June 7th

What is–and is not–a dinosaur?

Want to avoid the ire and swift corrections of a fervent dinophile? One of the first and most common ways to get a conversation off on the wrong foot is to confuse dinosaurs with other prehistoric creatures. It may not seem terribly important to most people, but getting the nomenclature right is one of the easiest ways to show you have an understanding of the prehistoric world. Need some help distinguishing dinosaurs from non-dinosaurs? We’re here to help.

No matter how many blog posts and soapbox-style rants appear on this issue, the general public has–for the most part–never been taught to distinguish a dinosaur from any other extinct animal. We’re not here to point fingers. We just want to clear up some mis-conceptions.

Firstly, dinosaurs are a very special group of animals that arose in the Triassic period, and, with the exception of modern birds, went extinct at the end of the Cretaceous period–some 160 million years. Dinosaurs are separated from other kinds of animals by several distinct anatomical criteria–adaptations, chiefly, of the limbs and the feet. Dinosaurs walked with their legs directly under their bodies, unlike reptiles which trudge through life with a sprawling posture.

Because dinosaurs are defined scientifically by their characteristic limbs, we cannot call a pterosaur a “flying dinosaur.” It is an altogether different sort of creature. Nor can we confuse sea dragons like ichthyosaurs, plesiosaurs, or mosasaurs as dinosaurs. The limbs of these animals have all been modified and are not direct descendants of dinosaurs. They are evolutionary cousins.

Mammoths and other prehistoric mammals are also not dinosaurs. Neither are pelycosaurs like the sail-backed Dimetrodon.

When in doubt, look for museum labels and online assistance to determine what you’re seeing. Understand the repercussions of how an animal is classified and what those distinctions mean.

Need help deciding whether an animal is a dinosaur or not? Ask us on Facebook and Twitter using the hashtag #TDIDinos.