Open Paleo

Chilesaurus

Novas et al., 2015 CHIH-lee-SOR-us

Named after Chile, the country in South America where it was discovered, combined with Greek sauros meaning 'lizard'. Full meaning: 'Chile lizard'.

149.2–143.1 million years ago Tithonian, Late Jurassic
Late Jurassic stages

Chilesaurus is an extinct genus of herbivorous dinosaur. While its exact classification is uncertain, many researchers believe it is a theropod, with a minority of academics suggesting that it may be an ornithischian. The type and only known species so far is Chilesaurus diegosuarezi. Chilesaurus lived between 148-147 million years ago (Mya) in the Late Jurassic period of Chile. Showing a combination of traits from theropods, ornithischians, and sauropodomorphs, this genus has far-reaching implications for the evolution of dinosaurs, such as whether the traditional saurischian-ornithischian split is superior or inferior to the proposed group Ornithoscelida. This however, has been contested by several other authors, who believe that the weight of evidence supports its membership within Theropoda, and possibly as a member of Tetanurae.

Under dispute

Chilesaurus diegosuarezi is an enigmatic herbivorous dinosaur of highly contested affinities, combining theropod, ornithischian, and sauropodomorph features. It was originally described as a basal tetanuran theropod (Novas and colleagues, 2015), but later analyses have recovered it as an early-diverging ornithischian within Ornithoscelida (Baron and Barrett, 2017, 2018). Because the credible hypotheses span Theropoda and Ornithischia, it is placed conservatively at Dinosauria incertae sedis.

Diagnosis

  1. Premaxilla short and deep with prominent plate-like postnarial process
  2. Teeth leaf-shaped, finely denticulate only on crown apex of erupting teeth
  3. Coracoid subquadrangular in side view with transversely thick margins
  4. Manual digit II with short pre-ungual phalanges; manual digit III atrophied
  5. Pubis fully retroverted with rod-like shaft distally unexpanded
  6. Femur lacks mediodistal crest; tibia lacks fibular crest

Species

Chilesaurus diegosuarezi Novas et al., 2015

Type species

Named for Diego Suárez, the seven-year-old who first discovered the fossils in the Aysén Region of Chile in 2004.

Holotype
SNGM-1935 , Servicio Nacional de Geológia y Minero
Material
Articulated nearly complete skeleton with skull of juvenile individual, lacking feet and most tail
Horizon
Toqui Formation, Tithonian, Late Jurassic , 149.2–143.1 million years ago
Locality
Aysén, Aysén, Chile

References

  1. Novas, F. E.; Salgado, L.; Suárez, M.; Agnolín, F. L.; Ezcurra, M. D.; Chimento, N. R.; de la Cruz, R.; Isasi, M. P.; Vargas, A. O.; Rubilar-Rogers, D. (2015). An enigmatic plant-eating theropod from the Late Jurassic period of Chile. Nature 522(7556): 331-334. Springer Science and Business Media LLC. doi:10.1038/nature14307 novas2015a
  2. Paul, G. S. (2024). The Princeton Field Guide to Dinosaurs (3rd ed.). Princeton University Press.

    Source of the mass estimate.

    paul2024a
  3. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Theropods. Princeton University Press.

    Source of the hip height estimate.

    jones2026c
  4. Baron, M. G.; Barrett, P. M. (2018). Support for the placement of Chilesaurus within Ornithischia: a reply to Müller et al. Biology Letters 14(4): 20180002. doi:10.1098/rsbl.2018.0002

    Defended Chilesaurus as an early-diverging ornithischian within Ornithoscelida, in reply to Müller and colleagues

    baron2018b
  5. Baron, M. G.; Norman, D. B.; Barrett, P. M. (2017). A new hypothesis of dinosaur relationships and early dinosaur evolution. Nature 543(7646): 501-506. doi:10.1038/nature21700

    Recovered Chilesaurus as an early-diverging ornithischian within new clade Ornithoscelida

    baron2017a