Videos

[MUSIC]

Inside the American Museum of Natural History’s Hall of Vertebrate Origins, where fossils of a large sea turtle and long-necked swimming reptile hang from the ceiling. In the center, a mosasaur fossil behind glass, and the camera cuts into a close-up of its skull with many long sharp teeth.

AMELIA ZIETLOW (Ph.D. Candidate, Richard Gilder Graduate School): Mosasaurs are a group of extinct marine lizards that lived during the late Cretaceous.

The camera pans across a much smaller mosasaur fossil behind glass.

ZIETLOW: Imagine a Komodo dragon except-

A model mosasaur skull sits next to a plastic grey replica of what a mosasaur would have looked like alive. Its mouth is wide open showing many teeth.

ZIETLOW: -it's the size of a school bus with flipper-like limbs, a shark-like tail, and an extra row of teeth on the roof of its mouth.

AMELIA ZIETLOW appears on screen, speaking to the camera. Behind her is the same large mosasaur fossil in the Museum hall.

ZIETLOW: I think the biggest misconception is that they are dinosaurs, which is not the case.

A painting of a mosasaur chasing huge fish amongst the surf of the ocean appears. The painting becomes blurry and the American Museum of Natural History logo appears on top of it.

MENG JIN (Curator, Division of Paleontology): We have many students come here-

MENG JIN appears on screen, speaking to camera. Text appears: “Meng Jin, Curator, Division of Paleontology”.

MENG: -particularly working on dinosaurs. She’s the only student interested in mosasaurs.

Workers remove panes of glass from in front of the large mosasaur fossil on display.

ZIETLOW: It was really exciting when the glass came off,

Hands measure the jaw and teeth of the mosasaur skull with calipers. ZIETLOW holds a small scanner that flashes white light at the smaller mosasaur fossil.

ZIETLOW: because the glass has not come off in 30 years since the hall has been renovated.

ZIETLOW appears on screen, speaking to the camera. Text appears: “Amelia Zietlow, Ph.D. Candidate, Richard Gilder Graduate School.”

ZIETLOW: So it was really cool to be the first person to touch these fossils in 30 years. Part of my research here is describing that fossil so we can-

Hands use calipers to measure the vertebrae of the smaller mosasaur specimen.

ZIETLOW: -better understand that group of mosasaurs as a whole.

ZIETLOW looks at the large skull of the fossil mosasaur, without glass in front of it. Camera pans across the teeth of the skull. Close-up of one of the fins of a fossil mosasaur, which looks almost like a hand with outstretched fingers.

ZIETLOW: Mosasaurs were fully marine, which means that they did not return to the land.

ZIETLOW reappears on screen speaking to the camera.

ZIETLOW: Their fossils have been found on every continent, including Antarctica, because they were living in the oceans and crossing the oceans. We actually have fossils of the same species in Europe as we do on the east coast of North America. 

ZIETLOW pulls a long flat drawer out of a cabinet, which contains a mosasaur fossil embedded in rock. Camera pans over the long teeth of the fossil, with text appearing: “100-66 million years ago”.

ZIETLOW: Mosasaurs lived between 100 and 66 million years ago,

A mosasaur skull, broken in several places, sits on a cart with teeth pointing up.

ZIETLOW: and they went extinct with the same asteroid that killed the dinosaurs.

A painting showing what a mosasaur might have looked like, swimming in a school of prehistoric fish.

MENG: Mosasaurus, it's a marine reptile. Specifically, it's a marine lizard.

MENG reappears on screen. 

MENG: So this animal, although it has big teeth, it's not a dinosaur.

A charcoal sketch of a long-necked dinosaur appears, then as water fills the screen with a [SPLASH] a charcoal sketch of a mosasaur appears beneath the surface.

MENG: We don't see any dinosaur living in the marine environments.

A graphic of a bracket labeled with the text “reptiles” draws onto the screen. Beneath the bracket are silhouettes of snakes, a mosasaur, a T. rex, a chicken, a sea turtle, a crocodile, and two lizards.

