Primates exhibit a wide range of characteristics. Some primates do not live primarily in trees, but all species possess adaptations for climbing trees. Locomotion techniques used include leaping from tree to tree, walking on two or four limbs, knuckle-walking, and swinging between branches of trees (known as brachiation). Primates are characterized by their large brains relative to other mammals. These features are most significant in monkeys and apes, and noticeably less so in lorises and lemurs. Many species are sexually dimorphic, which means males and females have different physical traits, including body mass, canine tooth size, and coloration.
Saadanius is a genus of fossil primate dating to the Oligocene that is closely related to the common ancestor of the Old World monkeys and apes, collectively known as catarrhines. It is represented by a single species, Saadanius hijazensis, which is known only from a single partial skull tentatively dated between 29 and 28 mya (million years ago). It was discovered in 2009 in western Saudi Arabia near Mecca and was first described in 2010 after a comparison with both living and fossil catarrhines. Saadanius had a longer face than living catarrhines and lacked the advanced frontal sinus (airspaces in the facial bones) found in living catarrhines. However, it had a bony ear tube (ectotympanic) and teeth comparable to those of living catarrhines. The discovery of Saadanius may help answer questions about the appearance of the last common ancestors of Old World monkeys and apes and help date the evolutionary split between these two primate groups.
Geoffroy's tamarin (Saguinus geoffroyi), also known as the Panamanian, red-crested or rufous-naped tamarin, is a tamarin, a type of small monkey, found in Panama and Colombia. It is predominantly black and white, with a reddish nape. Diurnal, Geoffroy's tamarin spends most of its time in trees, but does come down to the ground occasionally. It lives in groups that most often number between three and five individuals, and generally include one or more adults of each gender. It eats a variety of foods, including insects, exudates, fruits and other plant parts. Insects and fruits account for the majority of its diet, but exudates are also important. But since its teeth are not adapted for gouging trees to get to the sap, it can only eat exudates when they are easily available. Although a variety of reproductive methods are used, the most common is for a single adult female in the group to be reproductively active and to mate with multiple adult males in the group. After a gestation period of about 145 days, she gives birth to either a single infant or twins. Males contribute significantly to care of the infants. Sexual maturity is reached at about 2 years, and it can live up to 13 years. Geoffroy's tamarin is classified as "Least Concern" by the IUCN.