Probactrosaurus

Probactrosaurus was a medium-sized herbivorous dinosaur discovered in the Early to Late Cretaceous sediments of northern China. Measuring roughly six metres long, it was approximately the weight of an adult draught horse. The dinosaur stood comfortably on all fours while browsing low foliage, but its elongate and sturdy hindlimbs suggest it could readily rear or run on two legs. Known from several well-preserved skeletons, Probactrosaurus displays a suite of transitional characteristics that position it very close to the evolutionary root of true hadrosaurids. Its snout was relatively slender compared to later broad-billed hadrosaurs, yet its jaws housed densely packed columns of replacement teeth that formed an efficient grinding mill for tough plant matter. Rozhdestvensky named the animal to highlight its evolutionary role as an apparent precursor to Bactrosaurus, making it a critical landmark in ornithopod history.

Probactrosaurus had a narrow snout and transitional dental batteries, illustrating how true duck-billed dinosaurs evolved.

Where and when

Probactrosaurus lived in the Early Cretaceous, from 105 to 96 million years ago (Albian-Cenomanian age). Its remains come from China, in the Dashuigou Formation.

The numbers

Length 6 m (estimates run from 5.5 to 6.5 m). Mass about 1.2 t. Hip height about 1.8 m. That is 3.5 human-lengths, or 0.54 of a double-decker bus. These are estimates from near-complete skeleton; fields marked estimated by the site are length, mass, first ma, last ma, hip height.

Compare Probactrosaurus with a bus Place on the timeline