ZIETLOW: The reptile evolutionary tree has two main branches, the archosaurs and the lepidosaurs.

Two more graphic brackets draw themselves below the reptile bracket, with text labelling them: “lepidosaurs” on the left and “archosaurs” on the right. 

ZIETLOW: Dinosaurs, birds, crocs, and turtles belong to the archosaur branch, 

The silhouettes of the crocodile, chicken, sea turtle, and T. rex float over to rest under the “archosaur” bracket. 

ZIETLOW: and mosasaurs and other lizards and snakes belong to the lepidosaur branch.

The silhouettes of the mosasaur, snakes, and lizards float over to rest under the “lepidosaur” bracket. MENG reappears on screen speaking to camera.

MENG: Mosasaurs have been studied for many years but still there are very many basic issues. Like right now for example,

ZIETLOW holds up a skull of a fossil mosasaur.

MENG: whether it more closely related to lizards-

A circle inset shows a Komodo dragon skeleton.

MENG: -or snakes,

A circle inset shows a python skeleton.

MENG: it’s still a debatable issue.

Camera pans across a diorama showing a Komodo dragon biting into a boar. Text appears: “Komodo dragon: 10 ft (3 m)”

ZIETLOW: The biggest lizards alive today are the Komodo dragons, which are about ten feet long.

The camera pans across a diorama of a reticulated python slithering out of a tree. Text appears: “reticulated python: 26 ft (8 m)”

ZIETLOW: The largest pythons get to be at 26 to 30 feet long.

In the Museum collections, Zietlow kneels next to a huge lower jaw of a mosasaur and uses a tape measure to find its length. Text appears: “mosasaur: 50 ft (15 m)”

ZIETLOW: The biggest mosasaurs that we have found so far are estimated to have been almost 50 feet long, which is bigger than a school bus and bigger than any T.rex. 

ZIETLOW reappears on screen speaking to camera.

ZIETLOW: So they're very big. [LAUGHS]

ZIETLOW pulls out another drawer of fossil bones in the Museum collections space.

MENG: We want to study their evolutionary path, 

A large black fossil bone sits next to two small white bones. The fossil is labeled “mosasaur” and the small bones are labeled “iguana” and “monitor lizard”.

MENG: how they became a terrestrial animal

Camera pans across a plastic model of what a mosasaur would have looked like alive, ending on the head with the mouth open wide.

MENG: that gradually evolved into an aquatic animal.

Hands place a replica Komodo dragon skull down next to a real fossil mosasaur skull, which is at least 3 times larger. Text labels them respectively as “Komodo dragon” and “mosasaur”. 

MENG: Animals going from the terrestrial life, going back into ocean tend to become larger body-sized-

MENG reappears on screen.

MENG: -because you don't have to carry your body. If you walk on the ground,

A tortoise moves slowly and steadily across the ground. 

MENG: the gravity will bring you down to the surface. You have to spend more energy. 

A humpback whale swims slowly through the water.

MENG: But in the water you don't have that problem.

A painting of a large multi-colored mosasaur trying to eat a large lobster appears.

ZIETLOW: We think mosasaurs were able to grow to be so big because they had a lot of food available to them.

ZIETLOW reappears on screen speaking to camera.

ZIETLOW: Mosasaurs would eat basically anything and everything that moved. We know that based on the shapes of their teeth, their actual stomach contents, and bite marks on other animals that lived with mosasaurs. 

Camera focuses on a single large mosasaur tooth. ZIETLOW holds aloft a big fossil mosasaur tooth and indicates its shape.

MENG: Similar to mammals,

Camera pans across an upper jaw of a mosasaur, showing teeth and tooth sockets.

MENG: in mosasaurs, the teeth are

Camera pans across a jawbone showing deep sockets. Text appears: “mosasaur: sockets for teeth”

MENG: implanted into the jawbone.

Camera pans across another jawbone, which shows teeth growing up alongside the jaw (not inside the jaw bone). Text appears: “Komodo dragon: teeth grow alongside the jaw” 

MENG: This is different from the other reptiles.

