Simons and Rumpler, 1988
Genus Eulemur (Eulemur mongoz 1) has an elongated muzzle with greatly reduced upper incisors. The first molar is clearly smaller than the second. They most often live in trees and they generally group in 5 to 6 bands of about 15 individuals. They emit a large variety of grunting vocalizations and calls of which certain high-pitched and loud ones can be given in unison by the whole group when they are disturbed. The young, usually single, holds itself onto the pelage of the mother right after birth and remains clung to her belly during her displacements.
The genus Eulemur was proposed by Haeckel, 1895 and used again by Simon and Rumpler to establish a taxon comparable to the old genus Lemur minus Lemur catta to separate Lemur catta due to its particular characteristics.
Since long, important differences in anatomy and behavior between Lemur catta and the other lemurids were noticed. Lemur catta can be recognized with a single glance by the clearly bright gray pelage, the black and white face and the ringed tail. They also differ by the presence of brachial and antebrachial glands, with a keratinized differentiation at the forearms and by the cranial characters (Petter, 1962; Petter et al., 1977).
Research at Duke, on the behavioral field and at Strasbourg, on the cytogenetic field, has drawn attention to the much larger difference than was formerly supposed to exist between Lemur catta and the species historically placed close to it and the high resemblance of Lemur catta with Hapalemur (Simons and Rumpler, 1988).
The cytogenetic studies permitted a reconstruction of an ancestral karyotype of the Lemuridae and to propose a phylogenetic tree of their chromosomal evolution (Rumpler and Dutrillaux, 1986).
An ancestral intermediate karyotype divides the tree into two trunks (cladogram Dutrillaux & Rumpler). One leads to the Eulemur group and is characterized by fusion of the ancestral chromosomes 1 and 11, which give birth to a metacentric chromosome characteristic for all 'Lemur', except Lemur catta. The other leads to Lemur catta. Hapalemur is characterized by fusion of the chromosomes 1 and 3, which give birth to another metacentric chromosome modified by new intrachromosomal rearrangements. These results ground arguments to separate Lemur catta from the 'Lemur' group, but, as Lemur catta was the type of 'Lemur', a new genus should be created and the term Eulemur, already used by Haeckel and being synonymous with the genus 'Lemur', was chosen.
-The systematics of the genus Eulemur (former genus Lemur minus Lemur catta) brought a lot of controversies, because certain forms were described from damaged museum specimens or by ignorance of the existing color differences between the sexes. This classification was based on morphology, some cranial characters, pelage color, geographic distribution and etho-ecology. The distinctive characters were often missing, and the distinction between certain forms was very delicate.
Not long ago, when the forest was covering the better part of Madagascar, it was possible to differentiate in the East and in the West, from North to South, a series of subspecies in process of differentation, differing from each other by minimum characters and corresponding to populations partially isolated by geographic relief or by rivers (illustrated by Milne-Edwards and Grandidier). The water flows often formed almost impassable barriers because of the large number of crocodiles.
Many of those transitional forms probably have disappeared, but some might still exist and the inventory of those types might perhaps not be finished.
Facing the difficulties to characterize with sufficient precision the different forms of this radiative evolution, it is unthinkable, certainly for this genus, not to take into account other data and especially those brought to light by cytogenetics and molecular biology associated with hybridization experiences.
These studies permitted to differentiate seven species in the genus Eulemur. All these Eulemur are however of comparable shape. In times past, it were the most numerous lemurs in the forests. Their size is comparable with the size of a cat, with a head-and-body length of ± 50 cm, tail length of ± 60 cm and average weight of three kg. The pelage is dense. They live in troops, which can consist of up to 20 individuals. They run and jump with agility. This genus is occurring in most forests of Madagascar.