Sunday, July 4, 2010

An Island Arrival: Lemurs Part I

Over the last couple of days I have been delving into the world of one of the weirdest groups of mammals, the lemurs. Lemurs are usually mistaken for monkeys when people first see them, although I am not exactly sure why since I really only see similarity in their hands and feet, which both have opposable thumbs/toes. I mean, they have long snouts, furry ears and whiskers. They basically look like cats with fingers, especially when you consider some species even purr and meow like a cat. Don't get me wrong though, lemurs are relatives of monkeys and apes, but are a very distinct group from our simian friends.
The most important distinction is their wet nose. This is because primates are split in to two groups, the ones with wet noses and the ones with dry noses, and lemurs certainly fall in the wet nose category. A wet nose is very important to them too, because unlike the dry-nosed monkeys who communicate visually, lemurs use smell to give signals to each other...which is another similarity to cats. O_o The other features of lemurs are their interesting grooming devices (sounds kinky for some reason). The lower incisors of lemurs form what is called a toothcomb, which is exactly what it sounds like; a comb made from teeth. It is used to help groom the fur and is only found in lemurs. The other grooming device of lemurs is their claw. Four of the lemur's toes have nails on them, but the second toe has a large claw on it which is officially known as the "toilet-claw". I know, I laughed when I first heard it too. It is called this because when it was first named the term toilet meant "personal grooming", not the...can. Anywho, the toilet-claw is primarily used for raking through the fur, usually in places the lemur cannot reach with its toothcomb. The only lemur without a definitive toilet-claw or tooth comb is the aye-aye, which is not suprising considering how damn weird it was anyway. I mean, look at this thing! I'm going to go into a little detail on aye-ayes just to explain how strange they are. Aye-Ayes are commonly called "primate woodpeckers" because they are adapted to breaking in to tree trunks and extracting yummy beetle grubs. They do this first by tapping on the bark with their creepy, skeleton-like fingers and listening with their big-ass ears to see if their is a hollow spot in the tree. When they find it they use their chisel teeth and rip through the bark then shove their ridiculously long middle finger into the hollowed cavity to extract some nice delicious larvae.
Anywho, seeing as this is supposed to be about prehistoric animals let's move on to the extinct forms of lemurs. Lemurs evolved about 55 million years ago (although some studies suggest about 10 million years earlier) which was right after the dinosaurs went extinct when the world was on the rebound from all of that death and destruction. The fossil record of early lemurs is somewhat crappy, mostly due to rocks of this time are rare in Madagascar (where all lemurs are found today) and Africa (where lemurs originated).
One big problem in lemur prehistory is exactly how they reached Madagascar. The island broke off from Africa about 160 million years ago, which is waaaay before the first lemur appeared on Earth. This means that they sure as heck did not evolve there, especially when you consider the earliest lemur fossils are known from Africa.
So how did these tiny primates get across 560 kilometers of water? It is generally thought that they took a boat. No, really. They did. Most scientists believe that lemurs hitched rides on rafts of matted plants and sailed across the Mozambique Channel to their lovely island home. For most mammals this would be a nearly impossible task, but some species of lemur (which are also among the most primitive) have the ability to lower their metabolism in a manner similar to hibernation. This means they could have napped the entire trip and landed on the island safe and sound. This whole process likely took place about 40 million years ago (although, once again, other scientists say otherwise and suggest an earlier arrival of 60 million years ago).
After reaching Madagascar lemurs found themselves in a perfect world, with literally thousands of niches to fill. The first group of lemurs to split off from the main family was the group that eventually lead to our messed up friend, the aye-aye. This was pretty much as soon as the ancestral species reached the island.
Yes, I can picture it now. The wacky cousin proto-lemur gets off the boat and starts scratching and gnawing at the bark to eat the beetle grubs while the rest of the family just is glad to get rid of him. XD
Anywho, this is only part one of my little adventure into the history of lemurs. Next up will be stuff on the lemurs diversification following their arrival on Madagascar!

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