MENG reappears on screen speaking to camera.

MENG: It’s more stable, so you can apply more power on those teeth to handle your prey, to handle your food. 

Camera pans across a toy mosasaur with bumpy, ridged skin, looking similar to a crocodile.

ZIETLOW: People might think that mosasaurs looked like crocodiles, with armored skin,

Camera zooms in on a smooth fossil sitting behind a magnifying glass.

ZIETLOW: when really that’s not the case. We actually have skin impressions of real mosasaur skin, 

Camera zooms in on a section of fossil mosasaur skin that looks a bit like snake skin – diamond shaped, but with a ridge in the section of each small diamond.

ZIETLOW: where we can see that the scales are kind of diamond shaped and they have a little keel down the middle,

ZIETLOW reappears on screen speaking to camera. 

ZIETLOW: which is very similar to if you've ever seen shark skin under a microscope.

An image of diamond-shaped denticles that make up shark skin, which also have a ridge in the middle.

ZIETLOW: So that would have helped them to swim faster.

Camera pans across the large mosasaur fossil on display in the Museum’s halls, from the beginning of the video.

ZIETLOW: This is Tylosaurus proriger.

A black-and-white photo of a man standing in a work apron from a century ago next to the same mosasaur fossil on display.

ZIETLOW: This fossil was found in the 1800s.

ZIETLOW crouches on the ground using a handheld scanning device to take lots of detailed photos of the surface of the mosasaur fossil.

ZIETLOW: And it has not been described in the literature since.

Close-up of the skull of the smaller mosasaur fossil on display in the Museum’s halls. 

ZIETLOW: The little one, the Clidastes has actually 

ZIETLOW uses a handheld scanner to scan the smaller mosasaur fossil.

ZIETLOW: never been formally described in the scientific literature,

ZIETLOW reappears on screen speaking to camera.

ZIETLOW: which is a little bit insane if you think about it,

ZIETLOW’s hands measure the flipper of the smaller mosasaur specimen with calipers.

ZIETLOW: because it is a nearly complete skeleton

A drawer containing a fossil mosasaur skull and the lower jaw is pulled out from a cabinet.

ZIETLOW: and the skull is in almost perfect condition.

MENG reappears on screen speaking to camera. 

MENG: Perfectly preserved fossils are very very rare.

Camera pans along the full length of the smaller mosasaur specimen, which looks nearly complete.

MENG: The percentage of real specimens

Camera pans across the larger mosasaur fossil in the Museum’s halls.

MENG: on display are the highest

Camera focuses on parts of the skeleton, which are hand labeled on the bone as “cartilaginous sternal ribs” and “tibia”

MENG: in any museum.

ZIETLOW and another scientist look at a computer screen with the mosasaur fossil in the background.

ZIETLOW: I hope that by looking at different features in

The camera shows the computer screen, which is rotating around a 3D scan of the same fossil behind the scientists.

ZIETLOW: a little bit more detail, and using modern techniques

ZIETLOW looks at a computer screen where there is a CT scan of a skeleton on screen.

ZIETLOW: like CT scanning and surface scanning,

The large mosasaur fossil on display in the Museum halls is slowly surrounded with visitors looking at it and passing by.

ZIETLOW: we can better understand mosasaurs.

Credits roll.

Video
AMNH / L. Stevens 

Images / Archive
AMNH Library
Amelia Zietlow
Biodiversity Heritage Library
Dmitry Bogdanov
Henry Sharpe
Pascal Deynat
Pond5

Replicas & Models
Bone Clones
Mattel
PNSO
Ruadhrí Brennan, Scaled Beast

Music
”Wonders & Illusions” by Matthew William Rees (PRS) / Warner/Chappell Production Music
"Neutralism" by Kriso Lindberg (GEMA) / Warner/Chappell Production Music
”Data Discovery” by Richard Stephan Dutnall (PRS) / Warner/Chappell Production Music 

Sound Effects
FreeSound.org / itinerantmonk108

© American Museum of Natural History