# List of marginocephalian type specimens

This list of specimens is a comprehensive catalogue of all the type specimens and their scientific designations for each of the genera and species that are included in the clade marginocephalia.
Marginocephalia is a clade of ornithischian dinosaurs that includes some of the most well-known Mesozoic animals, such as Triceratops and Pachycephalosaurus. The group is united by, and is named for, the presence of a bony margin formed mostly from the parietal and squamosal bones at the posterior end of the skull. Although the first marginocephalian known to scientists, Agathaumas, was described in 1872 by Edward Drinker Cope, the clade itself was not recognized until the latter part of the 20th century when Paul Sereno first united the two major groups, ceratopsians and pachycephalosaurians into a single clade.
Marginocephalians first appeared in the Jurassic period as small bipedal animals. However, they saw an apparent increase in diversity during the Early Cretaceous period which culminated in the emergence of megafaunal forms by the end of the period that weighed in excess of five metric tons. Most of their diversity is known from North America and Asia, with a few remains attributed to the group from Europe, South America, and Australia.

## Scope and terminology

This list will include the type fossils of each marginocephalian species. In paleontology, a type specimen is one which is definitionally a member of a biological taxon. Additional specimens can only be "referred" to these taxa if an expert deems them sufficiently similar to the type and publishes that opinion in the scientific literature.
There is no complete, canonical list of all dinosaur taxa or holotype specimens. Attempts are regularly published in the form of books, such as the Princeton Field Guide to Dinosaurs by Gregory Paul and Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages by Thomas Holtz and Luis Rey. Where appropriate, The Paleobiology Database and Fossilworks, which are both online databases of named fossil taxa, are used to supplement the entries from published encyclopedias which are missing or data-deficient.

### Type system

Types are also used to diagnose higher-level taxa than an individual. One individual might represent the "type specimen" of a particular species. This species would in turn represent the "type species" of a particular genus, unless it is referred to a previously described genus. Most dinosaur genera are monospecific, therefore most type specimens are also the type species of their respective genera. On this list, the type species of a genus is only noted when it belongs to a genus with multiple referred species, such as Psittacosaurus or Chasmosaurus. Furthermore, when an animal is different enough from its close relatives that it is given its own family, it is conventional in dinosaur systematics to name a family after the first described, most famous, or most abundant genus assigned to it. Therefore, on this list, the type species of any type genus for a family or sub-family level taxon is also noted when appropriate.
There are several different varieties of type specimen when referring to fossil animals:
* Holotype: This is the most common and simplest form of type specimen. A holotype is the first material of a fossil specimen that is described in the scientific literature. In order to qualify as a true holotype, all of the fossils of the type must belong to the same individual animal. All type specimens on this list are holotypes, unless otherwise indicated.
* Paratype(s): These are described in the same publication as the holotype. A paratype is designated when the fossil material is diagnostic enough to belong to the same species as the holotype, but it is not from the same individual animal. In these cases, the holotype and paratype(s) are collectively called the "type series" for that taxon. On this list, paratypes are noted in the same entry as their associated holotype.
* Neotype: When a holotype specimen is lost, destroyed, or otherwise unable to be studied further by scientists, a new type specimen for that taxon is required in order to identify future material. On this list, neotypes are only given their own entries when the holotype was never formally given a specimen number, otherwise they are noted in the entry for the holotype.
* Syntype(s): This is a type series in which no single specimen is selected to serve as a holotype, nor are any designated as paratypes. This is typically done if the fossil material is believed to be from multiple animals, but none of the individual animals were well-preserved enough to provide a complete list of diagnostic characters. These are also sometimes called "cotypes" in publications, although this is discouraged by the ICZN.
* Lectotype: When a single type specimen from a series of syntypes is designated as the new primary type specimen in a subsequent publication, this is considered to be a lectotype. On this list, lectotypes are given their own entries.
* Paralectotype(s): When a lectotype is designated from a series of syntypes, the remaining syntypes become paralectotypes as part of a reorganized type series. On this list, paralectotypes are noted alongside the list entry for the lectotype of their respective series.
* Plastotype: Sometimes, if a cast of a type specimen is made and the original type specimen is lost or destroyed, the cast can be used for the purposes of diagnostic referral to a taxon. Plastotypes are only given their own entries on this list if the holotype was not given a specimen number. Otherwise, they are noted alongside the entry for the holotype.
All name-bearing type specimens (i.e. holotypes, lectotypes, neotypes, and syntypes) have unique entries on this list, and non-name-bearing types (i.e. paratypes, paralectotypes, and topotypes) are noted alongside their name-bearing counterpart.

