Falcarius
fal-KAIR-ee-us
"sickle cutter"
- Lived
- 143 to 133 million years ago, Early Cretaceous
- Diet
- Omnivore
- Group
- Theropods
- Found in
- United States
- Named by
- Kirkland et al. 2005
Where its fossils were found
The evidence
Today
140 million years ago
Habitat
It lived on a floodplain where springs and river floods buried the bones now found in the Cedar Mountain Formation. Utahraptor and Gastonia also come from this formation.
Field notes
About Falcarius
What it was like
Falcarius was one of the earliest known therizinosaurs, the strange, long-clawed dinosaurs that came from meat-eating ancestors but mostly ate plants. It had a small head, a long neck and tail, and curved claws on its hands.
Its teeth were small and leaf-shaped, suited to plants, so it may have eaten plants and small animals. It shows how this group made the change from hunting to plant eating.
Its world
It lived in the Early Cretaceous in what is now Utah, in the United States. Its bones come from the Cedar Mountain Formation, where it shared the land with the giant raptor Utahraptor and the armored Gastonia.
How it was found
Kirkland and colleagues named Falcarius in 2005. A bone bed in Utah holds the remains of many individuals, from young to fully grown.
Field gallery
More views of Falcarius
Scenes reconstructed from the available fossil evidence.
1 of 3
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 Falcarius.
The evidence
The science behind Falcarius
Which parts of the picture come from its own bones, and which come from its relatives.
From its own fossils
- Many separate bones from a bonebed preserve much of the body, including long arms and curved hand claws.
- Its lower legs and feet were relatively long, with the main weight carried on three toes.
- Skull fragments suggest a low, broad snout and large, rounded eye sockets.
Borrowed from relatives
- Much of the body is restored from its own bones; Beipiaosaurus helps fill gaps at the front of the skull.
- Simple feathers are inferred from the preserved filaments of Beipiaosaurus.
Still unknown
- The complete shape of its snout and the teeth at the front of the upper jaw.
- Exactly how much of its food was plants or small animals.
- Its feather covering and color.
Often drawn wrong
- Its curved hand claws were much shorter than the giant claws of Therizinosaurus.
- Its feet had three main supporting toes; giving it four equal supporting toes copies later therizinosaurs.
Discovery timeline
- 2005Named itKirkland et al.
- 2009Close relativeXu, Zheng & You
- 2010Full descriptionZANNO
- 2025SkullFreimuth & Zanno
Key papers
The research behind what we know of Falcarius
Named it
Named an early therizinosaur whose teeth and body help trace the transition from meat-eating ancestors toward plant eating.
A primitive therizinosauroid dinosaur from the Early Cretaceous of Utah. Nature 435: 84-87
Read the paper : A primitive therizinosauroid dinosaur from the Early Cretaceous of Utah (opens in a new tab)Close relative
Found broad feather filaments in Beipiaosaurus, a relative used to infer a possible feather covering for Falcarius.
A new feather type in a nonavian theropod and the early evolution of feathers. Proceedings of the National Academy of Sciences 106: 832-834
Read the paper : A new feather type in a nonavian theropod and the early evolution of feathers (opens in a new tab)Full description
Described the skeleton in detail, including its long lower legs, grasping hands and differences from later therizinosaurs.
Osteology ofFalcarius utahensis(Dinosauria: Theropoda): characterizing the anatomy of basal therizinosaurs. Zoological Journal of the Linnean Society 158: 196-230
Read the paper : Osteology ofFalcarius utahensis(Dinosauria: Theropoda): characterizing the anatomy of basal therizinosaurs (opens in a new tab)Skull
Added skull and tooth material, suggested a low, broad snout, and corrected an earlier identification of a supposed nose bone.
New craniodental materials of Falcarius utahensis (Theropoda: Therizinosauria) reveal patterns of intraspecific variation and cranial evolution in early coelurosaurians. The Anatomical Record 309: 1995-2048
Read the paper : New craniodental materials of Falcarius utahensis (Theropoda: Therizinosauria) reveal patterns of intraspecific variation and cranial evolution in early coelurosaurians (opens in a new tab)
Close relatives
Other members of Therizinosauria
Sources: Wikidata