Tag Archives | cladistics

Why are Birds Dinosaurs?

nationalgeographic.com

Month after month, one of the most popular posts on the Paleocave blog is the How to Read a Cladogram post I did some time ago. I always intended to follow it up with more cladistic fun. So, hold onto your butts, we’re going to let the dinosaurs loose.

Birds are dinosaurs. We’ve all heard this. But does that phrase make any sense? Not really. Dinosaurs, for the most part, are things that were really big, were mostly scaly, had fantastic teeth, and are extinct. Birds, on the other hand, don’t have teeth, are generally small, and are covered in feathers (I know that you know that lots of old school dinosaurs had feathers too, but whatever). So, why do we say that birds are dinosaurs? The answer involves evolution and the meaning of taxonomic names in biology.

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Diagraming Evolution, or How to read a Cladogram

Remember the Linnaean system of classification you probably learned in grade school or high school (heck, maybe even college)? It went something like this…

Kingdom -> Phylum -> Class -> Order -> Family -> Genus-> Species

Linnaeus started using this classification system in the 1700s and he had a good run; we still use his system in certain situations. However, we’ve moved away from this ranking system mostly because of the discovery of transitional fossils that screwed with Linnaeus’s idea of neat little boxes for all of life to be categorized into. This system falls apart, for example when you have two equivalent ranks, let’s say class Osteichtyes (boney fish) and class Amphibia (amphibians), and find a transition between the two.

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