Segnosaurus Facts
Pronunciation: SEG-no-SORE-us
Name meaning: Slow Lizard
| Diet | Herbivore |
| Height | 3m |
| Length | 6m |
| Weight | 1.5 tonnes |
| Environment | Land |
| Era | Cretaceous |
| Period | Late Cretaceous |
| Type | Theropod |
| Location | Mongolia |
Segnosaurus was a remarkable theropod dinosaur that lived in what is now southeastern Mongolia during the Late Cretaceous period, approximately 102 to 86 million years ago. Despite being a theropod—the same group that includes fearsome predators like Tyrannosaurus rex—Segnosaurus was entirely herbivorous, representing one of the most unusual evolutionary developments in dinosaur history.
This fascinating dinosaur measured around 6 metres in length and stood about 3 metres tall at the hip, weighing roughly 1.5 tonnes. Multiple well-preserved but incomplete specimens were discovered in the Gobi Desert during the 1970s, providing scientists with valuable insights into its anatomy. The known fossils include parts of the lower jaw, neck and tail vertebrae, pelvis, shoulder girdle, and limb bones, though sadly some specimens have been damaged or gone missing since their original collection.
As a plant-eater, Segnosaurus would have used its powerful claws and long neck to reach vegetation, much like a giant ground sloth. Its robust build and specialised anatomy suggest it was well-adapted to processing tough plant material. The discovery of Segnosaurus helped scientists understand the incredible diversity of theropod dinosaurs and how some evolved from meat-eaters into peaceful herbivores.
Interestingly, remains originally thought to belong to Allosaurus found in Japan were recently reassigned to Segnosaurus in 2025, expanding our knowledge of where these unusual theropods lived during the Cretaceous period.
What made Segnosaurus distinctive?
Segnosaurus had large, powerful claws on its hands, a long neck for reaching vegetation, and a robust, heavily-built body unusual for most theropods. Its hip structure was distinctively modified compared to typical meat-eating theropods, reflecting its plant-eating lifestyle.
Behaviour
Segnosaurus likely spent much of its time foraging for plants, using its long neck to reach higher vegetation and its powerful claws to strip leaves and branches. As a herbivore, it would have been a peaceful creature, possibly living in small groups while browsing the Late Cretaceous forests of Mongolia.
Segnosaurus FAQ
What did Segnosaurus eat?
Segnosaurus was herbivorous, feeding entirely on plants. It used its long neck to reach vegetation and its powerful claws to strip leaves and branches from trees and shrubs in the
Late Cretaceous forests of Mongolia.
How big was Segnosaurus?
Segnosaurus measured approximately 6 metres in length and stood about 3 metres tall at the hip. It weighed roughly 1.5 tonnes, making it a substantial but not gigantic dinosaur compared to other large theropods.
When did Segnosaurus live?
Segnosaurus lived during the
Late Cretaceous period, approximately 102 to 86 million years ago. This was during the latter part of the Age of Dinosaurs, well before the mass extinction event that ended the Cretaceous.
Where was Segnosaurus found?
Segnosaurus fossils were discovered in the Gobi Desert of southeastern Mongolia during the 1970s. Recently, fossils originally thought to be
Allosaurus found in Japan have also been reassigned to Segnosaurus, expanding its known range.
How do you pronounce Segnosaurus?
Segnosaurus is pronounced 'SEG-no-SORE-us', with the emphasis on the first and third syllables. The name breaks down as 'Segno' meaning slow and 'saurus' meaning lizard.
What does Segnosaurus mean?
Segnosaurus means 'slow lizard' in Latin. The name was chosen to reflect the scientists' impression that this was likely a slow-moving dinosaur, though we don't know for certain how fast it could actually move.
How fast could Segnosaurus run?
The speed of Segnosaurus is unknown, as no detailed studies have been conducted on its locomotion. Given its name means 'slow lizard' and its robust build, it was probably not a fast runner, but this remains speculative.
What type of dinosaur was Segnosaurus?
Segnosaurus was a theropod dinosaur, belonging to the family Therizinosauridae. This makes it particularly unusual, as most theropods were carnivorous, but Segnosaurus and its relatives evolved to become herbivorous.
Was Segnosaurus related to birds?
Yes, as a theropod dinosaur, Segnosaurus was more closely related to modern birds than to other dinosaur groups. All theropods, including plant-eating ones like Segnosaurus, share a common ancestor with birds.
How many Segnosaurus fossils have been found?
Multiple incomplete but well-preserved Segnosaurus specimens were discovered in the 1970s, though the exact number isn't specified in scientific literature. Unfortunately, some of these original specimens have since been damaged or gone missing.