### Validity

Some described species are later determined to be invalid by subsequent scientific publications. However, invalid species are sometimes resurrected, such as in the case of Brontosaurus, and sometimes the validity of a species can be controversial among researchers (e.g. the case of Torosaurus and Triceratops). For the purposes of neutrality and completeness, all described species and genera of marginocephalians are included, even those that have been subsequently considered invalid by subsequent scientific publications.
Naming conventions and terminology follow the International Code of Zoological Nomenclature (ICZN). Technical terms used include:
* Junior synonym: A name which describes the same taxon as a previously published name. If two or more taxa are formally designated and the type specimens are later assigned to the same taxon, the first to be published (in chronological order) is the senior synonym, and all other instances are junior synonyms. Senior synonyms are generally used, except by special decision of the ICZN, but junior synonyms cannot be used again, even if deprecated. Junior synonymy is often subjective, unless the genera described were both based on the same type specimen.
* Nomen dubium (Latin for "dubious name"): A name describing a fossil with no unique diagnostic features. This can be an extremely controversial designation, and as such, they are only notated when their supposedly dubious status has been formally published. Furthermore, if the scientific community has yet to reach a consensus on the validity of a name or taxon, the ongoing nature of the controversy will be stated.
* Nomen nudum (Latin for "naked name"): A name that has appeared in print but has not yet been formally published by the standards of the ICZN. Nomina nuda (the plural form) are invalid, and are not included on this list.
* Preoccupied name: A name that is formally published, but which has already been used for another taxon. This second use is invalid (as are all subsequent uses) and the name must be replaced.

### Omissions

Some taxa of marginocephalians are not included on this list. Nomina nuda are not included because a type does not become recognized by the ICZN until it is published in a scientific journal with a full description.
Some misidentified taxa are also not included so long as there is a scientific consensus with regard to the specimen in question. If a specimen is later referred to a taxon outside marginocephalia, it is not included on this list. However, specimens that are identified as marginocephalians in publications subsequent to their initial description are included under the name they are given within marginocephalia. For example, Pachycephalosaurus was originally described as a species of the theropod genus Troodon. This is noted where appropriate, but there is no entry on the list under the name Troodon wyomingensis because the specimen itself is now referred to a taxon within marginocephalia.
Referred taxa are only included on the list as separate entries when their initial description includes a unique type specimen (e.g. Triceratops obtusus or Dracorex hogwartsia).

