Open Paleo

Maraapunisaurus

Carpenter, 2018

From Ute 'maraapuni' meaning 'it is very large' and Greek 'sauros' meaning 'lizard', giving the meaning 'very large lizard', named for the enormous estimated size of the specimen.

154.8–143.1 million years ago Kimmeridgian–Tithonian, Late Jurassic
Late Jurassic stages

Maraapunisaurus is a genus of sauropod dinosaur from the Late Jurassic Morrison Formation of western North America. It contains one species, Maraapunisaurus fragillimus, which was originally named Amphicoelias fragillimus. It has sometimes been estimated to be the largest dinosaur specimen ever discovered. Based on surviving descriptions of a single fossil bone, scientists have produced numerous size estimates over the years; the largest estimate M. fragillimus to have been the longest known animal at 58 meters (190 ft) in length with a mass of 150 tonnes (150 long tons; 170 short tons). However, because the only fossil remains were lost at some point after being studied and described in the 1870s, evidence survived only in contemporary drawings and field notes.

Diagnosis

  1. Extremely tall neural arch, approximately 1/3 of preserved neural spine height
  2. Unbifurcated, simply structured neural spine with spinopostzygapophyseal laminae joined to form postspinal lamina
  3. Paired pneumatic foramina pierce neural spine on each side of postspinal lamina
  4. Pneumatic camerae in neural arch dorsolateral to neural canal
  5. Festooned spinodiapophyseal lamina

Species

Maraapunisaurus fragillimus Carpenter, 2018

Type species

From Latin 'fragillimus', the superlative of 'fragilis' meaning 'very fragile', chosen by Cope to describe the extreme delicateness of the bone produced by very thin vertebral laminae.

Holotype
AMNH 5777 , American Museum of Natural History
Material
Posterior dorsal neural arch, including neural spine (minus distal apex), proximal transverse processes, both postzygapophyses
Horizon
Morrison Formation, Kimmeridgian–Tithonian, Late Jurassic , 154.8–143.1 million years ago
Locality
Cope Quarry III, Colorado, United States

References

  1. Carpenter, K. (2018). Maraapunisaurus fragillimus, N.G. (formerly Amphicoelias fragillimus), a basal Rebbachisaurid from the Morrison Formation (Upper Jurassic) of Colorado. Geology of the Intermountain West 5. Utah Geological Association. doi:10.31711/giw.v5.pp227-244 carpenter2018a
  2. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Sauropods. Princeton University Press.

    Source of the hip height estimate.

    jones2026b
  3. Mannion, P. D.; Tschopp, E.; Whitlock, J. A. (2021). Anatomy and systematics of the diplodocoid Amphicoelias altus supports high sauropod dinosaur diversity in the Upper Jurassic Morrison Formation of the USA. Royal Society Open Science 8: 210377. doi:10.1098/rsos.210377

    Gives the holotype's locality as Cope Quarry III.

    mannion2021a