Ceratopsia
Herbivorous, beaked dinosaurs with horns and frills.
Ceratopsia, or Ceratopia, meaning "horned faces" in Greek, is a group of herbivorous, beaked dinosaurs that flourished across what is now North America, Asia, and Europe during the Cretaceous Period. Their earliest known ancestor, *Yinlong downsi*, lived between 161.2 and 155.7 million years ago in the Late Jurassic of Asia. The last ceratopsian species, *Triceratops prorsus*, perished in the Cretaceous–Paleogene extinction event. *Triceratops* remains the most famous ceratopsian to the public. Traditionally, ceratopsian genus names end in "-ceratops," though exceptions exist. The genus *Ceratops* itself gave the group its name, but it is now considered a *nomen dubium* because its fossils lack unique distinguishing traits.
Early members, such as *Psittacosaurus*, were small and bipedal. Later forms, including the ceratopsids *Centrosaurus* and *Triceratops*, evolved into very large quadrupeds with elaborate facial horns and frills extending over the neck. These frills may have protected the neck from predators, aided in display, thermoregulation, or anchored large chewing muscles. Ceratopsians ranged greatly in size. Their skulls are easily recognized by the rostral bone, a toothless ossification unique to the group, located on the tip of the upper jaw. This bone, named by Othniel Charles Marsh, mirrors the predentary bone of the lower jaw and forms a parrot-like beak. The jugal bones below the eye are prominent, flaring outward to give the skull a triangular shape from above, a shape accentuated in later species by the rearward extension of the parietal and squamosal bones into the neck frill.
The frills of ceratopsids are bordered by epoccipital bones, which begin as separate bones and fuse during growth to the squamosal or parietal bones. These ornamental bones likely helped differentiate species. They were broadly different between short-frilled centrosaurines and long-frilled chasmosaurines, being elliptical with constricted bases in the former and triangular with wide bases in the latter. In centrosaurines like *Centrosaurus*, *Pachyrhinosaurus*, and *Styracosaurus*, these bones became long spikes or hooks. *Triceratops* had a coarse sawtooth fringe of broad triangular epoccipitals. The term epoccipital was coined by Marsh in 1889.
The first ceratopsian remains were discovered during F.V. Hayden’s surveys. Teeth from an 1855 Montana expedition were
- Last known species
- Triceratops prorsus, became extinct 66 million years ago
- Time period
- Late Jurassic to Late Cretaceous
- Geographic range
- North America, Asia, Europe
- Distinctive feature
- Rostral bone, an edentulous ossification unique to ceratopsians
Quick Facts
- Taxon
- Ceratopsia
- Type Species
- Ceratops montanus
- Type Species Authority
- Marsh, 1888
Facts from the source article.
Lore & Background
The first ceratopsian remains known to science were discovered during U.S. Geological and Geographical Surveys led by geologist F.V. Hayden. Teeth found in 1855 in Montana were initially assigned to hadrosaurids, but were later recognized as ceratopsian. In 1872, Fielding Bradford Meek found giant bones in Wyoming, leading Edward Drinker Cope to excavate a partial skeleton he named *Agathaumas sylvestris*, noting it differed from known dinosaurs despite lacking a skull. Cope later named *Monoclonius* from fossils found in Montana in 1876, which provided the first evidence of ceratopsid horns and frills, though he initially misinterpreted the frill bone as part of the breastbone. In 1888 and 1889, Othniel Charles Marsh described the first well-preserved horned dinosaurs, *Ceratops* and *Triceratops*, and in 1890 classified them in the family Ceratopsidae and order Ceratopsia. This prompted Cope to reexamine his specimens, realizing *Triceratops*, *Monoclonius*, and *Agathaumas* formed a single group, which he named Agathaumidae in 1891. Cope then redescribed *Monoclonius* as a horned dinosaur with a large nasal horn, two smaller brow horns, and a large frill.
Reader's Guide
The group is defined in clade-based taxonomy as the largest clade containing Ceratops montanus and Triceratops horridus but not Pachycephalosaurus wyomingensis. Early members like Psittacosaurus were small bipeds, while later ceratopsids became large quadrupeds with horns and frills. The frills may have served for protection, display, thermoregulation, or muscle attachment. Epoccipital bones surrounded the frills of ceratopsids and were ornamental, differing between short-frilled centrosaurines and long-frilled chasmosaurines. The name Ceratopsia is linguistically incorrect, with Ceratopia being technically correct, but the former remains in common use.
Did You Know?
- The rostral bone on the upper jaw is a toothless ossification unique to ceratopsians.
- Epoccipital bones, which surrounded the neck frills of ceratopsids, were ornamental and began as separate bones that fused during growth.
- The name Ceratopsia is derived from Greek words meaning 'horn' and 'face'.
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