The cranium is usually elongate due largely to a long rostrum , but there is a good deal of variation among species. The bullae and carotid circulatory patterns are characteristic, but these characters are difficult to use. The frontal and palatine bones are in contact in the orbit. Crests for the origin of temporal muscles are not well developed. The upper first incisors are separated from each other by a wide space, and the first lower premolars are canine-like.
Molars are tritubercular .
Some species of lemurs are social creatures, living in groups of up to 18 or 20 individuals. Others are usually solitary. Lemurs use scents from a variety of sources for marking their territories and each other, including urine and arm and anal glands. The fossil record of lemurs extends to the Eocene. L. C. Drickamer, S. H. Vessey, and J. F. Merritt.