Moros intrepidus
Moros intrepidus was a small, lightly built predatory dinosaur that looked much like a scaled-down cousin of Tyrannosaurus rex. It weighed roughly 70–80 kilograms, stood a little over a metre tall at the hip and was perhaps three metres long including its long counterbalancing tail.
Moros intrepidus
Moros intrepidus
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Quick facts
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Weight
60–80 kg
Length
2.5–3.5 m
Diet
Carnivore
Period
Cretaceous
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60–80 kg
2.5–3.5 m
Cretaceous
Bipedal
1–1.3 m
40 km/h
Carnivore
Regions where fossils have been found, shown by present-day continent.
The timeline shows the whole age of dinosaurs – and how much time has passed since. The glowing part is when Moros intrepidus lived.
million years ago
Lived 97–96 million years ago
If the whole age of dinosaurs were a single day, Moros intrepidus lived at 20:04.
Chapter • Meet the dinosaur
Moros intrepidus was a small, lightly built predatory dinosaur that looked much like a scaled-down cousin of Tyrannosaurus rex. It weighed roughly 70–80 kilograms, stood a little over a metre tall at the hip and was perhaps three metres long including its long counterbalancing tail. Its legs were strikingly long and slender for its body size, and the foot was arctometatarsalian, with the central metatarsal pinched at the top — a design linked in later tyrannosaurs to springy, energy-efficient running. Because several small tyrannosauroids from China are preserved with simple filamentous feathers, most reconstructions give Moros a downy coat, even though no skin impressions are known for this species. Moros was not the top predator of its world. It shared the landscape with far larger meat-eaters, including big carcharodontosaurs, and probably made its living as a quick, alert hunter of lizards, early mammals, juvenile dinosaurs and other small prey. Its teeth are classic tyrannosauroid: blade-like, laterally compressed and strongly serrated, built for slicing flesh and tendon rather than for the bone-crushing bite of its gigantic later relatives. The only known specimen consists of a partial hind limb — femur, tibia and metatarsals — together with a few isolated teeth. Thin sections through the bone reveal growth rings, and counting them shows the animal was at least six or seven years old and close to full size when it died. That confirms Moros was genuinely a small dinosaur, not simply a juvenile of something larger. The fossil was found in 2013 in the Mussentuchit Member of the Cedar Mountain Formation in Emery County, Utah, and was described in 2019 by Lindsay Zanno and colleagues. The genus name refers to Moros, the Greek personification of impending doom, while intrepidus means "intrepid", a nod to the boldness of tyrannosaur dispersal between continents. The discovery matters because it helps close a roughly 70-million-year gap in the North American tyrannosaur record, showing that the group was still modest in size shortly before its dramatic rise to giant proportions.
Chapter • Where it lived
Moros intrepidus lived about 96.4 million years ago, in the early Cenomanian stage of the Late Cretaceous. Every known fossil comes from the Mussentuchit Member of the Cedar Mountain Formation in Emery County, central Utah, USA. The setting was a warm, humid coastal lowland of braided rivers, floodplains, swampy backwaters and forests of conifers, ferns and early flowering plants, lying along the western shore of the great inland sea that then split North America in two. The same beds have yielded turtles, crocodyliforms, early mammals, iguanodontians, ankylosaurs and larger predatory theropods.
Chapter • Wild behavior
There is no direct evidence for the social life of Moros intrepidus: the species is known from a single individual, with no trackways or bonebeds attributed to it. Some other tyrannosauroids are known from groups of individuals preserved together, which has been interpreted as possible pack behaviour, but that reading remains debated. A small, fast predator like Moros most plausibly hunted alone or in loose, temporary groups, though this stays a hypothesis.
The genus name comes from Moros, the Greek personification of impending doom — a hint at the giant tyrannosaurs to come.
At around 78 kilograms, Moros weighed about as much as an adult human, while Tyrannosaurus rex could be more than a hundred times heavier.
Growth rings in the leg bones show the individual was at least six or seven years old and nearly fully grown.
The find helps fill a gap of roughly 70 million years in the North American tyrannosaur fossil record.
Long, slim legs and an arctometatarsalian foot suggest Moros was a fast and enduring runner.
Phylogenetic analyses place Moros close to Asian tyrannosauroids, hinting that the group entered North America from Asia.
In only about 16 million years, North American tyrannosaurs went from Moros-sized to multi-tonne giants.
The entire species is known from one partial hind limb and a handful of teeth — proof of how much small fossils can reveal.
Chapter • Scientific place
Communications Biology (Springer Nature)
Reviewed: 9/6/2026
Authoritative overview of the species: anatomy of the hindlimb holotype, body size (~78 kg), skeletal maturity at 6–7 years, age and evolutionary significance.
Open sourceCommunications Biology (Springer Nature)
Reviewed: 9/6/2026
Original description by Zanno et al. (2019) erecting Moros intrepidus and placing it phylogenetically within Theropoda: Coelurosauria: Tyrannosauroidea.
Open sourceCommunications Biology (Springer Nature)
Reviewed: 9/6/2026
Documents the holotype locality and the sole known occurrence of the species in the Mussentuchit Member of the Cedar Mountain Formation, Emery County, Utah, USA.
Open sourcePeerJ
Reviewed: 9/6/2026
Peer-reviewed analysis of the fauna and depositional palaeoenvironment of the Mussentuchit Member, the coastal-plain ecosystem in which Moros intrepidus lived.
Open sourceCommunications Biology (Springer Nature)
Reviewed: 9/6/2026
Describes Moros intrepidus as a small-bodied, cursorial predatory tyrannosauroid, including a referred theropod tooth, establishing its carnivorous diet.
Open sourceCretaceous Research (Elsevier)
Reviewed: 9/6/2026
Extinct taxon; conservation status NE
Open sourceCommunications Biology (Springer Nature)
Reviewed: 9/6/2026
Authoritative overview of the species: anatomy of the hindlimb holotype, body size (~78 kg), skeletal maturity at 6–7 years, age and evolutionary significance.
Open sourceCommunications Biology (Springer Nature)
Reviewed: 9/6/2026
Authoritative overview of the species: anatomy of the hindlimb holotype, body size (~78 kg), skeletal maturity at 6–7 years, age and evolutionary significance.
Open sourceCommunications Biology (Springer Nature)
Reviewed: 9/6/2026
Authoritative overview of the species: anatomy of the hindlimb holotype, body size (~78 kg), skeletal maturity at 6–7 years, age and evolutionary significance.
Open source