## List of specimens

* Binomial name: All animals species are given a unique binomial name, typically consisting of Latin or Greek words which are used to formally and scientifically identify each species.
* Catalogue number: In most museum collections, each fossil specimen will be given a unique catalogue number which is published with the description of the fossils after they are prepared. This serves as a formal name for every single described fossil so that authors are able to refer to individual fossil discoveries in the scientific literature by name.
* Institution: Most published fossils are stored in museum collections or at universities. This is also true of type specimens, many of which are on display in museums around the world. If a type specimen has been lost, the last known location of the type is listed.
* Age: The geological stage from which the specimen was recovered is listed, when it is known. The exact age of some geological formations is not known. If this is the case, a range of possible ages is given.
* Unit: Most fossils are recovered from named geologic formations (e.g. the Morrison Formation or the Hell Creek Formation). When this is not the case, a city or landmark near the locality from which the fossil was recovered is listed.
* Material: The vast majority of fossils do not preserve the complete skeleton of an animal. In these cases, the specific bones which are fossilized have been listed.
* Notes: Other general information, such as the validity status of the taxon in question, or any other material in the type series may be listed here.
| Binomial Name | Catalogue Number | Institution | Age | Unit | Material | Notes | Images |
| Achelousaurus horneri | MOR 485 | Museum of the Rockies | Late Campanian | Upper Two Medicine Formation, Alberta | Mostly complete skull | | The holotype on display in Colorado |
| Acrotholus audeti | TMP 2008.045.0001 | Royal Tyrell Museum | Santonian | Milk River Formation, Alberta | Frontoparietal skull dome | | |
| Agathaumas sylvestris | AMNH 4000 | American Museum of Natural History | Late Maastrichtian | Lance Formation, Wyoming | Numerous vertebrae, a partial pelvis, and several ribs | Nomen dubium, generally considered a chimera or synonymous with Triceratops | Illustration of the holotype material |
| Agujaceratops mariscalensis | UTEP P.37.7.086 | Texas Memorial Museum | Late Campanian | Aguja Formation, Texas | Partial skull | Type species of Agujaceratops, originally described as Chasmosaurus mariscalensis | The holotype on display in Austin |
| Agujaceratops mavericus | TMM 43098-1 | Texas Memorial Museum | Late Campanian | Aguja Formation, Texas | Nearly complete skull | | |
| Ajkaceratops kozmai | MTM V2009.192.1 | Hungarian Natural History Museum | Santonian | Csehbánya Formation, Hungary | Partial beak and rostrum | | The holotype without the dentary |
| Alaskacephale gangloffi | UAM AK-493-V-001 | University of Alaska Museum | Early Maastrichtian | Prince Creek Formation, Alaska | | | |
| Albalophosaurus yamaguchiorum | SBEI 176 | Hakusan City Board of Education | Barremian | Kuwajima Formation, Japan | Incomplete skull and jawbones | May be an ornithopod or some other type of ornithischian | |
| Albertaceratops nesmoi | TMP.2001.26.1 | Royal Tyrrell Museum | Middle Campanian | Oldman Formation, Alberta | Complete skull and postcranial fragments | | Holotype skull without the postcranial elements |
| Amtocephale gobiensis | MPC-D 100/1203 | Mongolian Natural History Museum | Uncertain (Albian to Santonian?) | Bayan Shireh Formation, Mongolia | Partial skull dome | | |
| Anchiceratops longirostris | NMC 8535 | Canadian Museum of Nature | Early Maastrichtian | Horseshoe Canyon Formation, Alberta | Complete skull | Nomen dubium, may be synonymous with A. ornatus or may represent sexual dimorphism | |
| Anchiceratops ornatus | AMNH 5251 | American Museum of Natural History | Early Maastrichtian | Horseshoe Canyon Formation, Alberta | Partial skull with intact frill | Type species of Anchiceratops | The holotype in lateral view |
| Aquilops americanus | OMNH 34557 | Sam Noble Oklahoma Museum of Natural History | Middle Albian | Cloverly Formation, Montana | Mostly complete skull | | The holotype skull from multiple views |
| Archaeoceratops oshimai | IVPP V11114 | Institute of Vertebrate Paleontology and Paleoanthropology | Early Aptian | Digou Formation, Xinminbao Group, Gansu | Skull, vertebrae, pelvis, and partial foot | Type species of Archaeoceratops | The holotype skull from multiple views |
| Archaeoceratops yujinziensis | CAGS-IG-VD-003 | Chinese Academy of Geological Sciences | Late Aptian | Xiagou Formation, Gansu | Vertebrae and partial hindlimb | | |
| Arrhinoceratops brachyops | ROM 796 | Royal Ontario Museum | Early Maastrichtian | Horseshoe Canyon Formation, Alberta | Mostly complete skull | | The holotype on display in Ontario |
| Asiaceratops salsopaludalis | CCMGE 9/12457 | Saint Petersburg State University | Early Cenomanian | Khodzhakul Formation, Uzbekistan | Partial maxilla | Type species of Asiaceratops, may be a nomen dubium | |
