Mierasaurus

Mierasaurus is a turiasaurian sauropod from the Early Cretaceous Yellow Cat Member of the Cedar Mountain Formation in eastern Utah. Before its description in 2017, turiasaurs were thought to be an archaic Jurassic group largely confined to Europe. The exceptionally preserved juvenile and adult remains, including a disarticulated skull, showed that these non-neosauropods survived the Jurassic-Cretaceous boundary and dispersed into North America across land connections. Mierasaurus had heart-shaped teeth suited for clipping abrasive vegetation and stout, robust limbs. Adults grew to roughly twelve to fifteen metres long, noticeably smaller than their giant Jurassic European relatives like Turiasaurus. The genus honours Bernardo de Miera y Pacheco, the cartographer of the eighteenth-century Domínguez-Escalante expedition.

Its discovery proved that the primitive sauropod group Turiasauria survived well into the Cretaceous and crossed into North America.

Where and when

Mierasaurus lived in the Early Cretaceous, from 139 to 132 million years ago (Valanginian-Hauterivian age). Its remains come from United States, in the Cedar Mountain Formation.

The numbers

Length 14 m (estimates run from 12 to 15 m). Mass about 9.8 t. Hip height about 3.2 m. That is 7.9 human-lengths, or 1.21 of a double-decker bus. These are estimates from partial skeleton; fields marked estimated by the site are length, mass, hip height.

Compare Mierasaurus with a bus Place on the timeline