The Psittacosauridae were a group of ceratopsia

Ceratopsia

Ceratopsia or Ceratopia is a group of herbivorous, beaked dinosaurs which thrived in what are now North America, Europe, and Asia, during the Cretaceous Period, although ancestral forms lived earlier, in the Jurassic. The earliest known ceratopsian, Yinlong downsi, lived between 161.2 and 155.7...

n dinosaurs, which lived between 140.2 and 99.6 million years ago. The family Psittacosauridae was first named by American paleontologist Henry Fairfield Osborn

Henry Fairfield Osborn

Henry Fairfield Osborn, Sr. ForMemRS was an American geologist, paleontologist, and eugenicist.-Early life and career:...

 in 1923. The first exact definition as a clade

Clade

A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...

 was in 2005 by Paul Sereno

Paul Sereno

Paul Callistus Sereno is an American paleontologist from the University of Chicago who discovered several new dinosaur species on several continents. He has conducted excavations at sites as varied as Inner Mongolia, Argentina, Morocco, and Niger...

: the stemclade consisting of Psittacosaurus mongoliensis, Osborn 1923, and all species more closely related to Psittacosaurus than to Triceratops horridus, Marsh 1889.

The group consists of basal ceratopsians from Asia which lived during the Lower Cretaceous. The only other known genus is Hongshanosaurus

Hongshanosaurus

Hongshanosaurus is a genus of psittacosaurid ceratopsian dinosaur from the Early Cretaceous Period of eastern Asia. Although two skulls are the only fossil material described, comparisons with close relatives suggest it was a small, bipedal herbivore with a bony beak on the end of both upper and...

, which may in fact be a species of Psittacosaurus.