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Torosaurus, Late CretaceousHell Creek Formation, South Dakota · named 1891
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Torosaurus

TOR-oh-SORE-us

"perforated lizard"

Type species Torosaurus latus

Lived
84 to 66 million years ago, Late Cretaceous
Diet
Herbivore
Length
about 7.5 m (25 ft)
Group
Ceratopsians, Ceratopsidae
Found in
United States
Named by
Marsh 1891

Size comparison

To scale

Where its fossils were found

The evidence

Today

6 finds

75 million years ago

Map: C. R. Scotese, PALEOMAP

Habitat

Wooded river plains with shallow channels and open patches of low vegetation. Tyrannosaurus, Triceratops and Ankylosaurus lived in the same region.

Field notes

About Torosaurus

What it was like

Torosaurus was a large, plant-eating ceratopsian with a huge, bony frill extending back from its skull, pierced by two large openings, and a short horn above its nose. It grew to about 7.5 meters (25 feet) long and likely used its beaked mouth to crop tough, fibrous plants.

Its frill was thin and lightweight, supported mostly along its outer edge, and carried at least five pairs of small hornlets along the back margin. Scientists still debate whether Torosaurus was truly a separate genus or simply a fully grown Triceratops, since the two look similar apart from the frill.

Its world

Torosaurus lived from about 84 to 66 million years ago, in the Late Cretaceous, across what is now the western United States, including South Dakota, Wyoming, New Mexico, and North Dakota.

It lived alongside Tyrannosaurus, Triceratops, the armored Ankylosaurus, and the dome-headed Pachycephalosaurus, in an ecosystem thick with large, plant-eating ceratopsians.

How it was found

Marsh named Torosaurus in 1891. Around six fossil finds are known, and the question of whether Torosaurus represents a mature Triceratops rather than its own genus remains unresolved among paleontologists. Its close relatives include Triceratops, Styracosaurus, and Pentaceratops, all members of the horned dinosaur family Ceratopsidae.

Field gallery

More views of Torosaurus

Scenes reconstructed from the available fossil evidence.

Torosaurus in its habitat, photo 1

1 of 7

Lived alongside

Found in the same rock formations

A rock formation can hold fossils laid down millions of years apart, so not every animal here met Torosaurus.

The evidence

The science behind Torosaurus

Which parts of the picture come from its own bones, and which come from its relatives.

From its own fossils

  • Skulls show a long frill with large openings in the bone, long brow horns and a smaller nose horn.
  • The broad beak and tightly packed cheek teeth formed a plant-cropping and slicing mouth.
  • A thigh bone associated with a frill shows that at least one Torosaurus was still growing.

Borrowed from relatives

  • Triceratops and other horned dinosaurs help fill gaps in the body and limbs.
  • Skin probably covered the openings in the bony frill, as in other horned dinosaurs.

Still unknown

  • Whether Torosaurus was a separate genus or a growth stage of Triceratops.
  • Its color and the exact shape of the skin over the frill.
  • How the horns and frill changed from hatchling to adult.

Often drawn wrong

  • The openings in the frill bone should be covered with skin, rather than shown as holes through the living animal.
  • The frill edge carried small hornlets rather than a crown of long spikes.

Discovery timeline

  1. 1891Named itMarsh
  2. 2012Growing upLongrich & Field
  3. 2013SkullMaiorino et al.
  4. 2016New findMcDonald, Campbell & Thomas
  5. 2022Growing upMallon et al.

Key papers

The research behind what we know of Torosaurus

Close relatives

Other members of Ceratopsidae

Sources: Wikidata