Thursday, August 16, 2012

Animals Then and Now: Choose Your Weapon

This week I'm going to go back into my comfort zone of comparing extinct dinosaurs to modern animals in order to better understand them.  Specifically, I would like to talk about animal weaponry.  Many animals, alive and extinct, have weapons to either help defend themselves from being eaten or to help them catch/kill other animals for themselves to eat.  At work I get to see some of these dangerous animals up close (sometimes too close!).

Dangerously Cute!!!  (Baby Arctic Foxes)

If you notice, predatory animals tend to all have similar weapons to help them catch their prey regardless of whether or not they are related to each other.  This is because the ultimate goal of every predator is the same: catch the prey.  Check out this claw from an African Lion.

African Lion front claw (cast)

See its shape?  Its hooked.  Hooks are great for catching things.  They are sharp at the tip to pierce the skin of whatever they are hunting and they are curved to prevent whatever they are catching from pulling away.  Even us humans use hooks to catch fish.  Its a simple yet highly effective design.  It isn't designated to claws either.  Predatory animals that can't use claws many times use teeth instead like snakes.

Now check out THIS weapon.

Allosaurus hand claw (cast)

Same structure as the lion just a lot bigger right?  Its from an animal not remotely related to lions though.  That's a hand claw from an Allosaurus.  Even though Allosaurus and African Lions don't share much in common when it comes to their DNA.  They have many of the same adaptations thanks to convergent evolution (which I talked about in my very first post!).  So what does this tell us about dinosaurs like Allosaurus?  Well, a lion will use its hooked claws to hold on to struggling prey that is many times larger than the lion itself.  It can be safe to assume that Allosaurus was doing something similar with its claws.  Since Allosaurus was much larger than a lion and its claws were also much larger than a lion's, it makes sense that it could have been hunting animals that were also much larger like the myriad of other dinosaurs it shared its habitat with during the Jurassic.  


Extinct predators that didn't really have dangerous claws (or any claws) would have used other things.  Check out Tyrannosaurus rex.  Tiny arms, HUGE head with teeth...that are curved!  Not really related to snakes that closely but similar adaptations none the less.

Tyrannosaurus rex

Not all predatory weapons HAVE to be hooks either.  As long as they catch prey they are successful.  Crocodillians don't really have curved teeth but they do have powerful jaws that do a good job of locking down on prey hard enough so that it can't escape.  Many turtles and fish create a vacuum under the water to suck prey into their mouths.  Amphibians don't have much in the way of teeth and absolutely nothing when it comes to claws yet they are highly effective predators in their own right thanks to their sticky tongues and fast mouths.

With a tongue like this Palm Salamander's who needs teeth?

What about the prey?  They certainly aren't interested in catching any other animals.  The weapons they DO have are usually designed to keep predators as far away as possible.  Think about an animal like a porcupine.  They have many sharp quills coming out from their backs.  Most predators have to deal with the dilemma of working around those things which requires them to keep a distance between the two of them.  Not an easy prey animal.  Other animals have things like armor on their hides like armadillos and tortoises to discourage predators from attacking.  How about dinosaur weapons?  Here is a tail spike from a Stegosaurus.

Stegosaurus tail spike (cast)

Its sharp.  But it isn't curved or hooked.  Without ever seeing the animal alive I can guess that it's first line of defense against something like Allosaurus would be to keep the predator away and discourage it from attacking in the first place.  If it HAD to stab with the spikes, they could easily be removed after the damage is done because they are straight.  The last thing a prey animal wants to do is hold on to its attacker!


Works Cited

Holtz, Thomas R., and Luis V. Rey. Dinosaurs: The Most Complete, Up-to-date Encyclopedia for Dinosaur Lovers of All Ages. New York: Random House, 2007. Print.

McGhee, G.R. (2011). Convergent Evolution: Limited Forms Most Beautiful. Vienna Series in Theoretical Biology, Massachusetts Institute of Technology Press, Cambridge (MA). 322 pp.

Sabuda, Robert, and Matthew Reinhart. Dinosauria. Kbh.: Carlsen, 2007. Print.

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