Saturday, November 07, 2009

Them Bones

Skulls are fascinating. Though I didn't always know that. Previous to my current understanding, skulls were evidence of a story - survival, starvation, struggle, etc. Interesting to look at, to be sure. But never did I appreciate the minor details that distinguish one skull from another until a few weeks ago.

With a minor prod from a park visitor, who also happened to be mammal biologist, I began studying the few skulls in the park collection. And I was amazed.

The dental formula of each mammal helps to distinguish one family and often one species from another. It's really quite interesting.

And there is one dental formula that is unmistakable. I found it quite fascinating. You might not share my enthusiasm, but I am going to share it with you anyway.

I've got two skulls below to compare to.

A coyote skull

A bobcat skull

Okay. Let's look at the coyote first.

The bottom half of the jaw, starting from the middle front and working back along one side, has 3 incisors, 1 canine, 4 premolars, and 3 molars (this guy is missing his last molar on the left hand side).

The top half of the jaw, also starting from the front middle and working back along one side, has 3 incisors, 1 canine, 4 premolars, and 2 molars.

In skull language, the number and type of teeth is written like this: I 3/3 (meaning 3 incisors on top, 3 incisors on bottom), C 1/1, P 4/4, M 3/2 x 2 = 42.

So if you take a close look at the premolars and the molars, you can see that the premolars are sharp, meant for cutting meat. But coyotes, and other canines sometimes eat other things as well, so their molars help them grind those other foods, so they are wider, and have more cusps (the little pointed parts of the tooth).

Okay, how fun was that?

Now let's look at the bobcat.

The bobcat has far fewer teeth than the coyote. The bottom half has 3 incisors, 1 canine, 2 premolars and 1 molar.

The top half has 3 incisors, 1 canine, 2 premolars and 1 molar just like the top half. Now, wait, you say. I don't see the molar. Just the 2 premolars. That's what I thought as well.

But take a closer look.

See that tiny little smidgen of a tooth back behind the 2nd premolar? At first I thought it was just a funky part of the premolar. But nope. That is the molar. It is almost non-existent. And that one little molar up top there is very diagnostic of cats. All cats, from kitty cats to massive lions and tigers, have that one, small molar.

When I learned that, I wanted to go and pry open the mouth of my little kitty. But it just so happened that he had to take a little vet visit not too long after that. So when the vet opened his mouth, I took a look to see if I could see that little molar. And sure enough, there is was. So small. Almost not there. But it was there.

Now all you cat owners, you're going to do the same thing, and harass your cat to pry open it's mouth, aren't you. If you do, let me know if you can see it.


Felicia said...

That's very cool! But it raises the question of WHY all cats have that tiny little molar remnant—was it bigger in earlier iterations of the species? What does it do for the animal now?

Interesting stories always raise yet more questions!

Sparverius said...

Felicia, those were my thoughts as well. And I imagine in some future time, that molar will be long gone. No use for it now, why keep it around.

Jenny said...

Very cool. So many things to study in this world, isn't it great? The more we learn, the more avenues open up and ask to be explored.

deejbrown said...

Well, damn if it isn't there. This was an interesting and incisive (oops) post!