Dino card No. 0801 of 2,027

Hesperornis

Say it: HESS-per-OR-nis

Name means: “western bird”1

Ate: FishEarly birdsLate Cretaceous

Hesperornis was a giant swimming bird that lived in the time of dinosaurs. It had teeth in its beak and could not fly, but it was a super diver in the ancient seas.1 2

Lived

90 to 66 million years ago5

Late Cretaceous

Fossils found in

North America (Kansas, Montana, South Dakota, Alaska, Canada), Russia, and Sweden5 1

Food

Fish5 2

Length

1.5 to 1.8 m1

estimate for the largest species

Weight

10.6 kg1

estimate

When did it live?

Triassic

Jurassic

Cretaceous

252 million years ago20114566, the asteroid

How big was it?

How long was it?

How heavy was it?

as heavy as 2.5 house cats

as long as 4 house cats nose to tailas long as 10 bananas end to endas heavy as 88 bananas

How big was Hesperornis compared to YOU?

Just maths in your browser. Nothing is saved or sent anywhere.

cool stuff

Fun facts

Hesperornis was one of the first birds to give up flying and become a full-time swimmer.2

Its legs were placed far back on its body, like a loon, making it clumsy on land but a powerful diver.1

Hesperornis had teeth in its beak, which is rare for birds. It used them to catch fish.1 2

The first fossils of Hesperornis were found by famous fossil hunter Othniel Charles Marsh in 1870 in Kansas.1 2

Several species of Hesperornis lived from about 90 to 66 million years ago, during the Late Cretaceous.5

Hesperornis fossils have been found in many places, including Canada, the United States, Russia, and Sweden.5

AI-made picture of Hesperornis — An AI-made picture of how Hesperornis might have looked, made by a computer from what scientists know. It is a guess: the real animal may have looked different, and nobody knows its true colours.

you asked

Most asked questions about Hesperornis

?How big was Hesperornis?

About 1.5 to 2 metres (4.9 to 6.6 ft) long and weighed around 10.6 kilograms (23 lb).1

?Did Hesperornis have teeth?

Yes, it had teeth in its beak, which is rare for birds. The teeth sat in a groove, not in individual sockets.1

?Could Hesperornis fly?

No, it could not fly. Its wings were tiny and useless for flight, and its breastbone lacked a keel for flight muscles.1 3

?What did Hesperornis eat?

It ate fish, which it caught with its tooth-lined beak while diving in the sea.4

?When did Hesperornis live?

It lived during the Late Cretaceous period, about 83.6 to 72 million years ago, and possibly into the early Maastrichtian.1

?Where was Hesperornis found?

Fossils have been found in Kansas, Canada, Russia, Sweden, and other places, mostly in marine rocks.1

?Could Hesperornis walk on land?

It was clumsy on land. Its legs were placed far back, so it probably pushed itself along on its belly like a seal.1

Ask Rex about Hesperornis

Rex only answers questions about this page. 10 questions a month.

Rex is an AI and can make mistakes. He runs on servers in the EU and questions are never saved. Never type your name or other personal things.

Myth buster

Myth: Some people think Hesperornis was a dinosaur.

Truth: Hesperornis was a bird, not a dinosaur. Birds evolved from dinosaurs, but Hesperornis itself is classified as a bird.1

For dino experts

Scientific name: Hesperornis
Named by: Marsh 18725
Group: Early birds
Family / clade: Hesperornithidae5
Classification: Theropoda > Avialae5
Age of the rocks: 90 to 66 million years (Coniacian / Maastrichtian)5
Rock formations: Pierre Shale, Rybushka, Niobrara5
Countries: Canada, USA, Russia, Sweden5
Fossil records: 65 in the Paleobiology Database5
Also known as: Coniornis, Hargeria, Lestornis (older names now counted as the same animal)5
Discovery: Othniel Charles Marsh discovered the first Hesperornis fossil in 1870 near the Smoky Hill River in Kansas. He named it Hesperornis regalis in 1872.1 2
Still debated: Scientists are still debating exactly how many species of Hesperornis existed, because many fossils are incomplete.1

Where the facts come from

Hesperornis (en.wikipedia.org)
The Hesperornithiformes: A Review of the Diversity, Distribution, and Ecology of the Earliest Diving Birds (mdpi.com)
Hesperornis - Scholars | Britannica Kids | Encyclopedia (kids.britannica.com)
Hesperornis Facts, Artwork, Information - National Geographic | National Geographic (nationalgeographic.com)
Hesperornis in The Paleobiology Database (CC BY 4.0): age, places, rock formations, classification.

Every fact on this page has a number that points to its source. If we got something wrong, sorry, we are dino fans, not a science journal. Tell us at [email protected] and we will fix it.

Rex is hungry! Dino Wiki is a dad's project for his dino-loving son, free with no ads. Grown-ups can feed Rex a snack to help keep it online.Feed Rex