Transitional series

I'm often asked about what I think of "transitional fossils". Here's the thing: it's a red herring. Not because we can't see important transitions everywhere in the fossil record, but because a single fossil can't show a transition by definition. If you want to see a transition you need a series of related animals, generally organized by who is related to whom.

I've taken one of the series I use for teaching and public speaking and turned it into an animated gif for you here. I realize there aren't any names on this version - I'll post a non-animated version with labels next week. In the meantime I think it shows off the more important concept: how easy it is to look at two very different structures and feel like they are insurmountably different up until you fill in other fossil relatives.

We'll return to our regularly scheduled anatomy and giant sauropod posts soon! 

Animated transitional series of theropod shoulders on the way to birds.