Deathray 6

Here's an interesting thought. Let's pretend for a minute that representatives from 20 very different breeds of domestic dog in size and shape, were to be fossilized between their origin until whenever they may go extinct. Now fast foward 20 million years into the future. A civilization from another planet comes to Earth on a scientific expedition, part of which consists of trying to piece together the fossil record of this planet. They find everything we have, plus everything that'll get fossilized over the next few million years. What will they make of those dog skeletons. Since C. familiaris has numerous breeds of different sizes and shapes, would our hypothetical futuristic paleontologist class those somewhat different fossils as different species or as the actual one species they represent?

This leads me to my next point. Could it be possible that some similar fossils we find that exist contemporaneously with each other in similar geographic regions could be in the same species instead of different species. How do paleontologist tell if they if such two fossils are members of the same species or not?

MrDarwin

Yes, it's quite possible, although I might note that natural species generally don't show the degree of variation exhibited by domesticated dogs, because dogs have been bred specifically to be different from each other.

In fact, if chihuahuas and great danes were the only two living breeds of dogs, they would almost certainly be classified as different species--both because they are very different morphologically, and are physically incapable of interbreeding.

Albion

I'm not all that familiar with the way palaeontologists go about classifying fossils into species, but I do remember seeing papers such as the one where S. tchadensis was first reported, and the degree of detail in the measurements of the various aspects of the skull was quite impressive. I've seen creationists posting photos of skulls of different dog breeds (collie, pug, great dane, toy poodle, etc) and announcing that these would obviously be labelled as transitional fossils with an ancestor-descendant relationships if palaeontologists dug them up without knowing what they were.

I'm really not sure they would. Quite apart from the fact that the relative ages of the fossils would rule out that sort of relationship (and unlike creationists, palaeontologists do take radiometric dating seriously), the specialists are going to do a heck of a lot more than just eyeball the fossils the way creationists would. They'd notice the same number and configuration of teeth every time; they'd notice the same overall configuration of the brain case and the same sort of angle for the entry of the spinal column into the skull and similar relative measurements of distances and sizes and so on. I have a suspicion that a trained palaeontologist might not be nearly as impressed as the average YEC by the differences between wolfhound and peke skulls.

MrDarwin

On further reflection, there are some cases where the same species might be described more than once. The descriptions can be based on different parts of the animal, or fossils of the animal at different stages in its life, or fossils of a sexually dimorphic species. In these cases, a paleontologist would simply look for more complete fossils, or more fossils that bridge the gaps between the different fossils, that occur at or close to the same time.

It is also fairly common for plants to receive several different species (and even genus) names when different parts of the plant (roots, stems, reproductive organs, seeds) are not associated. In these cases, paleobotanists look for more complete fossils that show these different "species" to be connected in a single individual.