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Ganlea megacanina: Saki of the Eocene
July 2, 2009Posted by on
Meet the White-faced Saki, Pithecia pithecia. P. pithecia lives in South America, where it scampers about the low canopy eating the seeds of fruit with tough outer shells. To get through those tough outer shells, it has robust, stout canines that are able to pierce the skins and dig out the soft fruit and seeds inside.
Now let’s jump back in time to the Eocene, and across space to Southeastern Asia. Here, we’ll find a group of primates that we would probably recognize as monkeys. These are the Amphipithecidae. One of those early monkeys would be Ganlea megacanina, a new fossil primate described by Chris Beard and colleagues in the latest issue of the Proceedings of the Royal Society B. G. megacanina was found in the Pondaung Formation in Burma, and is known only from teeth and a little bit of jaw.
I can’t tell you exactly what G. megacanina looked like because we don’t have most of that information. This is typical for primate paleontology (which was what made Darwinius such an exciting discovery). But, we can enjoy a few brief glimpses of what it may have eaten and how it may have behaved.
G. megacanina has, as its name would imply, a massive canine tooth. The authors looked at the canine:molar ratio and determined that the individual was a male, but also found that the tooth is bigger than would be expected simply by being a male in a sexually dimorphic species. They also observed that the apex, or tip, of the tooth was worn almost flat. This type of wear is most likely dietary, as the wear pattern that results from simply closing your moth and having your teeth rub against each other is usually more oblique than the wear patterns present here. Based on the anatomy of this canine tooth, it is a pretty good inference to make that these primates were eating a diet very similar to modern sakis: soft fruit and seeds covered by a tough outer husk.
We can also tell a bit about this guy’s relationships to other primates. Together with two other primates from the Eocene of Burma, he is part of the Amphipithecinae subfamily of Amphipithecidae. We group them together based on the anatomy of their premolars, which are shortened mesiodistally (which means from the front of the mouth to the back) so much so that they are actually wider bucco-lingually (on the cheek-tongue “axis”). This feature, along with several features of the cusps of the teeth, ally the entire group more closely with anthropoid primates- specifically either modern Platyrrhines or the extinct Propliopithecids- than with adapiforms. This analysis puts this group of primates close to being some of the first monkeys. It looks as though they are a bit more evolved in the anthropoid direction than Beard’s famous Eosimias, or Dawn Monkey, though, so they are not quite at the root of our clade.
Beard, K., Marivaux, L., Chaimanee, Y., Jaeger, J., Marandat, B., Tafforeau, P., Soe, A., Tun, S., & Kyaw, A. (2009). A new primate from the Eocene Pondaung Formation of Myanmar and the monophyly of Burmese amphipithecids Proceedings of the Royal Society B: Biological Sciences DOI: 10.1098/rspb.2009.0836