Anchiceratops
A medium-sized ceratopsid with a rectangular frill and long brow horns.
Anchiceratops is a genus of chasmosaurine ceratopsid dinosaur that lived in what is now Alberta, Canada, during the Late Cretaceous. It was a medium-sized, quadrupedal herbivore with a distinctive rectangular frill edged by coarse triangular projections. About a dozen skulls of the genus have been found, making it a notable but relatively rare ceratopsid.
Quick Facts
- Type species
- Anchiceratops ornatus
Facts from the source article.
History of discovery
The name Anchiceratops, meaning "near horned face," was given by Barnum Brown in 1914. He thought this dinosaur was a link between Monoclonius and Triceratops, especially in its skull frill. Brown’s expedition found the first fossils along Alberta’s Red Deer River in 1912. The main specimen, AMNH 5251, is the rear half of a skull with a long frill. Two other partial skulls, AMNH 5259 and AMNH 5273, were collected at the same time. All three are now in New York’s American Museum of Natural History. In 1924, Charles M. Sternberg dug up a complete skull, NMC 8535, at Morrin. He named it A. longirostris in 1929, but most scientists now consider that name a junior synonym of the only valid species, A. ornatus, which refers to the frill’s fancy edge. At least ten partial skulls are known, and their different proportions—like horn core size and frill shape—are thought to be due to age. Sternberg also found NMC 8547 in 1925. Though missing most of its skull, it is the most complete ceratopsid skeleton ever found, with a full spinal column down to the last tail vertebra. It is displayed as a half-mount in Ottawa’s Canadian Museum of Nature, using a cast of the complete skull. A few possible bonebed deposits in Alberta have also turned up, but little Anchiceratops material has been formally described.
Description
Like other ceratopsids, Anchiceratops was a quadrupedal herbivore with three horns on its face, a parrot-like beak, and a long frill extending from the back of its head. The two brow horns were longer than the single nose horn, as in other chasmosaurines. Its frill is very distinctive: rectangular in shape and edged by large epoccipitals in the form of triangular bony projections, which are exceptionally wide and coarse. The number of episquamosals varies between five and nine, with the last one very large. A pair of bony knobs on either side of the midline toward the end of the frill point sideways and vary in form and size between individuals. The parietal bone has smaller fenestrae than in other chasmosaurines. Specimen NMC 8547, on which postcranial descriptions are based, has seventy-four vertebrae: ten neck, thirteen dorsal, twelve sacral, and thirty-nine caudal. The neck is exceptionally long with four fused syncervicals, the pelvis is very long, the tail is short, and the forelimbs are robust with a large deltopectoral crest.
Paleobiology
Anchiceratops is rare compared to other ceratopsians in the area and is usually found near marine sediments in both the Horseshoe Canyon and Dinosaur Park Formations, suggesting it may have lived in estuaries where other ceratopsids did not. In 1914 Brown proposed that the distinctive frill and horn form were caused by sexual selection and intra-species recognition. In 1959 Langston suggested a semi-aquatic lifestyle, with the long snout allowing crossing of deep swamps and the heavy frill acting as a counterbalance; later paleontologists tended to reject this, but in 2012 Mallon again suggested a semi-aquatic lifestyle like a modern hippopotamus for specimen NMC 8547, explaining the limb robustness. In 1990 Lehman proposed sexual dimorphism with A. longirostris as a female, but Mallon's 2012 statistical analysis found no distinct morphs and rejected both two species and sexual dimorphism. Mallon also noted that Anchiceratops ornatus was exceptionally long-lived as a species, possibly due to decreased competition, less habitat fragmentation, or a more generalist lifestyle.
Paleoenvironment
The Horseshoe Canyon Formation, dated between 74 and 67 million years old, was deposited during the gradual withdrawal of the Western Interior Seaway. The environment included ancient meandering estuary channels, peat swamps, river deltas, floodplains, shorelines, and wetlands, with a wet and warm temperate to subtropical climate. Anchiceratops specimens are found in the upper part of Unit one, the Horsetheif member, dated to about 72–71 million years ago. It shared its paleoenvironment with dinosaurs such as Epichirostenotes curriei, Ornithomimus edmontonicus, Sphaerotholus edmontonensis, Edmontosaurus regalis, Pachyrhinosaurus canadensis, and Albertosaurus sarcophagus, with hadrosaurs dominating in number. Other vertebrates included sharks, rays, sturgeons, bowfins, gars, Aspidorhynchus, turtles, and crocodilians, though turtles and crocodilians were rare, possibly due to changes in soil drainage conditions rather than climate.
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