Today’s Factismal: The oldest known bird dates back 135 million years ago – or does it?
One of the open secrets in science is that there are very few cases where you can say definitely categorize something. For example, what you call a “cloudy day” might not seem very cloudy at all to someone raised in foggy San Francisco. And it is very hard to tell where the estuary ends and the ocean begins. But those are clear-cut examples when compared to the definition of species and deciding when a new species starts and an old one ends.
Right now, an argument over when the birds split off from the dinosaurs is raging in the paleontological community. On the one side are those who say that Archaeopteryx lithographica (“Ancient wing written in stone”) and the recently-discovered Aurornis xui (“Xu Xing’s Dawn bird”) are early birds (that did indeed eat worms, among other things). And on the other are those, including Xu Xing, who say that they are merely bird-like dinosaurs and not true birds at all. As usual, the argument is based on slightly different definitions of what a “true bird” is (can you create a definition that covers the cassowary and the wren?) and careful measurements of the fossils.
If that sounds like your cup of tea, then you are in luck. The Open Dinosaur Project is looking for people to measure the limbs of dinosaurs in an attempt to better define the various dinosaur groups. Though they have finished the first set of measurements, if enough people show interest, they may start on the second!