Auroraceratops

Discovery and species

The story of Auroraceratops begins with a long history of fossil hunting in China's Gansu Province. The first dinosaur finds there came during the Sino-Swedish Expedition of 1930 to 1931, which uncovered the early ceratopsian Microceratops sulcidens, a species now considered questionable. Sporadic bone discoveries followed in the Houhongquan Basin during the 1960s and in the Gongpoquan Basin in 1986. A reconnaissance trip by the China-Canada Dinosaur Project visited the Gongpoquan Basin in 1988, but no further work happened until the Sino-Japanese Silk Road Dinosaur Expedition of 1992 and 1993.

Led by Chinese paleontologist Dong Zhiming of the IVPP and Japanese paleontologist Yoichi Azuma of the FPDM, this project found the early ceratopsian Archaeoceratops, based on a skull and two partial skeletons, along with many other unique genera that make up the Mazongshan Dinosaur Fauna. Later, the Sino-American Mazongshan Dinosaur Project ran from 1997 to 2000, involving the University of Pennsylvania, Carnegie Museum of Natural History, and the IVPP.

In 1999, team members identified the Yujingzi Basin as a promising fossil site, and the first dinosaur fossils there were found in 2000 by a group that included Chinese paleontologist You Hailu of the CAGS. You then began working with Chinese paleontologist Li Daqing of the FRDC of Gansu Province in 2004, starting digs in the Yujingzi Basin and continuing work in the Gongpoquan Basin. That same year, FRDC fieldwork in the Gongpoquan Basin recovered a well-preserved early ceratopsian skull, cataloged as CAGS IG-2004-VD-001.

Noticing clear anatomical differences from Archaeoceratops, You and his colleagues named the new species Auroraceratops rugosus in 2005, making that skull the holotype. The genus name uses the Latin word aurora, meaning "dawn," as a double-entendre: it refers both to the animal's status as an early ceratopsian and to Dawn Dodson, wife of co-author Peter Dodson. The species name rugosus points to the rough, rugose texture seen on the skull and jaws.

Description

Unlike most other neoceratopsians with long, narrow snouts, Auroraceratops has a shorter, wider one. Its 20 cm skull is flat and wide, with at least two pairs of striated fang-like teeth in the premaxillae. Paired rugose areas, likely covered in keratin in life, occur in front of the eyes and on the jugal, with corresponding areas on the lower jaw. Some specimens show variation in skull morphology, possibly due to intra-specific variation, sexual dimorphism, or taphonomy. Bone beds of 74 articulated individuals (1869 skeletal elements) indicate rapid burial inside burrows, based on curled-up preservation and lack of bone weathering. A 2019 post-cranial analysis showed Auroraceratops walked bipedally, with an estimated length of 1.25 m, hip height of 44 cm, and body mass of 15.5 kg.

Paleoecology

Auroraceratops is a key component of the Mazongshan Dinosaur Fauna of the Early Cretaceous Xinminbao Group, distributed between the Gongpoquan and Yujingzi basins of Gansu Province. The fauna dates from the mid-Aptian to the early Albian, within the Xiagou and Zhonggou Formations. Eleven dinosaur genera are known from the Mazongshan Dinosaur Fauna, none found elsewhere except dubious genera named by Birger Bohlin. Theropods include the tyrannosauroid Xiongguanlong, the ornithomimosaur Beishanlong, and the therizinosaur Suzhousaurus.

Additional ornithomimosaur specimens belong to Beishanlong and a new unnamed taxon, and the uncertain therizinosaur 'Nanshiungosaurus' bohlini is also known. Two sauropods, the somphospondylans Gobititan and Qiaowanlong, are present. Four early hadrosauroids are known: Equijubus, Gongpoquansaurus, Xuwulong, and Jintasaurus. Auroraceratops is one of two neoceratopsian genera, the other being Archaeoceratops.

Auroraceratops is known only from red-colored beds at the bottom of the Zhonggou Formation, found alongside Archaeoceratops oshimai, Beishanlong, the unnamed ornithomimosaur, Suzhousaurus, and 'N.' bohlini. Sedimentary features indicate a seasonally arid environment.