Earliest Jurassic U-Pb ages from carbonate deposits in the Navajo Sandstone, southeastern Utah, USA
Geology (Geological Society of America)
Reviewed: 9/10/2026
Extinct taxon; conservation status NE
Open source
Sarahsaurus aurifontanalis
Sarahsaurus was a small, bipedal plant-eating dinosaur with a long neck, a compact barrel-shaped body and a relatively small skull filled with leaf-shaped, coarsely serrated teeth. At roughly 3.5–4.3 metres long and 70–113 kilograms, it was no bigger than a large pony, yet it was solidly built.
Sarahsaurus
Sarahsaurus aurifontanalis
AI reconstruction · Size is not always to scale · © Dinofacts
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Weight
70–113 kg
Length
3.5–4.3 m
Diet
Herbivore
Period
Jurassic
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70–113 kg
3.5–4.3 m
Jurassic
Bipedal
1–1.5 m
Herbivore
2 recorded fossil finds in United States. First described in 2011 by Rowe et al..
Sites and counts from the Paleobiology Database
The timeline shows the whole age of dinosaurs – and how much time has passed since. The glowing part is when Sarahsaurus lived.
million years ago
Lived 190–183 million years ago
If the whole age of dinosaurs were a single day, Sarahsaurus lived at 08:27.
Chapter • Meet the dinosaur
Sarahsaurus was a small, bipedal plant-eating dinosaur with a long neck, a compact barrel-shaped body and a relatively small skull filled with leaf-shaped, coarsely serrated teeth. At roughly 3.5–4.3 metres long and 70–113 kilograms, it was no bigger than a large pony, yet it was solidly built. Its most striking feature was the hand: the forelimbs were short but exceptionally powerful, and the thumb carried a large curved claw. The scientists who described it noted that the hand was about the size of a human hand but far stronger. Sarahsaurus walked on its hind legs with the back held horizontally and the tail carried clear of the ground.
Chapter • Where it lived
Sarahsaurus lived about 196–183 million years ago in the Early Jurassic (Sinemurian–Pliensbachian), in what is now Coconino County, northern Arizona. All confirmed material comes from the Kayenta Formation, chiefly the Gold Spring locality. The setting was semi-arid and strongly seasonal: intermittent rivers and waterholes fringed with greenery, dry plains and floodplains, and to the north the vast dune fields that later became the Navajo Sandstone. Ferns, cycads, conifers and horsetails provided browse during the wetter intervals.
Chapter • Wild behavior
Several individuals have been recovered from the same fossil-bearing beds at Gold Spring, which may indicate that these animals moved in loose groups or at least gathered at the same water sources. Post-mortem transport by floodwaters cannot be ruled out, however, so there is no firm evidence of true herding. Nothing is known about parental care or territorial behaviour.
The genus honours Sarah Butler of Austin, Texas, a supporter of the Texas Memorial Museum — an unusual case of a dinosaur named after a patron rather than a scientist.
The species name aurifontanalis means 'golden spring', after the Gold Spring locality in northern Arizona.
One skeleton sat misidentified in the Harvard collections for decades, catalogued as the South African relative Massospondylus, before being reassigned to Sarahsaurus.
Its hands were far more robust than expected in a strict herbivore, prompting debate over whether it also tore up roots or occasionally took animal food.
It is one of only three securely known Early Jurassic sauropodomorphs from North America, alongside Anchisaurus and Seitaad.
The fossils support the idea that long-necked plant-eaters colonised North America in several separate waves after the end-Triassic mass extinction.
It shared its landscape with the predator Dilophosaurus and the small armoured ornithischian Scutellosaurus.
The specimens come from Navajo Nation land in Arizona and were collected under permit.
Chapter • Scientific place
Geology (Geological Society of America)
Reviewed: 9/10/2026
Extinct taxon; conservation status NE
Open sourcePLOS ONE
Reviewed: 9/10/2026
Comprehensive peer-reviewed monographic treatment of the skeletal anatomy, body size, growth and systematics of Sarahsaurus, serving as the general overview source.
Open sourcePLOS ONE
Reviewed: 9/10/2026
Comprehensive peer-reviewed monographic treatment of the skeletal anatomy, body size, growth and systematics of Sarahsaurus, serving as the general overview source.
Open sourcePLOS ONE
Reviewed: 9/10/2026
Comprehensive peer-reviewed monographic treatment of the skeletal anatomy, body size, growth and systematics of Sarahsaurus, serving as the general overview source.
Open sourcejournals.plos.org
Reviewed: 9/10/2026
VERIFY:geological_stage: stored=sinemurian suggested=pliensbachian confidence=high — Marsh & Rowe (2018) place the holotype quarry in the stratigraphic middle third of the Kayenta Formation and report that U-Pb dates on detrital zircons from the quarry matrix corroborate a late Pliensbachian age. The older blanket Sinemurian assignment for the formation is superseded for this taxon's horizon.
Open sourcejournals.plos.org
Reviewed: 9/10/2026
VERIFY:period_start_mya: stored=196 suggested=190 confidence=medium — A start of 196 Ma falls in the Sinemurian, but the detrital-zircon dating reported by Marsh & Rowe (2018) supports a late Pliensbachian age (roughly 188 Ma) for the Sarahsaurus horizon, so the upper bound of the range should not extend into the Sinemurian; the stored end date of 183 Ma remains consistent with published Kayenta zircon ages.
Open sourceProceedings of the Royal Society B: Biological Sciences
Reviewed: 9/10/2026
Peer-reviewed paper by Rowe, Sues & Reisz (2011) that erected Sarahsaurus aurifontanalis and established its phylogenetic placement among basal sauropodomorphs (Massopoda/Plateosauria).
Open sourcePLOS ONE
Reviewed: 9/10/2026
Marsh & Rowe (2018) document all confirmed specimens and their provenance in the Kayenta Formation of Coconino County, northern Arizona, chiefly the Gold Spring locality.
Open sourceJournal of Sedimentary Research (SEPM)
Reviewed: 9/10/2026
Peer-reviewed sedimentological study of the Kayenta Formation and its transition into the Navajo dune field, documenting the semi-arid, seasonally fluvial erg-margin palaeoenvironment Sarahsaurus inhabited.
Open sourceProceedings of the Royal Society B: Biological Sciences
Reviewed: 9/10/2026
The original description reports the coarsely denticulate, leaf-shaped dentition and sauropodomorph craniodental anatomy indicating a herbivorous (plant-browsing) diet.
Open sourcePLOS ONE
Reviewed: 9/10/2026
Comprehensive peer-reviewed monographic treatment of the skeletal anatomy, body size, growth and systematics of Sarahsaurus, serving as the general overview source.
Open source