Vertebrate Zoology - V. M. Konstantinov 2011

Chordates
Terrestrial, or Four-Legged, Vertebrates — Amniotes
Class Mammalia — Subclass Theria — Suborder Prosimians, or Lemuriformes

Lower primates are relatively small mammals with a body length ranging from 9 to 106 cm. The tail is usually long (in some species twice the length of the body), non-prehensile, and densely furred. The first digit is not distinctly opposable to the others in all species. In most forms, the digits bear claws rather than Nails. The surface of the Cerebral Cortex is either smooth or bears sulci.

They are distributed in Southeast Asia, Indonesia, Madagascar, and tropical Africa. Currently, 53 species are known (Fig. 196).

In true lemurs (Lemuridae), the upper incisor row is divided by a median gap into left and right halves. The tail is typically long and bushy, and the fur is generally dense. These are arboreal, nocturnal animals that feed partly on fruit and insects, or are omnivorous. They live in social groups. Representative species include the ruffed lemur (Varecia variegatus) and the ring-tailed lemur (Lemur catta); the family Lorisidae includes the slender loris (Loris tardigradus); and the family Daubentoniidae is represented by the aye-aye (Daubentonia madagaskariensis).

Members of the tarsier family (Tarsiidae) are unique animals slightly larger than a rat, featuring enormous forward-facing eyes, very long hind limbs, and short forelimbs (see Fig. 196). Their digits are equipped with adhesive pads. They are arboreal, nocturnal insectivores distributed across the islands of the Malay Archipelago. A representative species is the spectral tarsier (Tarsius spectrum).

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Fig. 196. Lemurs:

1 — aye-aye; 2 — ruffed lemur; 3 — tarsier; 4 — slender loris

Tree shrews (Tupaiidae) are small animals (body length 10–22 cm, tail length 9–22 cm) representing the most primitive prosimians. Their first digits are not opposable. The Brain is relatively small. In appearance, they somewhat resemble small squirrels, with a long, bushy tail and an elongated snout. They inhabit the forests of Southeast Asia.