| Asiaceratops sulcidens | No catalogue number | | Uncertain (Aptian to Albian?) | Xinminbao Group, Gansu | Teeth, centra, and hindlimb elements | May be a nomen dubium | |
| Auroraceratops rugosus | IG-2004-VD-001 | Chinese Academy of Geological Sciences | Aptian | Xinminbao Group, Gansu | Nearly complete skull | The holotype is known to be a subadult | A reconstruction of the holotype in situ with a hypothetical postcranial skeleton |
| Avaceratops lammersi | ANSP 15800 | Academy of Natural Sciences of Drexel University | Late Campanian | Judith River Formation, Montana | Partial skull, shoulder, most of the forelimbs, and some vertebrae | Maturation level of the holotype is unresolved, may represent a juvenile, but this is uncertain | Cast of the holotype with missing elements filled in for display |
| Bagaceratops rozhdestvenskyi | ZPAL MgD-I/126 | Polish Academy of Sciences | Early Maastrichtian | Barun Goyot Formation, Mongolia | Mostly complete skull | Generally regarded as the senior synonym for Gobiceratops, Lamaceratops, Magnirostris, and Platyceratops | |
| Bainoceratops efremovi | PIN 614-33 | Russian Academy of Sciences | Campanian | Djadochta Formation, Mongolia | Dorsal vertebrae | | |
| Beg tse | IGM 100/3652 | Mongolian Academy of Sciences | Uncertain (Albian?) | Ulaanoosh Formation, Mongolia | Skull | | Holotype with skull bones labeled |
| Bisticeratops froeseorum | NMMNH P-50000 | New Mexico Museum of Natural History | Late Campanian | Kirtland Formation, New Mexico | Mostly complete skull | | Diagram of the holotype material |
| Brachyceratops montanensis | USNM 7951 | Smithsonian Institution | Campanian | Two Medicine Formation, Montana | Mostly complete skull | May be a nomen dubium, holotype is known to be a juvenile and has been suggested to belong to a juvenile individual of the contemporaneous Styracosaurus or Rubeosaurus | Holotype skull mounted on a hypothetical skeleton |
| Bravoceratops polyphemus | TMM 46015-1 | Texas Memorial Museum | Late Maastrichtian | Javelina Formation, Texas | Numerous skull fragments | May or may not be a nomen dubium due to fragmentary nature of the remains | Hypothetical restoration of the skeleton with the holotype material in white |
| Breviceratops kozlowskii | ZPAL MgD-I/117 | Polish Academy of Sciences | Early Maastrichtian | Barun Goyot Formation, Mongolia | Skull and partial postcrania | Was originally Protoceratops kozlowskii, may represent a juvenile Bagaceratops or Protoceratops | Digital reconstruction of the holotype in situ |
| Centrosaurus apertus | NMC 971 | Canadian Museum of Nature | Campanian | Dinosaur Park Formation, Alberta | Mostly complete skull | Originally Monoclonius dawsoni, but later referred to its own genus, type species of the subfamily "Centrosaurinae" and the tribe "Centrosaurini" | Illustration of the holotype |
| Cerasinops hodgskissi | MOR 300 | Museum of the Rockies | Campanian | Two Medicine Formation, Montana | Mostly complete skeleton | | The holotype with missing elements filled in |
| Ceratops montanus | USNM 2411 | Smithsonian Institution | Campanian | Upper Judith River Formation, Montana | Lacrimal horns and other skull elements | Nomen dubium, has been tentatively referred to Avaceratops, but is probably undiagnostic, type species of the suborder "Ceratopsia" and the family "Ceratopsidae" | Illustration of the holotype material |
| Chaoyangsaurus youngi | IGCAGS V371 | Chinese Academy of Geological Science | Late Tithonian | Tuchengzi Formation, Manchuria | Partial skull, vertebrae, and forelimb elements | Type species of the family "Chaoyangsauridae" | Diagram of the holotype material |
| Chasmosaurus belli | NMC 491 | Canadian Museum of Nature | Middle Campanian | Lower Dinosaur Park Formation, Alberta | Parietal bone | Type species of Chasmosaurus, originally named a species of the dubious genus Monoclonius, type species of the subfamily "Chasmosaurinae" | |
| Chasmosaurus brevirostris | ROM 839 | Royal Ontario Museum | Campanian | Dinosaur Park Formation, Alberta | Nasal and other skull elements without the frill | Generally considered synonymous with C. belli | |
| Chasmosaurus canadensis | USNM V6061 | Smithsonian Institution | Campanian | Judith River Formation, Montana | Partial dentary | Originally Monoclonius canadensis, was renamed Eoceratops canadensis, now considered Chasmosaurus sp. | |
| Chasmosaurus kaiseni | AMNH 5401 | American Museum of Natural History | Late Campanian | Dinosaur Park Formation, Alberta | Mostly complete skull | May belong to the dubious genus Mojoceratops or be synonymous with C. russelli | The holotype skull on display in New York City |
| Chasmosaurus russelli | NMC 8800 | Canadian Museum of Nature | Late Campanian | Upper Dinosaur Park Formation, Alberta | Parietal and other frill elements | Has been suggested to be synonymous with C. belli | |
| Coahuilaceratops magnacuerna | CPC 276 | Colección Paleontológica de Coahuila | Late Campanian | Cerro del Pueblo Formation, Mexico | Mostly complete limbs, several vertebrae, and skull elements | | Digital reconstruction of the holotype material |
