New Fossil Finds Track When Armored Dinosaurs Spread Around the World #fossil #paleontology #fossils #dinosaur #fossils #dinosaurs #armoreddinosaurs

Paleontologists are just beginning to uncover the evolutionary backstory of armored dinosaurs like the ankylosaur Euoplocephalus. De Agostini via Getty Images

Smithsonian Magazine has a story about armored dinosaurs.  Recent discoveries are shedding light on the evolutionary history of the dinosaur group thyreophorans.  That group includes dinosaurs favorites like stegasaurs and ankylosaurs.

In popular depictions of paleontology, armored dinosaurs are often treated like icing on the Mesozoic cake. No Jurassic floodplain feels quite complete without a dinosaur like the spike-tailed Stegosaurus trundling around in the background somewhere. The same goes for Late Cretaceous forests, where the heavily-armored Ankylosaurus held a club-tipped tail capable of busting T. rex shins, if need be. We’ve known about such creatures for about as long as the word “dinosaur” has existed, but it’s only now that paleontologists are beginning to unravel the evolutionary epic of these armored marvels. In the past year, especially, paleontologists have described multiple new finds that outline how these armor-encased dinosaurs spread around the world in the early chapters of their history.

Both the spiky stegosaurs and the heavily-armored ankylosaurs belonged to a particular dinosaur group called thyreophorans. For decades, it seemed that stegosaurs were the banner bearers for armored dinosaurs only to go extinct in the early days of the Cretaceous—about 115 million years ago—and be replaced by the extensively-ornamented ankylosaurs. But discoveries in the past 30 years have dramatically altered that clean and neat story. In the Morrison Formation of the American west, for example, paleontologists have found that the famed Stegosaurus lived alongside an ankylosaur named Mymoorapelta. Not only did stegosaurs and ankylosaurs overlap in time, but paleontologists are discovering that these “living tanks” spread around the world much faster than anyone anticipated. Far from being dinosaurian sideshows, armored dinosaurs were evolutionary success stories.