Bonitasaura

Bonitasaura was a medium-sized titanosaur sauropod discovered in the Bajo de la Carpa Formation of Río Negro Province, Argentina. It lived during the Santonian stage of the Late Cretaceous. The genus is distinguished by its peculiar cranial anatomy, preserved in a subadult specimen. Rather than bearing teeth along the entire margin of the lower jaw, Bonitasaura had narrow, pencil-shaped teeth clustered at the front, succeeded by a sharp bony ridge that supported a keratinous beak. This combination suggests a unique feeding mechanism wherein front teeth cropped plant shoots while the shearing beak sliced through tougher stems. Measuring around ten metres in length, Bonitasaura was relatively modest in size compared to giant contemporary titanosaurs. Its discovery revealed unsuspected diversity in the ecological specialisations and dietary adaptations of southern hemisphere sauropods.

Its lower jaw features a sharp, guillotine-like keratinous sheath behind a short row of peg-like teeth.

Where and when

Bonitasaura lived in the Late Cretaceous, from 86.3 to 83.6 million years ago (Santonian age). Its remains come from Argentina, in the Bajo de la Carpa Formation.

The numbers

Length 9.5 m (estimates run from 9 to 10 m). Mass about 3.9 t. Hip height about 2.2 m. That is 5.6 human-lengths, or 0.85 of a double-decker bus. These are estimates from partial skeleton; fields marked estimated by the site are length, mass, hip height.

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