How Birds and Reptiles are Related
Here at the zoo, we specialize in reptiles and amphibians, and that includes exhibits with emus and parakeets. Because of this, we often hear feedback from visitors wondering why on earth we have birds at a reptile zoo. Well, the short answer is…birds are now classified as reptiles! However, that wasn’t always the case.
There are four major groups of reptiles living today: turtles and tortoises, lizards and snakes, crocodilians, and dinosaurs. The last two groups are archosaurs, a very specialized group of reptiles that have been around for 225 million years!
The Missing Link
For centuries, many scientists hypothesized that birds were reptiles due to similarities in their anatomy, but there was no hard fossil evidence to support it. Then, in 1860, archaeologists discovered a fossil of a highly detailed Archaropteryx lithographica (a bird-like dinosaur), which filled the void of the “transitional species” that scientists needed to link birds and reptiles. Since then, many fossils of feathered dinosaurs have been found.
Similarities and Differences
Theropod dinosaurs share over 100 traits with modern birds. For example:
- Three forward-facing toes
- Fused collarbone, called a wishbone (yes, that kind of wishbone!)
- Hollow bones
Of course, not all theropod dinosaurs could fly—can you imagine a flying T-rex?! Some dinosaurs didn’t have the right skeletal adaptations or their feathers were rudimentary. It is thought that feathers were originally used for mating displays. Modern birds still use them for that reason.
66 million years ago, the fifth mass extinction event in earth’s history happened when an asteroid hit our planet, causing rapid global events like tsunamis and volcanic eruptions. When resources became scarce, larger animals were at a disadvantage, so all non-avian dinosaurs died. Ultimately, the need to adapt to a changing environment drove the evolution of birds and made them successful. Today, there are between 9,000 and 10,000 species of birds!