Mesopropithecus
Name:
Mesopropithecus.
Phonetic: Me-sp-pro-pif-e-cus.
Named By: Herbert F. Standing - 1905.
Synonyms: Neopropithecus.
Classification: Chordata, Mammalia, Primates,
Strepsirrhini, Lemuriformes, Palaeopropithecidae.
Species: M. pithecoides, M.
dolichobrachion, M. globiceps.
Diet: Herbivore.
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.
Mesopropithecus 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 lived alongside 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 1.1.2.3 (one incisor,
one canine, two
premolars, three molars) or 2.0.2.3 (two incisors, no
canines, 2 premolars, three molars). When combined with the
upper dental formula of 2.1.2.3 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 |
Other known sloth lemurs include Palaeopropithecus, Archaeoindris and Babakotia, the latter one thought to be closest to Mesopropithecus while the first two are considerably bigger.
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