Philippine tarsiers have gray fur and a nearly naked
tail. The middle finger is elongated. Head and body length are around 118-149 mm (4.6-5.5 in);
It weighs 113-142 grams (4-5 ounces)
The tarsier depends greatly upon vision than a good sense
of smell. The eyes are enormous. In volume, the capacity of the bony eye orbits (sockets) exceeds that of its brain case,
and larger than its stomach. Their eye sockets have post-orbital closure rather than the postorbital bar of the prosimians.
This feature keeps the eyeballs from being pressed against by the powerful temporal muscles to their sides .
The tarsier also has a very long tail ( 232
mm [9.1 in.] ), generally naked except for hair tufting at its end. The underside has dermal ridges like those found
on human hands and feet. Its tail is used for balancing like a tripod, and they prefer an erect posture at all times.
Like an owl, the tarsier has a joint between its skull
base and spine to allow head movement of a 180-degree arc . Its upper lip lacks a cleft yet it has musculature enabling it
to make faces. Adult Brain Weight: 4 g [0.2 oz]. Males are larger than females.
Tarsiers have sharp teeth, enabling them to catch their
prey easier. Unique among primates, tarsiers have only 2, rather than 4,incisors in their lower jaw. Their dental formula
is 18.104.22.168 22.214.171.124 x 2 = 34.
The name "tarsier/tarsius" is derived from the animal's
very long ankle bones. The tibia and fibula of the tarsiers are fused in their lower portions, acting as a shock absorber.
Considered a primitive trait normally seen in quadruped. Lower limbs are twice the length of its trunk. These enable them
to leap 3 meters (almost 10 feet) from tree to tree. Its movements are
similar to that of a frog.
Similarities to other Primates
Tarsiers share some characteristics of both the prosimians
and the anthropoids, while maintaining characteristics unique to themselves. Taxonomists have classified them as intermediate
between both groups and have assigned them to their own infraorder, which has just one living genus - Tarsius. Their relatives
in the fossil record are found going back to the Eocene epoch, from 54 to 36 million years ago.
Like many prosimians, they are nocturnal and have grooming
claws and bicornuate uterus.
Like anthropoids, they do not have a tapetum (a reflective
layer in their eyes).
In tarsiers, the internal structures of the nose and
ears and the blood supply to the brain and to a developing fetus are more like those of monkeys than of lorises. The monthly
sexual swellings of female tarsiers are also similar to those in anthropoids.