Kaiparowits Formation

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 kind of 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 in fact simply be descendants of Dinosaur Park species.[1]

According to this re-calibrated stratigraphic data, the Kaiparowits dates from about 76.6 to 74.3 million years ago.[1]

The timeline below follows the re-calibrated timeline of Fowler (2017),[1] showing species from the Kaiparowits Formation in green, and related species from Alberta in blue.

The Kaiparowits Formation is a muddy bed that was deposited between about 76.6 to 74.3 million years ago,[2] 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.[3]

A Kosmoceratops disturbed from its rest by a wandering Talos in Laramidia

Animals present include chondrichthyans (sharks and rays), gars, bowfin, sturgeons, frogs, salamanders, turtles, lizards, crocodilians (including Deinosuchus),[4] 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.[5] Recent finds include large specimens of the duckbill Gryposaurus,[6] including the species G. monumentensis,[6] and the first described remains of the oviraptorosaurian Hagryphus giganteus.[7]

Trace fossils are also known from the Kaiparowits, including an excellently preserved hadrosaur skin impression known from a recent analysis by Herrero and Farke.[8]

Neosuchians

Color key Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon		Notes Uncertain or tentative taxa are in small text; crossed out taxa are discredited.

Crocodilians reported from the Kaiparowits Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Bernissartia[12]	B. sp'[12]				May not be Bernissartia proper, but a close cousin. It would extend the family's time range to the Campanian.	Bernissartia Brachychampsa Deinosuchus
Alligatoroid [13]	nov. gen.[13]				Is similar in form to Allognathosuchus.
Brachychampsa[13]	B. sp[13]				A new species yet to be described. Reached around 2 meters in length and is known from skull bones and a partial juvenile skeleton.
Caimanine[13]	nov. gen.[13]				Known from a lower jaw fragment. Is the oldest known true caiman found.
Deinosuchus	D. hatcheri[14]				A very large alligatoroid, almost 10 meters in length.
	D. riograndensis[15]				A very large alligatoroid, similar in size to D. hatcheri.
Goniopholid[13]	nov. gen.[13]				A new genus that exceeded 3 meters in length. Has a thin snout suited for piscivory.
Leidyosuchus[16]	L. sp'[16]				A new species known from a partial skeleton

Ornithischians

Color key Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon		Notes Uncertain or tentative taxa are in small text; crossed out taxa are discredited.

Ornithischians reported from the Kaiparowits Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Akainacephalus[17]	A. johnsoni	Horse Mountain Gryposaur Quarry	Lower middle unit	Complete skull and tail club, several vertebrae, osteoderms, synsacrum, hind- and forelimb elements.	A species of ankylosaurine related to Nodocephalosaurus	Akainacephalus Gryposaurus Kosmoceratops Parasaurolophus sp. nov. being attacked by Teratophoneus ("Skaladromeus") Utahceratops
Anodontosaurus[18][19]	sp. nov.	UMNH VP locality 1506	Lower middle unit	partial skull	Described in a thesis, different from the other two Anodontosaurus species.
Brachylophosaurini[20]	Indeterminate		Lower unit	jugal	The youngest example of brachylophosaurin material from Laramidia.
Centrosaurinae[21]	Indeterminate		Middle unit	partial skull	Also known as "Kaiparowits Centrosaurine B." Different from Nasutoceratops.
Chasmosaurinae[21]	Indeterminate	Dog Flat	Lower unit	partial skull	May be a separate taxon based on its episquamosal and squamosal morphology.
Gryposaurus[22]	G. monumentensis[22]		Middle unit	three skulls and an associated postcranial skeleton	A kritosaurin saurolophine hadrosaur
	G. sp.[20]		Lower unit	two skulls	May be referable to G. notabilis as the only difference is size and stratigraphy, the Kaiparowits specimens being much larger and more recent.
Lambeosaurinae[23]	Indeterminate			two partial skeletons	Similar to Hypacrosaurus altispinus; different from Parasaurolophus
Kosmoceratops[24]	K. richardsoni		Lower middle unit	two skulls	A chasmosaurine ceratopsid
Nasutoceratops[25]	N. titusi	UMNH VP Locality 940	Lower middle unit	skull, a forelimb, and some postcranial elements	A centrosaurine ceratopsid
Nodosauridae	Indeterminate		Middle unit	a spine and some associated specimens
Parasaurolophus[26]	P. cyrtocristatus[27][28]		Lower to middle unit	over a dozen skulls	Originally identified as P. cyrtocristatus, then believed to be a new species, then tentatively referred back to P. cyrtocristatus.
"Skaladromeus"[29]	"S. goldenii"		Lower to middle unit		An orodromine ornithopod described in a thesis.
Utahceratops[24]	U. gettyi		Lower to middle unit	several articulated and disarticulated specimens	A chasmosaurine ceratopsid

Theropods

Color key Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon		Notes Uncertain or tentative taxa are in small text; crossed out taxa are discredited.

Theropods reported from the Kaiparowits Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Dromaeosaurus[30]	Indeterminate			Teeth	A dromaeosaurine dromaeosaurid.	Dromaeosaurus Hagryphus Saurornitholestes Talos sampsoni Teratophoneus curriei
Hagryphus[22]	H. giganteus[22]	"The Blues"	Middle middle unit	forelimb and other elements	A caenagnathine caenagnathid
Mirarce[31]	M. eatoni	UCMP locality V93097			An avisaurid enantiornithine
Ornithomimidae[26][32]	Indeterminate[26][32]		Middle unit	partial skeleton and other elements	Probably not referable to Ornithomimus.[32] Closely related to "Ornithomimus" sedens and Rativates.[33]
Saurornitholestes[30]	Indeterminate			Teeth	A saurornitholestine or velociraptorine dromaeosaurid.
Talos[22]	T. sampsoni[22]	"The Blues	Middle middle unit		A troodont
Teratophoneus[34]	T. curriei	"The Blues"; UMNH VP Locality 597	Middle unit		A tyrannosaurine tyrannosaurid

• List of dinosaur-bearing rock formations