Named By: Herbert F. Standing - 1905.
Classification: Chordata, Mammalia, Primates, Strepsirrhini, Lemuriformes, Palaeopropithecidae.
Species: M. pithecoides, M. dolichobrachion, M. globiceps.
Size: Between 10 and 14 kilograms depending upon species - refer to main text.
Known locations: Across Madagascar, nut different species inhabited different areas - refer to main text.
Time period: Pleistocene to Holocene, as recently as 570-679 CE.
Fossil representation: Several skulls and now post cranial remains as well.
is currently the smallest of the known sloth lemurs although originally
it was thought to have been similar to today’s modern indriid
lemurs, an idea based upon comparison between the known skulls. In
1986 however, post cranial remains were found and attributed to
the genus and immediately the key feature of a forelimb much longer
than a rear limb was identified, something that indicated
Mesopropithecus was a sloth lemur. With this in
mind it’s possible
that Mesopropithecus might represent a more
primitive form of sloth
lemur that the more specialised genera evolved from. Even if this is
true however we do know that Mesopropithecus likely
other more specialised sloth lemurs until they all went extinct within
a few centuries of one another. This extinction is thought to have
been down to the combined effects of human hunting and habitat loss
through human activities.
Mesopropithecus has been classed as a sloth lemur because the forelimbs are proportionately longer than the rear limbs which indicate that Mesopropithecus relied upon these limbs to reach out and pull itself along branches. Indriid lemurs by contrast have longer hind limbs which they use to leap from branch to branch. Mesopropithecus however was a climber that would either walk across branches or hang from underneath them, an ability that was helped by skeletal adaptations that would allow it to travel this way. This more sedentary lifestyle would also require less energy than the more active indriids, which explains why Mesopropithecus and particularly some related sloth lemurs grew so large, since the energy it acquired from its food was used to sustain its body rather than move around. Mesopropithecus had a robust physique to deal with this size and weight to the point that it looks like a more heavily built indriid. This is why Mesopropithecus is considered to be somewhere in between since it’s too heavily built to be an indriid, while not as robust as other more specialised sloth lemurs.
There is some confusion regarding the lower jaw dental formula of Mesopropithecus (a problem shared by other sloth and indriid lemurs). One of the teeth is either an incisor or a canine although it is exceedingly difficult to make a clear distinction between the two types. This means that the lower jaw dental formula for Mesopropithecus is either 18.104.22.168 (one incisor, one canine, two premolars, three molars) or 22.214.171.124 (two incisors, no canines, 2 premolars, three molars). When combined with the upper dental formula of 126.96.36.199 however, both lower dental formulas add up to a total of thirty teeth in the mouth. The four frontal teeth are also arranged in a form of tooth comb as a feeding adaptation. Mesopropithecus is usually depicted as a folivore (an eater of leaves), but is also thought to have eaten fruits and seeds as well, the latter to the point of Mesopropithecus being described as a ‘seed predator’, an animal that makes special effort to eat seeds while often leaving other edible parts untouched.
There is obviously some variation between the remains of different Mesopropithecus species, but they can also be arranged by estimated weight and known geographical range of sub fossil remains. The table below provides a simple overview of this information.
|Species||Named by/Date||Weight in kilograms||Fossil distribution in Madagascar||Estimated extinction date|
|M. dolichobrachion||Simons et al. - 1995||14kg||Far North||570-679 CE|
|M. globiceps||Lamberton - 1936||11kg||Central areas||245-249 CE|
|M. pithecoides||Standing - 1905||10kg||South west||Unavailable|