Today we're going to talk about Tetrapodal Locomotion. Tetra-pods, which include all amphibians, birds, mammals, and reptiles generally use three different types of locomotion.

First we have plantigrade animals. This group, which includes humans, walks with the podials and the tarsals flat on the ground all at once. In other words, all of the bones of a plantigrade's animals foot touch the ground at one time when it walks. An advance of this is superior stability and weight bearing ability. This was the manner in which most early mammals got around. The other two types of locomotion we will be talking about today evolved from plantigrade.

Some of my favorite plantigrade animals include wolverines, skunks and bears. My least favorite plantigrade animal are opossums. Those guys are jerks. I also think opossums are raccoons are kind of creepy, and it's not just because they dig in my trash. Being plantigrade like humans they have kind of like a human-like walk. They have weird creepy little human hands.

Next we have digitigrade animals. These guys walk on just their finger and toe bones. They also have an elongated heel bone which, along with the Achilles tendon attaches to the back of the calf and creates a really fast spring like action. This allows digitigrade animals to move much more quickly and quietly than plantigrade animals. Some examples of digitigrade animals include kitties, and puppies, and kitties, and puppies, and some birds, but mostly kitties and puppies.

Finally we have unguligrade animals. Ungulids walk only on the tips of a few fingers or toes at a time. There are the even toed ungalids like deer, and pigs, and camels that walk only on two ro four toes at a time and then there are the odd toed ungalids like horses, and tapirs, and rhinos that walk on one or three toes at a time. By running on just the tips of their fingers and toes they spend less time pushing against the ground and therefore spend less energy. This allows them to run very efficiently over long distances, which is a very interesting thing to note if you consider that most ungalids are prey species running away from predatory digitigrade animals, like kitties.

So today we learned how tetra-pods get from here to there. I think it's really interesting to note through that just because animals might locomote in the same way doesn't necessarily mean that they're closely related. Hippos are actually more closely related to whales than they are to horses.

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