and comprizing the Tenrecoidea, Soricoidea and Chrysochloroidea. The chrysoehlorids are regarded as highly specialized derivatives of a soricomorph stock. The Macroscelididae, Tupaiidae, Lemuroidea and Dermoptera are interpreted as forming a natural group (Archonta), with an ancestry near the Erinaceomorpha. The Macroscelididae are related to the Tupaiidae, and thus to the Primates; they are in some ways more primitive than the Tupaiidae, and have developed in a divergent direction, in some respects paralleling the Erinaceidae. They are not closely related to the Lipotyphia, and are placed in a new order, Macroscelidea. The superorder Archonta thus consists of three orders: (1)Macroscelidea, (2)Dermoptera (3)Primates (including Tupaiidae).</jats:p>