Open Paleo

Mierasaurus

Royo-Torres et al., 2017 me-EHR-ah-SOR-us

Named for Bernardo de Miera y Pacheco, an eighteenth-century Spanish cartographer and explorer of the American Southwest, combined with Greek 'sauros' meaning 'lizard'.

137.1–132.6 million years ago Valanginian, Early Cretaceous
Early Cretaceous stages

Mierasaurus is an extinct genus of sauropod dinosaur from the Early Cretaceous of Utah, United States. The taxon was first described and named in 2017 by Rafael Royo-Torres and colleagues, from a mostly complete skeleton including a disarticulated partial skull and mandible, teeth, multiple vertebrae from along the length of the body, both scapulae, radius and ulna bones, a left manus, a complete pelvis, both femora and the entire left hindlimb. Additionally, they referred a lower jaw and femur from juvenile individuals, which were found nearby, to the genus. Collectively, Mierasaurus is among the most completely known North American sauropods. The genus name honors Bernardo de Miera y Pacheco, the first European scientist to enter what is now Utah. The type species for Mierasaurus is Mierasaurus bobyoungi, named after Robert Glen Young, a paleontologist who researched the Early Cretaceous of Utah.

Diagnosis

  1. Otosphenoidal ridge extends from anterior surface of paroccipital process near its ventral margin and restricted to medialmost part of latter process
  2. Occipital condyle has pair of rounded ridges extending dorsoventrally on either lateral face of condylar articular surface
  3. Atlantal intercentrum bears pair of depressions in medial surface facing posteromedially, each receiving anterolateral margin of odontoid process
  4. Cervical ribs bear ridge or bulge on lateral surface of tuberculum immediately posterior to base of anterior process
  5. Lateral depression on distal ramus of haemal arches
  6. Metacarpal I longer than metacarpal IV
  7. Very short ischium compared to pubis (ischium:pubis length ratio 0.75)
  8. Fourth trochanter placed in proximal part of femur
  9. Femur with subequal distal condyles
  10. Pedal unguals 2 and 3 compressed dorsoventrally

Species

Mierasaurus bobyoungi Royo-Torres et al., 2017

Type species

Named for Robert ('Bob') Young, a paleontologist who conducted underappreciated research on the Early Cretaceous geology of Utah.

Holotype
UMNH.VP.26004 , Utah Museum of Natural History
Material
Partial skeleton: disarticulated cranial and postcranial elements including partial skull and jaw, teeth, atlas, 8 cervical vertebrae, 11 cervical ribs, 11 dorsal vertebrae, 6 dorsal ribs, 6 sacral ribs, 15 caudal vertebrae, two chevrons, scapula, radius, ulna, manus, complete pelvic elements, both femora, tibia, fibula, astragalus, and pes.
Horizon
lower Yellow Cat Member, Cedar Mountain Formation, Valanginian, Early Cretaceous , 137.1–132.6 million years ago
Locality
Doelling's Bowl Bonebed, Utah, United States

References

  1. Royo-Torres, R.; Upchurch, P.; Kirkland, J. I.; DeBlieux, D. D.; Foster, J. R.; Cobos, A.; Alcalá, L. (2017). Descendants of the Jurassic turiasaurs from Iberia found refuge in the Early Cretaceous of western USA. Scientific Reports 7(1). Springer Science and Business Media LLC. doi:10.1038/s41598-017-14677-2 royo-torres2017b
  2. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Sauropods. Princeton University Press.

    Source of the body length, mass, and hip height estimates.

    jones2026b