Videos

[MUSIC]

[Visitors to the Museum look at an evolutionary tree for dinosaurs, with dinosaur models at the end of each “branch”.]

NARRATOR: What are the different types of dinosaurs, and how are they related to each other? 

[The logo for the American Museum of Natural History appears on top of the previous footage. The scene changes to a Triceratops fossil on display.] 

NARRATOR: There are three big groups– 

[Visitors pass by an Allosaurus fossil on display.]

NARRATOR: –in the dinosaur family tree, each containing popular dinosaurs–

[Visitors pass beneath a towering fossil display of an Apatosaurus.] 

NARRATOR: –you might know. 

[The footage of the Museum halls is replaced by an animated graphic. First, the text “Ornithischians” appears, with images of a Triceratops fossil, a model of an ankylosaur, and a Stegosaurus fossil.]

ROGER BENSON (Curator, Division of Paleontology): There are ornithischian dinosaurs, like Triceratops or Ankylosaurus or Stegosaurus.

[This graphic slides to the left and is replaced with text, reading “Sauropodomorph” and images of an illustration of a Diplodocus and a fossil display of Apatosaurus.] 

BENSON: The sauropodomorph dinosaurs, like Diplodocus, or Apatosaurus,

[This graphic slides to the left, but the text “Sauropodomorph” remains on the screen. Images of a Plateosaurus fossil and an illustration of Massospondylus appear.] 

BENSON: –alongside their close relatives like Massospondylus or Plateosaurus. 

[This graphic slides to the left and is replaced with text, reading “Theropod” and images of a fossil T. rex  and Velociraptor appear alongside an illustration of Coelophysis and footage of an owl.] 

BENSON: And the third group of dinosaurs are the theropod dinosaurs. They include all living birds. And things like Tyrannosaurus rex, Velociraptor, and Coelophysis.

[BENSON appears on screen speaking to the camera. Text reads: “Roger Benson, Macaulay Curator, Division of Paleontology”.]

BENSON: It’s likely that theropods and sauropodomorphs are related to each other, and that ornithischians are just outside of those. But paleontologists aren’t 100% confident about this. And other relationships have been proposed.

[An animation of an evolutionary tree appears. At the bottom where all the lines originate, text reads: “Common Dinosaur Ancestor.” The lines split and to the left, an illustrated Triceratops appears with the text “Ornithischians” beneath it. To the right, the line splits once again to show “Sauropodomorphs” with an illustration of a titanosaur on the left, and “Theropods” with an illustration of a Deinonychus to the right.]

NARRATOR: But for now, we’ll go with the current thinking that theropods and sauropodomorphs are more closely related, 

[The Sauropodomorphs and Theropod text and illustrations turn green and new text appears above them: “Saurisichians”.] 

NARRATOR: –in a group known as Saurischians.

[The “Saurischians” text disappears and a new bracket covers all three groups and text, lumping them together. New text appears below the bracket: “Dinosauria.”]

NARRATOR: All of these groups sit under one umbrella, the group Dinosauria. 

[BENSON reappears on screen.] 

BENSON: And that group is recognized based on the fact that all dinosaurs share particular features of their skeletons,

[Video of different angles of an Apatosaurus fossil on display in the Museum’s halls, showing its hind limbs.] 

BENSON: mainly related to the hind limb and the pelvis, and they’re the kind of anatomical features that you’d expect in animals– 

[BENSON reappears on screen.] 

BENSON: –that hold their legs directly under their bodies and have legs–

[Video of the hind limbs of the Apatosaurus fossil on display, showing that the legs are mostly right under its body.]

BENSON: –that are more or less vertical

[Footage of a lizard shows its back legs are sprawled to the side, mostly next to its body instead of beneath it.] 

BENSON: –rather than sprawled out to the side. 

[Side-by-side footage shows the femurs of a dinosaur and a non-dinosaur reptile. A line traces the curves of each, with the dinosaur femur jutting out in a traditional “ball-and-socket” type joint, whereas the reptile femur only juts out a little and is much more smooth.]

BENSON: The thigh bone in dinosaurs has a straight shaft, but then a head that turns into meet the hip socket.

[Footage of the hip and hind limbs of a Tyrannosaurs rex fossil on display at the Museum. The hole in the hip socket is filled in with green to highlight it.] 

BENSON: And the hip socket itself has a hole that goes through the center, 

[A line traces over a flare of bone above the hole in the hip of this fossil.]

BENSON: –but a large buttress that runs over the top– 

[An Allosaurus hip is shown, and a green line traces over the same flare of bone on its hips.] 

BENSON: –to support the pelvis on top of the hind limb against the forces of gravity. 

[Side-by-side footage of a Patagotitan’s legs and a Tyrannosaurus’s legs show them to be very upright, and below their bodies.] 

NARRATOR: This combination leads to dinosaurs holding their legs vertically under their hips 

[Footage of a reptile fossil shows its hind limbs, which are so sprawled to the side that they mostly touch the ground even on the sides.] 

NARRATOR: –unlike other reptiles of today and the past. 

[Footage of a Komodo dragon walking head-on towards its prey.] 

NARRATOR: Watch how this Komodo dragon walks. 

[The video pauses, and a dashed line draws on top of its front leg, going out to the side from its joint, then angling down to the ground.]

NARRATOR: Its legs go out to the side from its joints, rather than beneath it, 

[Footage of an ostrich walking pauses to draw on a dashed line, going straight down to the ground from the ostrich’s hip, without sprawling to the side first.] 

