Dino card No. 1819 of 2,015

Trinacromerum

Say it: try-NAK-roh-MAIR-um

Name means: “three tipped femur”1

Ate: MeatPlesiosaursEarly Cretaceous to Late CretaceousNot technically a dinosaur

Trinacromerum was a fast-swimming marine reptile that lived in the Late Cretaceous seas. It used its long flippers like paddles to chase small fish. Even though it looked a bit like a dolphin, it was actually a plesiosaur, not a dinosaur.1 3

Fun fact: this sea reptile swam while dinosaurs walked on land. Everyone calls them dinos, but they were a different branch of reptiles.

Lived

106 to 66 million years ago3

Early Cretaceous to Late Cretaceous

Fossils found in

Kansas, Texas, Utah, and Wyoming in the USA, and Manitoba and Saskatchewan in Canada3 1

Food

Meat1 3

Length

3 m1

Artist's life restoration of Trinacromerum — How Trinacromerum may have looked, by Nobu Tamura (http://spinops.blogspot.com). CC BY 2.5, via Wikimedia Commons. Scientists still argue about colours and details.

When did it live?

Triassic

Jurassic

Cretaceous

252 million years ago20114566, the asteroid

How big was it?

cool stuff

Fun facts

Trinacromerum's long flippers helped it swim very fast, and scientists think it moved like a 'four-flippered penguin'.1

Its name means 'three tipped femur', which refers to a bone in its hip that had three points.1

Trinacromerum had 46 vertebrae in its spine, including 20 in the neck, 3 in the chest, and 23 in the back.2

Fossils of Trinacromerum have been found in rocks that were once the bottom of a shallow sea that covered central North America.3

It lived from about 106 to 66 million years ago, during the Late Cretaceous period.3

Some scientists once thought Trinacromerum was the same as another plesiosaur called Dolichorhynchops, but now they are considered different.2

Myth buster

Myth: Some people think Trinacromerum was a dinosaur because it lived in the sea and had flippers.

Truth: Trinacromerum was a plesiosaur, a marine reptile, not a dinosaur. Dinosaurs lived on land and had different body shapes.1

For dino experts

Scientific name: Trinacromerum
Named by: Cragin 18883
Group: Plesiosaurs
Family / clade: Polycotylidae3
Classification: Plesiosauria > Sauropterygia3
Age of the rocks: 106 to 66 million years (Albian to Maastrichtian)3
Rock formations: Carlile Shale, Greenhorn Limestone, Pierre Shale3
Countries: USA, Canada3
Fossil records: 18 in the Paleobiology Database3
Discovery: Trinacromerum was first named by Francis W. Cragin in 1888 from fossils found in Kansas, USA. Later, more fossils were found in Canada and other parts of the USA.1 3
Still debated: Scientists still debate whether some fossils belong to Trinacromerum or to its close relative Dolichorhynchops, because their skeletons are very similar.2

Where the facts come from

Trinacromerum (en.wikipedia.org)
PBDB Taxon (paleobiodb.org)
Trinacromerum 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 hello@dinowiki.app and we will fix it.