Past Behavior

September 14, 2011 · No Comments

Paleontologists study morphology - literally the study of shape. We find fossils, study their shape, and then make inferences about the shape of the entire creature, or use shape differences to figure out relationships between fossil organisms, or take the shape of bones and figure out the physics of the organism, or use shapes... well, you get the idea.

Shape, that is morphology, also helps us learn how the animals lived - their ecology, or in the case of fossils, their paleoecology. Animals don't live alone in boxes. They live in environments filled with elements they interact with - the rocks and shape of the land, water in the form of rivers and lakes, plants, and of course other animals. Ecologists studying modern animals talk about an animal's 'niche' - its place in nature. This includes answers to a number of questions:

·  How did it move? - Did it swim? Run? Move through the trees? Dig? Fly?!

·  What did it eat? - Plants? Leaves? Fruit? Bark? Other animals? Soft-bodied ones? Hard-shelled ones? Insects? Bones?

·  Was it eaten by other animals? - Did it protect itself? With poison? By running away?

·  How did it find mates? - Colorful displays? Bellowing calls? Smelly glands? Did it fight with others for mates?

·  How did it raise its young? - Lay eggs? Live birth? Leave them to fend for themselves? Dote over them?

The questions are endless, and really they are all getting at behavior. It's often said that behavior doesn't fossilize, but we can infer things about behavior from morphology.

As an example, let's say you find a fossil animal with an obviously broken leg bone which had healed. When bone heals (without proper setting like we humans do with modern medical technology) it grows irregularly, forming a bone scar over the injured site that can be seen on the fossil. This process takes a long time, and often the limb is unusable during this process. An animal with a healed injury probably couldn't take care of itself while healing, so how did it survive that ordeal? Perhaps other animals provided for it - bringing it food, protecting it from other animals. Was this a social group or a strictly familial gathering? We probably can't figure that out, but we do know the animal lived in a group. From a broken bone, we've figured out behavior. There are actual instances of this that have been reported in the literature (a few from the
La Brea tar pits that I've personally seen spring instantly to mind).

Description: Healed Florid Panther Bone

Healed bone of a modern Florida panther (from the Florida Museum of Natural History)

The recent featured article in the Journal of Vertebrate Paleontology is another great instance of using fossils to infer behavior. Jan Fischer and his colleagues have given us a little glimpse into the lives of sharks from 230 million years ago. They found fossil teeth and egg cases of fossils in freshwater deposites, miles from where there would have been any salt water. Also interesting, all the teeth are from juvenile sharks. Baby teeth and egg cases... The researchers figured that the best explanation for this collection was a nursery - a common place where sharks went to lay young. Now the question is, did the adults live in the freshwater too, or migrate there to have their offspring (much like many animals, especially fish, do)?

Description: Shark Reconstruction

Shark tooth and reconstruction from Fischer et al. (from the SVP website)

More fossils may answer the question, continuing the story of another great example of using fossils to infer behavior.

Tags: paleoecology · sharks

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Posted: 9/14/2011 1:35:21 PM by jhollandadmin | with 0 comments

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