NARRATOR: –not like this ostrich, a living dinosaur. This might seem like quibbling, or nitpicking,

[Footage of a bearded dragon lizard appears next to footage of a bird of prey–the former’s legs sprawl out to the side, and the latter’s legs are directly beneath it.]

NARRATOR: –but differences like these don’t arise overnight–they take millions of years to evolve.

[Footage of an Allosaurus fossil appears next to the skeleton of a Komodo dragon.]

NARRATOR: So when scientists see consistent differences in skeletons between two groups, they can be sure that those differences reflect real evolutionary changes.

[BENSON reappears on screen.]

BENSON: We try to understand the relationships among different dinosaur species by studying their anatomy. And we expect that animals that are more closely related to each other will share more features, whereas animals that are more distantly related to each other will share less features.

[Three illustrated dinosaurs appear on screen, with accompanying text below them: a Triceratops with text “Ornithischians,” a titanosaur with text “Sauropodomorphs,” and a Deinonychus with text “Theropods.”] 

NARRATOR: We can see this play out in the three major groups of dinosaurs.

[The text “Ornithischians” moves to the bottom center of the screen, and all other illustrations and text disappear. Footage of a hadrosaurid hip appears.]

NARRATOR: The ornithischian dinosaurs have the same hip bones as all dinosaurs, 

[The footage disappears and two illustrated hip bones appear on screen. The left has text beneath it that reads “Ornithischians” and the right has text that reads “Saurischians”.] 

NARRATOR: –but one bone points in a different direction–

[Both of the hip illustrations are made out of what seems like three big pieces of bone. In both illustrations, the rightmost bone is highlighted, and in the Ornithischians the bone is oriented towards the left, and in the Saurischians the bone is oriented towards the right.] 

NARRATOR: –than that of the theropods and sauropodomorphs. 

[The illustrations disappear and are replaced with footage of a towering Barosaurus fossil at the Museum, with text beneath it that says “Sauropodomorphs.”] 

NARRATOR: The sauropodomorphs differ from ornithischians and theropods by– 

[The footage changes to a video panning from the head of an Apatosaurus along its long neck.]

NARRATOR: –all having small heads and long necks relative to their overall bodies.

[This footage disappears and is replaced by side-by-side footage showing the three big toes on a Tyrannosaurus fossil, and the two hind limbs of a different theropod fossil.]

NARRATOR: And the theropod dinosaurs all walked on three toes and two legs, instead of four,

[These side-by-side images disappear and are replaced with footage of a single theropod tooth, with serrated edges, followed by a shot of a full mouth of teeth in a Tyrannosaurus fossil skull.] 

NARRATOR: and most had blade-like teeth that made them excellent predators.

[BENSON reappears on screen.]

BENSON: It’s common for people to use the word dinosaur to refer to any extinct reptiles. But dinosaurs aren’t just any extinct reptiles, they’re a specific group of extinct animals whose only living representatives are birds. There were a few things that dinosaurs never did.

[Footage of penguins diving and swimming in water, surrounded by ice floes.]

BENSON: Outside of birds like penguins, they never evolved to live in the oceans.

[A painted illustration of a mosasaur attacking two fish appears. Text points to the mosasaur and labels: “mosasaur, not a dinosaur.”]

BENSON: So if you’re looking at a giant extinct reptile that lived in the oceans– 

[Footage of a plesiosaur fossil with a long neck is labelled with text: “plesiosaur, not a dinosaur.”] 

BENSON: –like a plesiosaur or an ichthyosaur, then you can say that’s not a dinosaur. 

[BENSON reappears on screen.] 

BENSON: Other things that are commonly mistaken for dinosaurs, include the flying reptiles, the pterosaurs. 

[A pterosaur fossil is displayed as if it is soaring through a Museum hall.] 

BENSON: Now, they’re not dinosaurs, but they’re actually quite closely related 

[An illustration of a pterosaur is labelled with text: “pterosaur, not a dinosaur.”]

BENSON: –and they share a handful of features with birds and dinosaurs.

[BENSON reappears on screen.] 

BENSON: Interestingly, they independently evolved flight. So although they fly, 

[Another pterosaur fossil in a Museum hall appears, with wings outstretched.]

BENSON: –they’re not related to birds, which are the flying dinosaurs.

[The Museum’s Hall of Primitive Mammals appears, with several fossils standing next to each other, collected on a platform on display. Text labels them: “mammals & ancestors, not dinosaurs.”] 

NARRATOR: And of course, if it wasn’t a reptile at all, then it’s really not a dinosaur.

[Footage of a wooly mammoth fossil on display in the Museum halls.]

BENSON: And that includes things like wooly mammoths, which are giant mammals 

[An illustration of a wooly mammoth shows it covered in dense brown fur, with an elephant-like trunk and tusks.]

BENSON: –that are actually a type of extinct elephant. 

[A photo of a Dimetrodon fossil appears.]

BENSON: It also includes an early relative of mammals called Dimetrodon, which appears– 

[An illustration of a Dimetrodon makes it appear very scaly, with a huge bony sail on its back. Its teeth protrude like a crocodile’s.] 

BENSON: –extremely reptilian but is actually more closely related to us than it is to dinosaurs. 

[Museum visitors walk among the dinosaur fossils on display in the halls.] 

NARRATOR: Without dino DNA, the careful study of extinct animals’ anatomy is still the best way to construct the prehistoric family tree. 

[Credits roll.]