Today’s guest on ‘Friday Know Your Primate” has had more ink spilled in its’ name than any other primate I can think of…
Order Primates (primates)
Family Tarsiidae (tarsiers)
Genus Tarsius (tarsiers)
Species Tarsius bancanus (western tarsier)
Species Tarsius dianae (Diana tarsier)
Species Tarsius pumilus (pygmy tarsier)
Species Tarsius spectrum (spectral tarsier)
Species Tarsius syrichta (Philippine tarsier)
There are five species of tarsier (see above) all of which reside somewhere in Southeast Asia. They are nocturnal (and unlike other nocturnal primates they have a retinal fovea and lack the reflecting tapetum found in, say, lorises – which has lead some to argue that tarsiers where originally diurnal). They eat insects, arachnids and small vertebrates. They travel by means of verticla clinging and leaping – often leaping up to nine feet. They are all rather small, weighing between 120-140 grams.
One of the first things one notices in looking at tarsiers is the large eyes – each is larger than than animals brain, which has some interesting effects on the skull (makes it look more globular among other things).
Tarsiers share a number of traits in common with lemurs and lorises among them are: an unfused mandibular symphysis, high cusped molar teeth, grooming claws on their 2nd digits, multiple nipples and a bicornate uterus. On the other hand, Aiello (The relationships of the Tarsiiformes: a review of the case for the Haplorhini, in Major Topics in Primate and Human Evolution identified 23 traits tarsiers share in common with anthropoid primates. Amonf these are: the retinal fovea mentioned above, lack naked rhinarium, lack of sublingua, major blood supply of the brain comes from the promontory branch of the internal carotid, tympanic ring external to auditory bull and extends to form a bony tube and a sharp, deep low hafted skull. Additionally, tarsiers have some unique traits, such as a dental formula of 126.96.36.199/188.8.131.52, fused tibia and fibula, long legs and ankles and enormous hands and feet.
The above has led to several different interpretations of tarsier relationships to extent and exticnt primates. Not surprising – how do you classify something that has a bicornate uterus like lemurs and lorises and a hemichorial placenta like anthropoid primates? I don’t intend to talk about that in this post, but you can find an overview here
As always, here is a picture of the tarsier skeleton:
and here is one of the skull – showing the huge eye orbits: