Kosmoceratops is known from the Kaiparowits Formation of Utah, which dates to the late Campanian age of the Late Cretaceous epoch, and occurs in a stratigraphic range spanning the upper part of its lower unit to the upper part of its middle unit, in sediments dating to 76.4–75.5 million years ago.
The formation was deposited in the southern part of a basin (the Western Interior Basin) on the eastern margin of a landmass known as Laramidia (an island continent consisting of what is now western North America) within 100 km (62 mi) of the Western Interior Seaway, a shallow sea in the center of North America that divided the continent (the eastern landmass is known as Appalachia).
The basin was broad, flat, crescent-shaped, and bounded by mountains on all sides except the Western Interior Seaway at the east.
The formation represents an alluvial to coastal plain setting that was wet, humid, and dominated by large, deep channels with stable banks and perennial wetland swamps, ponds, and lakes.
Rivers flowed generally west across the plains and drained into the Western Interior Seaway; the Gulf Coast region of the United States has been proposed as a good modern analogue (such as the current day swamplands of Louisiana).
The formation preserves a diverse and abundant range of fossils, including continental and aquatic animals, plants, and palynomorphs (organic microfossils).

Other ornithischian dinosaurs from the Kaiparowits Formation include ceratopsians such as the chasmosaurine Utahceratops, the centrosaurine Nasutoceratops (and possibly a second yet unnamed centrosaurine), indeterminate pachycephalosaurs, the ankylosaurid Akainacephalus, an indeterminate nodosaurid, the hadrosaurs Gryposaurus and Parasaurolophus, and an indeterminate, basal neornithischian.
Theropods include the tyrannosaurid Teratophoneus, the oviraptorosaur Hagryphus, an unnamed ornithomimid, the troodontid Talos, indeterminate dromaeosaurids, and the bird Avisaurus.
Other vertebrates include crocodiles (such as Deinosuchus and Brachychampsa), turtles (such as Adocus and Basilemys), pterosaurs, lizards, snakes, amphibians, mammals, and fishes.
The two most common groups of large vertebrates in the formation are hadrosaurs and ceratopsians (the latter representing about 14 percent of associated vertebrate fossils), which may either indicate their abundance in the Kaiparowits fauna or reflect preservation bias (a type of sampling bias) due to these groups also having the most robust skeletal elements.
Eggs from dinosaurs, crocodiles, and turtles have also been found.
The swamps and wetlands were dominated by up to 30 m (98 ft) cypress trees, ferns, and aquatic plants including giant duckweed, water lettuce, and other floating angiosperms.
Better-drained areas were dominated by forests of up to 10–20 m (33–66 ft) dicot trees and occasional palms, with an understory including ferns.
Well-drained areas further away from wet areas were dominated by conifers up to 30 m (98 ft), with an understory comprising cycads, small dicot trees or bushes, and possibly ferns.

In 2010, paleontologist Michael A. Getty and colleagues examined the taphonomy of the holotype and the subadult specimen UMNH VP 16878 and the sedimentological circumstances under which they were preserved.
The more or less articulated holotype specimen was found in a silty sandstone channel lithofacies (the rock record of a sedimentary environment), which is consistent with its carcass having been washed into a river channel, then buried quickly.
The limbs and part of the tail may have been lost to scavengers or rot prior to the carcass being deposited.
The parts missing from the left side of the skull were lost to erosion before the discovery.
Since much of the skeleton was still under preparation at the time, researchers were unable to examine it for signs of predation and scavenging.
The subadult specimen UMNH VP 16878 was found scattered across an area of 3 m² (32 sq ft), and the high degree of disarticulation and broken parts indicate that the specimen was skeletonized and decomposed before its bu
Kosmoceratops is known from the Kaiparowits Formation of Utah, which dates to the late Campanian age of the Late Cretaceous epoch, and occurs in a stratigraphic range spanning the upper part of its lower unit to the upper part of its middle unit, in sediments dating to 76.4–75.5 million years ago. The formation was deposited in the southern part of a basin (the Western Interior Basin) on the eastern margin of a landmass known as Laramidia (an island continent consisting of what is now western North America) within 100 km (62 mi) of the Western Interior Seaway, a shallow sea in the center of North America that divided the continent (the eastern landmass is known as Appalachia). The basin was broad, flat, crescent-shaped, and bounded by mountains on all sides except the Western Interior Seaway at the east. The formation represents an alluvial to coastal plain setting that was wet, humid, and dominated by large, deep channels with stable banks and perennial wetland swamps, ponds, and lakes. Rivers flowed generally west across the plains and drained into the Western Interior Seaway; the Gulf Coast region of the United States has been proposed as a good modern analogue (such as the current day swamplands of Louisiana). The formation preserves a diverse and abundant range of fossils, including continental and aquatic animals, plants, and palynomorphs (organic microfossils).
Other ornithischian dinosaurs from the Kaiparowits Formation include ceratopsians such as the chasmosaurine Utahceratops, the centrosaurine Nasutoceratops (and possibly a second yet unnamed centrosaurine), indeterminate pachycephalosaurs, the ankylosaurid Akainacephalus, an indeterminate nodosaurid, the hadrosaurs Gryposaurus and Parasaurolophus, and an indeterminate, basal neornithischian. Theropods include the tyrannosaurid Teratophoneus, the oviraptorosaur Hagryphus, an unnamed ornithomimid, the troodontid Talos, indeterminate dromaeosaurids, and the bird Avisaurus. Other vertebrates include crocodiles (such as Deinosuchus and Brachychampsa), turtles (such as Adocus and Basilemys), pterosaurs, lizards, snakes, amphibians, mammals, and fishes. The two most common groups of large vertebrates in the formation are hadrosaurs and ceratopsians (the latter representing about 14 percent of associated vertebrate fossils), which may either indicate their abundance in the Kaiparowits fauna or reflect preservation bias (a type of sampling bias) due to these groups also having the most robust skeletal elements. Eggs from dinosaurs, crocodiles, and turtles have also been found. The swamps and wetlands were dominated by up to 30 m (98 ft) cypress trees, ferns, and aquatic plants including giant duckweed, water lettuce, and other floating angiosperms. Better-drained areas were dominated by forests of up to 10–20 m (33–66 ft) dicot trees and occasional palms, with an understory including ferns. Well-drained areas further away from wet areas were dominated by conifers up to 30 m (98 ft), with an understory comprising cycads, small dicot trees or bushes, and possibly ferns.
In 2010, paleontologist Michael A. Getty and colleagues examined the taphonomy of the holotype and the subadult specimen UMNH VP 16878 and the sedimentological circumstances under which they were preserved. The more or less articulated holotype specimen was found in a silty sandstone channel lithofacies (the rock record of a sedimentary environment), which is consistent with its carcass having been washed into a river channel, then buried quickly. The limbs and part of the tail may have been lost to scavengers or rot prior to the carcass being deposited. The parts missing from the left side of the skull were lost to erosion before the discovery. Since much of the skeleton was still under preparation at the time, researchers were unable to examine it for signs of predation and scavenging. The subadult specimen UMNH VP 16878 was found scattered across an area of 3 m² (32 sq ft), and the high degree of disarticulation and broken parts indicate that the specimen was skeletonized and decomposed before its bu
Kosmoceratops