The Kaiparowits Formation is a sedimentary rock formation found in the Kaiparowits Plateau in Grand Staircase–Escalante National Monument, in the southern part of Utah in the western United States. It is over 2800 feet (850 m) thick, and is Campanian in age. This Upper Cretaceous formation was formed from alluvial floodplains of large rivers in coastal southern Laramidia; sandstone beds are the deposit of rivers, and mudstone beds represent floodplain deposits. It is fossiliferous, with most specimens from the lower half of the formation, but exploration is only comparatively recent, with most work being done since 1982. It has been estimated that less than 10% of the Kaiparowits formation has been explored for fossils. The Natural History Museum of Utah has conducted most fieldwork.
Age Traditionally, the Kaiparowits Formation has been considered to be roughly equivalent in age to the northern Dinosaur Park Formation. This, combined with the differences in fauna between the two formations, has led some scientists, most notably Scott Sampson, to conclude that there was some barrier separating northern and southern Laramidia at this time. However, preliminary re-calibration of late Cretaceous formation correlations suggests that the upper part of the Kaiparowits, where many of the unique species are found, is actually younger than the Dinosaur Park, and that some Kaiparowits species may simply be the descendants of Dinosaur Park species. However, new dates reveal that this is simply an artifact of inaccurate Ar-Ar dating, and both formations had similar ages.
According to new Uranium-Lead stratigraphic data, the fossil-bearing portion of the Kaiparowits Formation dates from about 77.24 to 75.02 million years ago, with the volcaniclastic Upper Valley Member estimated to date from 73.8 to 72.8 million years ago.
Biostratigraphy The timeline below follows the re-calibrated timeline of Fowler (2017), showing species from the Kaiparowits Formation in green, and related species from Alberta in blue.
Habitat
The Kaiparowits Formation is a muddy bed that was deposited between about 77.3 to 72.8 million years ago, in the area where the Grand Staircase–Escalante National Monument of Utah is today. It is extremely fossil rich, with thousands of plants and animal fossils being preserved in amongst its sandstone and mudstone deposits. Based on plants remains including multiple vines, leaves, and branches, It was assumed by paleontologists Scott Sampson and his colleagues that Utah in the Campanian was a dense jungle bordering the Western Interior Seaway. The jungle theory would also support why almost all the animals in the Kaiparowits Formation were new species, and why the deposits were so plentiful. Without the need for herbivores to migrate to find food, and theropods to migrate after herbivores, a whole ecosystem could evolve secluded from interbreeding. The theory also supported why the dinosaurs adorned such features like the 15 horns of Kosmoceratops, they were for sexual selection.
Paleofauna
Animals present include chondrichthyans (sharks and rays), gars, bowfin, sturgeons, frogs, salamanders, turtles, lizards (including the monstersaurian Bolg amondol), crocodilians (including Deinosuchus), pterosaurs, coelurosaurian theropods such as dromaeosaurids, troodontids, and Ornithomimus velox, armored dinosaurs, the duckbill Parasaurolophus cyrtocristatus, and a variety of early mammals including multituberculates, marsupials, and insectivorans. Recent finds include large specimens of the duckbill Gryposaurus, including the species G. monumentensis, and the first described remains of the oviraptorosaurian Hagryphus giganteus.
Trace fossils are also known from the Kaiparowits, including an excellently preserved hadrosaur skin impression known from a recent analysis by Herrero and Farke.
Lizards
Lizards reported from the Kaiparowits Formation Genus Species Location Stratigraphic position Material Notes ImagesBolgWoolley, C. Henrik; Sertich, Joseph J. W.; Melstrom, Keegan M.; Irmis, Randall B.; Smith, Nathan D. (2025-06-18). "New monstersaur specimens from the Kaiparowits Formation of Utah reveal unexpected richness of large-bodied lizards in Late Cretaceous North America". Royal Society Open Science. 12 (6) 250435. Bibcode:2025RSOS...1250435W. doi:10.1098/rsos.250435. ISSN 2054-5703. PMC 12201607. PMID 40575444.B. amondol 'Fossil Ridge' Locality A fragmented skelton with articulated parts A monstersaurian lizard Odaxosaurus O. roosevelti A anguid lizard Parasaniwa P. cynochoros A palaeovaranid anguimorph
Turtles
Turtles reported from the Kaiparowits Formation Genus Species Location Stratigraphic position Material Notes ImagesBoremysB. grandisA baenidArvinachelysA. goldeniA baenid, notable for its atypical nasal structure.DenazinemysD. nodosoamiddle unit of the upper Kaiparowits FormationA baenidNeurankylusTwo speciesA baenidThescelusint.A baenidCompsemysC. victaA paracryptodiranAdocusindet., possibly several speciesAn adocidBasilemysB. nobilisA possible member of Nanhsiungchelyidae. By far the largest native turtle at about 78 centimeters in length.Helopanopliaindt.A softshell turtle
Neosuchians
Crocodilians reported from the Kaiparowits Formation Genus Species Location Stratigraphic position Material Notes ImagesBernissartia B. spMay not be Bernissartia proper, but a close cousin. It would extend the family's time range to the Campanian.Alligatoroid nov. gen.Is similar in form to Allognathosuchus.Brachychampsa B. spA new species yet to be described. Reached around 2 meters in length and is known from skull bones and a partial juvenile skeleton. Caimanine nov. gen.Known from a lower jaw fragment. Is the oldest known true caiman found.DeinosuchusD. hatcheriA very large alligatoroid, almost or over 10 meters in length.D. riograndensisA very large alligatoroid, similar in size to D. hatcheri.Goniopholid nov. gen.A new genus that exceeded 3 meters in length. Has a thin snout suited for piscivory. Leidyosuchus L. spA new species known from a partial skeleton
Ornithischians
Ankylosaurs Ankylosaurs reported from the Kaiparowits Formation Genus Species Location Stratigraphic position Material Notes ImagesAkainacephalusA. johnsoniHorse Mountain Gryposaur QuarryLower middle unitA complete skull, both mandibles, predentary, dorsal vertebrae, dorsosacral vertebrae, sacral vertebrae, caudosacral vertebrae, caudal vertebrae, dorsal ribs, a complete tail club, both scapulae, coracoid, humerus, ulna, partial ilium, femur, tibia, fibula, phalanx, partial cervical osteoderm half rings, and dorsal and lateral osteoderms.A species of ankylosaurine related to Nodocephalosaurus.AnkylosauridaeIndeterminateA partial left mandible, a disarticulated forelimb consisting of a fused scapulocoracoid, humerus, radius, ulna, metacarpals, manual phalanx and an ungual, a scapula, coracoid, cervical vertebrae, caudal vertebrae, dorsal centra vertebrae, sacral vertebrae, chevrons, a complete cervical half ring, dorsal ribs, a partial tail club, numerous osteoderms and teeth.An indeterminate ankylosaurid known from various partial specimens.Anodontosaurussp. nov.UMNH VP locality 1506Lower middle unitAn isolated partial skull lacking the left lateral-most portion and much of the anterodorsal and posteroventral palate.Described in a thesis, different from the other two Anodontosaurus species.NodosauridaeIndeterminateMiddle unitA cervical spine, numerous osteoderms, and teeth.Indeterminate nodosaurid remains.
Ceratopsians Ceratopsians reported from the Kaiparowits Formation Genus Species Location Stratigraphic position Material Notes ImagesCentrosaurinaeIndeterminateMiddle unitA partial skull and an isolated right squamosal.Also known as "Kaiparowits Centrosaurine B." Different from Nasutoceratops. ChasmosaurinaeIndeterminateDog FlatLower unitRight side of an articulated partial skull, including the ventral lacrimal, jugal, epijugal, quadratojugal, postorbital, maxilla, squamosal, and rostrolateral parietal in the region of the supratemporal fenestra.Might be a distinct taxon based on its episquamosal and squamosal morphology.KosmoceratopsK. richardsoniLower middle unitA nearly complete skull and a disarticulated skull of a subadult individual.A chasmosaurine ceratopsid with ten hook-like processes on the hind margin.NasutoceratopsN. titusiUMNH VP Locality 940Lower middle unitAn almost complete skull, a disarticulated adult skull, an isolated squamosal, a syncervical, fragmentary dorsal vertebrae, associated left forelimb and fragmentary right forelimb.A centrosaurine ceratopsid with rounded horns above its eyes.Utahceratops U. gettyi Lower to middle unit [Two] partially complete skulls, a partial postorbital consisting of the nearly complete supraorbital horncore, an isolated rostrum, premaxilla, nasal fragment, jugal, squamosal and parietal, an associated post cranium, and two immature specimens consisting of partial postorbitals with complete supraorbital horncores. A chasmosaurine ceratopsid known from adult and juvenile specimens.
Ornithopods Hadrosaurs reported from the Kaiparowits Formation Genus Species Location Stratigraphic position Material Notes ImagesBrachylophosauriniIndeterminateLower unitAn isolated jugal.The youngest example of brachylophosaurin material from Laramidia.GryposaurusG. monumentensisMiddle unitA mostly complete skull, a partial subadult skull, a partial skull roof and partial braincase, a partially articulated skeleton consisting of a portion of the skull and lower jaws, most of the dorsal, sacral, and caudal vertebral series, fragmentary ribs, scapulae, coracoid, humerus, and the entire pelvis, and a partial skeleton consisting of dorsal, sacral, and caudal vertebral series, a number of ribs, scapula, humerus, radius, ulna, and a complete pelvis.A kritosaurin saurolophine hadrosaur. Gryposaurus is the most common hadrosaur found in this formation.G. sp.Lower unit Several specimens including a virtually complete articulated skull and a fragmentary skull.May be referable to G. notabilis as the only difference is size and stratigraphy, the Kaiparowits specimens being much larger and more recent.HadrosaurinaeIndeterminateLower unitAn articulated tail, partial pelvis, and left leg.An indeterminate hadrosaurine, initially interpreted as a lambeosaurine.LambeosaurinaeIndeterminateTwo partial skeletonsSimilar to Hypacrosaurus altispinus; different from ParasaurolophusOrnithopodaIndeterminate[Six] disarticulated specimens and [one] articulated specimens, including articulated left and right feet from a single individual.One specimen shares similar foot morphology with Orodromeus, Oryctodromeus and Zephyrosaurus.Parasaurolophus"3.1 Utah, United States; 12. Kaiparowits Formation," in Weishampel, et al. (2004). Pages 579–580.P. cyrtocristatusLower to middle unit[Eight] isolated partial skulls, a partial skeleton consisting of mostly the pelvic region, fragmentary associated elements, and a juvenile specimen consisting of a partial skull and articulated skeleton.Originally identified as P. cyrtocristatus, then believed to be a new species, then tentatively referred back to P. cyrtocristatus."Skaladromeus""S. goldenii"Lower to middle unitA partial disarticulated skull and fragmentary postcranial material.An orodromine ornithopod described in a thesis.
Theropods