Eotriceratops

*Eotriceratops* is an extinct genus of ceratopsian dinosaur that lived in North America during the Late Cretaceous.

## History

In early August 1910, an American Museum of Natural History expedition uncovered a skeleton at the Dry Island site on the western bank of the Red Deer River of Alberta. Discovered by Barnum Brown, he was uninterested in the find as his interest was piqued by the many *Albertosaurus* in the area. In 2001, the Royal Tyrell Museum and the Canadian Museum of Nature, unaware of Brown's find, took on an expedition at the same site, rediscovering the skeleton at the hands of Glen Guthrie, the cook. Wu et al. (2007) named it "dawn three-horned face", with the specific epithet meaning "dry island" after the site. The holotype was catalogued RTMP 2002.57.5 and found in the uppermost Horseshoe Canyon Formation of the early Maastrichtian. It is a partial skeleton and much of the skull, without the mandible and including the frill margins, brow horns and nasal horn. At least 7 cervical, 5 dorsals, several ribs and ossified were collected mostly disarticulated and badly crushed due to being part of a weakly-bedded shale. In 2010, G.S. Paul reclassified it as *Triceratops xerinsularis*, but this is not universal. Other specimens from New Mexico may be included in this genus, but ceratopsid taxonomy may suggest other possible identities.

## Description

The skull is 3 meters (9.8 feet) long, suggesting an enormous animal of 8.5 meters (28-30 feet) and 10 metric tons (11 short tons). Autapomorphies are: an obliquely protruding praemaxillary process above and behind the nostril with no groove or depression on the outer side as opposed to *Triceratops* and exceptionally wide from the lateral, reaching the lower margin of the fenestra interpraemaxillaris; the epissquamosals are very elongate in the base, are flattened, spindly and touching like *Torosaurus utahensis*; a clear groove near the lower squamosal margin is seen; a vertical and slightly oblique vein groove meets another vein groove that runs horizontally on the lower front of the nasal horn core; the epijugals form an unusually sharp jugal horn; a behind-pointing and pronounced process at the upper rear of the epijugal; a depression forms a contact facet with the jugal at the top side; and a depression at the inner side created a contact facet with the quadratojugal. The snout is flattened and elongate, with depressions on the sides of the praemaxillae connected through the oval fenestra interpraemaxillaris; small rounded processes directed above and behind this feature; the nostril strut is narrow in the lateral and transversely thick with a straight rear edge; hollow-outer sided processes reach into the nostrils, but are much less excavated than *Triceratops* or *Torosaurus*; at least 35 tooth sockets in the maxilla; a low and slightly recurving nasal horn above the nostril; and with a narrow rear edge and transversely flattened point. The brow horns curved forward, estimated at ~80 centimeters (2.6 feet) long, with a vertically directed and narrow lower base, which is a juvenile trait in *Triceratops*. 3 bites above the eye near the base of the left horn were interpreted as scavenging. The squamosal has at least 5 episquamosals. Little of the parietals were preserved.

## Classification

In 2007, it was placed into Chasmosaurinae near *Triceratops*, *Nedoceratops* and *Torosaurus* as sister to the first, probably positioned lower than the other genera due to its greater age.

## References

https://en.wikipedia.org/wiki/Eotriceratops

Princeton Field Guide to Dinosaurs