BSCI392
8-29-07
Course introduction and basic issues

Paleontology: The scientific study of the fossil record.

This sounds simple, but a wide range of practical sub-disciplines and scientific objectives are covered in this definition including:

Yet when the public thinks of paleontology, they typically envision yet another discipline:

Paleobiological Reconstruction:

the hypothetical or speculative reconstruction of the life form and behavior of fossil organisms. This course is an investigation of the methods that paleobiologists use to develop and scientifically constrain these reconstructions.

It is no wonder that humans are fascinated by extinct animals. The past two decades have seen the discovery of such wonders as:

How do we attempt to understand these for what they are?

At a first-order approximation, paleobiologists use the comparative method - the comparison of extinct life forms to living ones to develop hypotheses of their life styles. Such comparisons take two kinds of similarity into account:

Structures that appear functionally analogous are our starting point for the development of hypotheses about life-style. E.G. numerous anatomical characters demonstrate that the extant timber wolf

and the extinct native North American dire wolf

They differ mostly in that the dire wolf's skull and teeth were more robust - a little closer to what one sees in spotted hyaenas or other bone-crushing animals.


Timber wolf

Dire wolf

Thus, we speculate that the dire wolf was generally similar to the timber wolf, but better adapted to bone crushing. Perceiving such similarities, like the perception of any pattern in a set of data, is a creative act. Ironically, of all paleontological methods, this one probably has the greatest tendency to push the limits of the proper Scientific Method. Humans are pattern-matching organisms and never short on imagination. What happens when we try to interpret the fossils of an animal with no obvious modern analog?


Parasaurolophus

A Cretaceous Period lambeosaurine ornithopod dinosaur. Like other ornithopods, it had a deep, laterally compressed torso and tail. The vertebral column of both was stiffened by ossified tendons. The comparison of the deep flat tail to those of swimming vertebrates, combined with the early 20th century conviction that large dinosaurs would have had trouble supporting their weight on land gave rise to reconstructions of Parasaurolophus as an aquatic creature. The idiosyncratic crest must have been a snorkel.

This was a falsifiable hypothesis. More thoughtful biomechanical analyses of the vertebral column showed that the trunk and tail were inflexible from side to side. Furthermore, the tail vertebrae of actual aquatic reptiles like crocodilians generally had long lateral extensions to give axial muscles better leverage.
Worse, although the crest connected to the pharynx and nasal cavity though an elaborate system of passages, no specimen of the "snorkel" actually had a hole in the top to admit air. Eventually a revised interpretation of Parasaurolophus as a land animal emerged.

Still, its crest stimulates speculation, including.

Interesting ideas, all based on analogy with living creatures, chosen to make two points: