Data from: Endocranial morphology of three early-diverging ceratopsians and implications for the behavior and the evolution of the endocast in ceratopsians

Ceratopsians underwent great changes including the shift of the locomotion
mode, enlarged horns and frills, and increased body size. These changes
are along with the changes in endocranial morphology and ecology such as
the decrease of the flocculus, the hearing range, the olfactory ratio, and
the Reptile Encephalization Quotient. However, the endocranial structures
and associated ecology of the earliest ceratopsians are still unknown.
Here, we reconstructed the endocasts of three early-diverging ceratopsians
including the Late Jurassic Yinlong, and the Early Cretaceous Liaoceratops
and Psittacosaurus. These ceratopsians display prominent flocculus, large
and separate olfactory bulbs, long and high anterior semicircular canal,
and long endosseous cochlear duct. Unlike Liaoceratops and Psittacosaurus,
Yinlong exhibits relatively stocky semicircular canals and small
flocculus. In Ceratopsia, the evolutional patterns of the endocast include
the merging and narrowing of the olfactory bulbs, the disappearing
flocculus, the reduction of the anterior semicircular canal, the
increasing of the angle between two vertical semicircular canals, and the
shortening of the cochlear duct. The endocranial structures suggest
early-diverging ceratopsians had a high olfactory acuity and were adapted
to hearing high frequencies, unlike the condition of late-diverging
ceratopsians with lower olfactory acuity and hearing frequency. Reptile
Encephalization Quotient suggests that Yinlong and Psittacosaurus were
more encephalized than most extant reptiles and late-diverging
ceratopsians. The angle of the lateral semicircular canal suggests that
heads in ceratopsians display a transition from an upward posture to a
downward posture. The relatively upward head posture indicates that
early-diverging ceratopsians could feed more selectively such as to eat
some leaves.