From 75-foot dinosaurs to saber-toothed tigers, an overwhelming number of animals stopped moving ages ago. But their remains are still talking.

At the American Museum of Natural History, scientists pore over nearly 5 million fossilized specimens across many different collections, looking back in time to piece together what these unique organisms looked like and how they behaved.

In celebration of National Fossil Day, marked today by the National Park Service and the American Geological Institute, dig into some of these fascinating specimens from the Museum’s fourth-floor Fossil Halls, highlighted below.

There’s new evidence that dinosaurs, once thought to resemble scaly lizards, were in fact fluffy, colorful animals. In the video below, Curator Mark Norell, who is chair of the Museum’s Division of Paleontology and studies important feathered dinosaurs from Liaoning, China, shares his thoughts on the significance of two new studies about fossilized feathers reported in the current issue of Science magazine.

If you missed the live Twitter chat with Dr. Mark Norell about fossilized feathers on Friday, Sept. 16, click here to read the discussion. Add your own comments using the hashtag#DinoFeathers.

It’s a story more than a century in the making. Barnum Brown’s extraordinary fossil-hunting career—which took him from a frontier farm to the world’s top fossil sites and to the halls of the American Museum of Natural History—included the discovery of the first complete skeleton of the Tyrannosaurus rex.

The priceless fossil—the one used to describe the carnivorous species now synonymous with “dinosaur”—was displayed in the Museum for more than 30 years beginning in 1906. Then the story took a twist, which is traced in a recent NPR piece “Bone To Pick: First T. Rex Skeleton, Complete At Last.”

They are some of the rarest of rare artifacts: fossil dinosaur eggs with the embryo still inside. And they are prized for what they can tell paleontologists about the adults that laid them.

The exhibition The World’s Largest Dinosaurs features a scale model of a nest found at Auca Mahuevo, Argentina, one of the largest known dinosaur nesting sites in the world. While it isn’t always possible to figure out which dinosaur laid a particular egg, in this case, an embryo within an egg found at Auca Mahuevo site allowed scientists to identify these eggs as those of titanosaurs, a group of sauropods that included such species as Ampelosaurus and Saltasaurus. Herds of female titanosaurs are thought to have laid the thousands of eggs — 15 to 40 at a time — in shallow nests dug out with their huge feet in dry mud and sand over miles of ground at Auca Mahuevo.

The results are in! We asked you to submit a nickname for Mamenchisaurus, the giant sauropod at the center of The World’s Largest Dinosaurs exhibition, currently on view at the Museum.

After hundreds of submissions and thousands of votes, the winner by a landslide is: Mame!

Runners up included Neckita—a nod to her extraordinary 30-foot neck, the longest relative to body size of any known dinosaur—and Mei Mei (“mei” means beauty in Chinese).