Kosmoceratops

Kosmoceratops (/ˌkɒzməˈsɛrətɒps/[1]) is a genus of ceratopsid dinosaur that lived in North America about 76.4–75.5 million years ago during the Late Cretaceous period. Specimens were discovered in Utah in the Kaiparowits Formation of the Grand Staircase-Escalante National Monument in 2006 and 2007, including an adult skull and postcranial skeleton and partial subadults. In 2010, the adult was made the holotype of the new genus and species Kosmoceratops richardsoni; the generic name means "ornate horned face", and the specific name honors Scott Richardson, who found the specimens. The find was part of a spate of ceratopsian discoveries in the early 21st century, and Kosmoceratops was considered significant due to its elaborate skull ornamentation. Kosmoceratops had an estimated length of 4.5 m (15 ft) and a weight of 1.2 t (1.3 short tons). As a ceratopsid, it would have been quadrupedal with a heavily constructed skeleton. It had a triangular beak with a pointed tip and a blade-like nasal horn with a flattened upper portion. While the horns above the eyes were oriented forwards or hindwards in most of its relatives, the horns of Kosmoceratops pointed up and to the sides, then downwards, ending in pointed tips. The neck frill was short from front to back, with small parietal fenestrae (openings through the frill), and ten hook-like processes on the hind margin, with eight curving forwards and two curving to the sides. With fifteen well-developed horns and horn-like structures, it possessed the most ornate skull of any known dinosaur species. Kosmoceratops was a chasmosaurine ceratopsid and was originally suggested to be closely related to Vagaceratops (which also had forward-curving processes on the back of the frill) but this has been debated, some authors finding the latter closer to Chasmosaurus. Kosmoceratops is also considered closely related to Spiclypeus, which had a similar frill.

Studies of bone histology show that Kosmoceratops grew rapidly and had an elevated metabolism, similar to modern birds and mammals. The teeth of ceratopsids were adapted to processing fibrous plants; coprolites (fossilized dung) from the Kaiparowits Formation that contain wood may have been produced by ceratopsids. The functions of ceratopsian frills and horns have been debated, including display, combat, and species recognition. The Kaiparowits Formation dates to the late Campanian age and was deposited on Laramidia, an island continent, when North America was divided at the center by the Western Interior Seaway. This environment was dominated by wetlands and supported a diverse fauna, including dinosaurs such as the chasmosaurine Utahceratops. Based in part on the relationship between Kosmoceratops and other chasmosaurines from around the same time, it has been proposed that Laramidia was divided into dinosaur "provinces" with separate endemic zones (this interpretation suggests that Kosmoceratops in the south was most closely related to the geographically separated Vagaceratops in the north), but this has been contested.Kosmoceratops is estimated to have been 4.5 m (15 ft) long and to have weighed 1.2 t (1.3 short tons). As a ceratopsid, it would have been a quadruped with a heavily constructed skeleton, a large pelvis, and a relatively shortened tail. It had long main tooth rows which formed complex slicing dental batteries containing hundreds of teeth behind an edentulous (toothless) beak.[16][2] The upper premaxillary beak of Kosmoceratops was triangular, and the frontmost rostral bone was pointed, with a tip that projected forward and downward. The nasal horncore (the bony projection from which the nose horn grew) was unusual among chasmosaurines in that it was blade-like, with a base that was elongated and narrow from side to side, and with a flattened upper portion. The nasal horncore was quadrangular in overall shape and was placed relatively far back on the snout. The naris (bony nostril opening) was different from other ceratopsids in being tall, relatively narrow from front to back, and distinctly ellipse-shaped (rather than near-circular), with a pronounced hindward inclination. The narial strut of the premaxilla (that extended from the bottom of the nasal cavity to the top) was also inclined hindward, a feature also seen in Anchiceratops and Arrhinoceratops, and the narial process that projected backwards and up from the premaxilla was a triangular prong.[2][6]

Computer rendering of a gray, quadrupedal dinosaur with many horns
Life restoration
The region around the orbits (eye sockets) was distinctive; while most chasmosaurines had supraorbital horncores (horns above the eyes) that were oriented either forward or hindward, Kosmoceratops and Utahceratops had horncores that were oriented upward and to the sides, superficially similar to those of the modern bison. Compared to the short and blunt horncores of Utahceratops, those of Kosmoceratops were more elongated and slender, curving upward then downward, ending in pointed tips. Right in front and in the middle of the orbits, the skull roof had a pronounced hump, which was present in few other ceratopsids, such as Diabloceratops. As was typical for chasmosaurines other than Chasmosaurus, it had relatively large epijugal ossifications ("cheek horns"). The lateral temporal fenestrae (openings at the sides of the skull) were tall and narrow.

The parietosquamosal neck frill (formed by the parietal and squamosal bones) of Kosmoceratops was very derived (or "advanced"), sharing several features with Vagaceratops only. This included that the frill was short from front to back, with small parietal fenestrae (openings through the frill) placed far back, and the presence of ten hook-like epiossifications (the accessory ossifications that formed the horns and lined the margins of the neck frills in ceratopsids) on the hind margin of the frill. The frill of Kosmoceratops was more extreme than that of Vagaceratops; its width was about double its length (measured across the surface of the bone), with the parietal fenestrae being much smaller and positioned farther back, and it had more elongated and distinct epiossifications on the hind margin. Though chasmosaurines have traditionally been considered the "long-frilled" ceratopsids, Kosmoceratops had the shortest frill relative to its width among chasmosaurines and the smallest parietal fenestrae relative to the total area of the frill of any ceratopsid. The squamosal bones of Kosmoceratops were strongly curved in side view, and their side margins were parallel in top view. The parietal bones did not project past the squamosals and had V-shaped hind margins, with emargination (a series of notches) spanning their entire width.

Drawing of a dinosaur skull withy many horns from above and the side
Diagram showing the skull from above and the left side
The epiossifications on the squamosal bones of Kosmoceratops became progressively larger towards the back of the neck frill. There were five well-developed epiossifications per side on the hind-margin of the frill: three forward-curved epiparietals (ep 1-3) on the parietal bone, one forward-curved epiparietosquamosal (esp) on the border between the parietal and squamosal bones, and one episquamosal (es1) on the squamosal bone that was directed to the side and downward. The forward-curving epiparietals had prominent sulci (grooves), and their bases were coalesced. With fifteen well-developed horns and horn-like structures, Kosmoceratops possessed the most ornate skull of any known dinosaurs; this included one nasal horncore, two postorbital horncores, two epijugals, and ten well-developed epiossifications at the back of the frill. The subadult specimen UMNH VP 16878 had the same number and patterns of epiossifications as the adult holotype, making it possible to distinguish the subadult growth stage of Kosmoceratops from that of Utahceratops.

   the only known species of Kosmoceratops is a blue variant with a white underbelly brown horns and beak and green eyes with osteoderms down its back