What is a lemur?!

 

Fig. 1: Primate taxonomy

Lemurs are primates, the order of mammals that also includes monkeys (like baboons), apes (like chimpanzees), and humans. Many people think lemurs don't look very 'primate-like', but they possess all the hallmarks that make a primate a primate, including: forward-facing eyes (Fig. 2), nails instead of claws, five digits on each hand/foot (Fig. 3), and a large brain for their body size.

 

Fig. 2: Forward-facing eyes of a blue-eyed black lemur at Oakland Zoo

 

Fig. 3: Lemur hands: Note nails (not claws), 5 fingers and opposable thumb for grasping

The order primates is divided into 2 suborders: strepsirrhini and haplorhini (Fig. 1). Strepsirrhini consists of lemurs and lorises, who share two very derived traits used for grooming: a set of projecting lower incisors and canines (called a dental comb; Fig. 4) and a grooming claw (Fig. 5) instead of a nail on the second toe. Lemurs and lorises do not possess more derived features shared by the haplorhini, including aspects of the placenta and inner ear. This is because lemurs and lorises diverged before the haplorhini evolved.

 

Fig. 4: Note the fused lower incisors--the dental comb used for grooming

 

Fig. 5: The grooming claw also used for grooming (nails on other digits).

You may have seen lemurs referred to as 'prosimians', but this is an outdated classification term that uses physical traits (i.e., looks) to group the primates that don't 'look very primate-like' (lemurs, lorises, tarsiers) together. In fact, tarsiers share derived traits with monkeys and apes, indicating they share a common ancestor after the lemurs and lorises branched off. Grouping animals together based on evolutionary relationships (cladistics; strepsirhini and haplorhini) rather than by 'looks' (gradistics; prosimians and anthropoid) results in taxonomy that represents the evolutionary history of the animals.

Today, there are 5 distinct families of lemur, all found on the island of Madagascar. They range in size from the mouse lemur (at 60 grams; Fig. 6) to the indri (at 10 kg; Fig. 7).

 

Fig 6: Mouse lemur feeding on flowers

 

Fig. 7: Indri

Lemurs are historically very popular zoo animals, due to their exotic look, yet docile nature.

Fig. 1 and further information can be found at http://johnhawks.net/explainer/primates/primate-cl... 

Fig. 2: Oakland zoo blue-eyed black lemur 

Fig. 3: Lemur hands 

Fig. 4: Dental comb 

Fig. 5: Grooming claw 

Fig. 6: Mouse lemur 

Fig. 7: Indri