Open Paleo

Mussaurus

Bonaparte & Vince, 1979 moo-SAWR-us

From Latin 'mus' (mouse) and Greek 'sauros' (lizard); meaning 'mouse lizard', named for the small size of juvenile specimens originally known.

199.5–184.2 million years ago Sinemurian–Pliensbachian, Early Jurassic
Early Jurassic stages

Mussaurus is a genus of herbivorous sauropodomorph dinosaur that lived in southern Argentina during the Early Jurassic. It receives its name from the small size of the skeletons of juvenile and infant individuals, which were once the only known specimens of the genus. However, since Mussaurus is now known from adult specimens, the name is something of a misnomer.

Diagnosis

  1. Short and high skull with elongate frontals and parietals, very short snout
  2. Antorbital fenestra short and high, placed very near the orbit
  3. Long, very rounded cylindrical teeth (more elongated than in prosauropods)
  4. Lower jaw with thick symphysis resembling Camarasaurus rather than prosauropods
  5. Cervical vertebrae short and high, 7 mm dorsoventral height and 4 mm axial length, resembling thecodont Lagosuchus rather than prosauropods
  6. Scapula long and gracile, longer than known prosauropods
  7. Humerus proportionally longer relative to forelimbs than in known prosauropods

Species

Mussaurus patagonicus Bonaparte & Vince, 1979

Type species

Named for Patagonia, the region of southern Argentina where the holotype was discovered, with the Latin suffix '-icus' meaning 'of' or 'from'.

Holotype
PVL 4068 , Colección de Paleontologia de Vertebrados de la Fundación Instituto Miguel Lillo
Material
Most of a skeleton, skull approximately 30 mm, total estimated length 20 cm from snout to posterior end of pelvis, tail approximately 20 cm, juvenile individual.
Horizon
middle Laguna Colorada Formation, Sinemurian–Pliensbachian, Early Jurassic , 199.5–184.2 million years ago
Locality
Laguna La Colorada, Cañadón Largo farm, Santa Cruz, Argentina The Late Triassic age that Bonaparte and Vince (1979) gave these beds, later read as Norian, is not taken. Pol and colleagues (2021) note that the formation "has long been regarded as Late Triassic (Norian) in age", "mainly based on" the Dicroidium flora found near the fossil horizons, and their U–Pb dates from tuffaceous siltstones in the Mussaurus interval "assign an Early Jurassic (Sinemurian) maximum age for the Mussaurus bearing sediments" (p. 2).

References

  1. Bonaparte, J. F.; Vince, M. (1979). El hallazgo del primer nido de dinosaurios triasicos, (Saurischia, Prosauropoda), Triasico Superior de Patagonia, Argentina [The discovery of the first nest of Triassic dinosaurs (Saurischia, Prosauropoda,) from the Upper Triassic of Patagonia, Argentina]. Ameghiniana 16(1-2): 173-182.

    Gives the specimens as "recovered from Upper Triassic beds of southern Patagonia" in its original English abstract.

    bonaparte1979b
  2. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Sauropods. Princeton University Press.

    Source of the hip height estimate.

    jones2026b
  3. Pol, D.; Mancuso, A. C.; Smith, R. M. H.; Marsicano, C. A.; Ramezani, J.; Cerda, I. A.; Otero, A.; Fernandez, V. (2021). Earliest evidence of herd-living and age segregation amongst dinosaurs. Scientific Reports 11(1): 20023. Springer Science and Business Media LLC. doi:10.1038/s41598-021-99176-1

    The unit Bonaparte and Vince described as the El Tranquillo Formation; source of the U–Pb maximum age of the Mussaurus beds.

    pol2021a
  4. Hesselbo, S. P.; Ogg, J. G.; Ruhl, M.; Hinnov, L. A.; Huang, C. J. (2020). The Jurassic Period. Geologic Time Scale 2020 (Gradstein, F. M.; Ogg, J. G.; Schmitz, M. D.; Ogg, G. M., eds) 955-1021. Elsevier, Amsterdam. doi:10.1016/B978-0-12-824360-2.00026-7

    Puts the base of the Pliensbachian at 192.9 Ma, so the 192.7 Ma maximum age of the Mussaurus beds falls at the Sinemurian–Pliensbachian boundary.

    hesselbo2020a