| Colepiocephale lambei | GSC 8818 | Geological Survey of Canada | Early Campanian | Foremost Formation, Alberta | Frontoparietal dome | Originally Stegoceras lambei, but was later given its own genus | The holotype skull from multiple views |
| Coronosaurus brinkmani | TMP 2002.68.1 | Royal Tyrrell Museum | Campanian | Oldman Formation, Alberta | Frill and other skull elements | Originally Centrosaurus brinkmani, later given its own genus | The holotype on display in Alberta |
| Craspedodon lonzeensis | IRSNB 390 | Museum of Natural Sciences in Brussels | Santonian | Glauconie de Lonzée Formation, Belgium | Three isolated teeth | Most recently considered a ceratopsian, but may be an ornithopod | Holotype teeth |
| Crittendenceratops krzyzanowskii | NMMNH P-34906 | New Mexico Museum of Natural History | Late Campanian | Fort Crittenden Formation, Arizona | Parietal and squamosal skull elements | | |
| Diabloceratops eatoni | UMNH VP 16699 | Natural History Museum of Utah | Early Campanian | Wahweap Formation, Utah | Partial skull and lower jaw | | The skull, minus the lower jaw, in storage in Utah |
| Dracorex hogwartsia | TCMI 2004.17.1 | The Children's Museum of Indianapolis | Late Maastrichtian | Hell Creek Formation | Mostly complete skull and several vertebrae | May be a nomen dubium, this genus has been suggested to be the juvenile form of Pachycephalosaurus wyomingensis | The holotype skull mounted |
| Einiosaurus parvicursoris | MOR 456-8-9-6-1 | Museum of the Rockies | Late Campanian | Upper Two Medicine Formation, Montana | Nasal, supraorbital, and parietal elements of the skull | | Holotype skull (A$_1$) |
| Eotriceratops xerinsularis | RTMP 2002.57.5 | Royal Tyrrell Museum | Middle Maastrichtian | Upper Horseshoe Canyon Formation, Alberta | Multiple vertebrae, ribs, and parts of the skull | Some researchers have referred this to the genus Triceratops | |
| Ferrisaurus sustutensis | RBCM P900 | Royal British Columbia Museum | Late Maastrichtian | Tango Creek Formation, British Columbia | Front limb, hind limb, and shoulder elements | Specimen is nicknamed "Buster" | Diagram of the holotype material |
| Foraminacephale brevis | CMN 1423 | Canadian Museum of Nature | Campanian | Dinosaur Park Formation, Alberta | Frontoparietal dome | Was originally considered to be Stegoceras brevis, but was recently given its own genus | The holotype skull from multiple views |
| Furcatoceratops elucidans | NSM PV 24660 | National Museum of Nature and Science | Campanian | Judith River Formation, Montana | A mostly complete skeleton with skull fragments and some limb elements missing | | The holotype on display in Tokyo |
| Goyocephale lattimorei | GI SPS 100/1201 | Mongolian Academy of Sciences | Early Maastrichtian | Nemegt Formation, Mongolia | Complete skull, numerous caudal vertebrae, partial hip, and hindlimb elements | | Diagram of the holotype material |
| Graciliceratops mongoliensis | ZPAL MgD-I/156 | Polish Academy of Science | Uncertain (Albian to Santonian?) | Bayan Shireh Formation, Mongolia | Partial skull, mostly complete limbs, numerous vertebrae | Was originally named Microceratops mongoliensis | Diagram of the holotype material |
| Gravitholus albertae | TMP 1972.027.0001 | Royal Tyrrell Museum | Late Campanian | Dinosaur Park Formation, Alberta | Frontoparietal dome | | The holotype from above with arrows indicating supposed pathologies |
| Gremlin slobodorum | TMP 2011.053.0027 | Royal Tyrrell Museum | Middle Campanian | Oldman Formation, Alberta | A partial frontal bone | | |
| Gryphoceratops morrisoni | ROM 56635 | Royal Ontario Museum | Late Santonian to Early Campanian | Milk River Formation, Alberta | Partial dentary | | |
| Hanssuesia sternbergi | NMC 8817 | Canadian Museum of Nature | Middle Campanian | Dinosaur Park Formation, Alberta | Frontoparietal dome | Was erroneously assigned to the genusTroodon before being reassigned to Stegoceras, and finally being given its own genus, though some still consider it synonymous with the latter | |
| Helioceratops brachygnathus | JLUM L0204-Y-3 | Jilin Provincial Museum | Albian | Quantou Formation, Manchuria | Dentary | Paratype specimen includes a partial maxilla of the same scale as the holotype, but it could not be proven that it belongs to the same individual as the holotype | |
| Homalocephale calathoceros | MPC-D 100/1201 | Mongolian Natural History Museum | Early Maastrichtian | Nemegt Formation, Mongolia | Partial skull, mostly complete back legs, and numerous vertebrae | Has been suggested to be a juvenile specimen of Prenocephale, but this is largely rejected | The mounted holotype with missing elements |
| Hongshanosaurus houi | IVPP V12704 | Hong Kong Science Museum | Aptian | Yixian Formation, Liaoning | Several mostly complete skeletons | Nomen dubium, the specimens were renamed Psittacosaurus houi, but are now regarded as a synonym of P. lujiatunensis | The holotype skeletons in situ in Hong Kong |
| Hualianceratops wucaiwanensis | IVPP V18641 | Institute of Vertebrate Paleontology and Paleoanthropology | Early Oxfordian | Upper Shishugou Formation, Xinjiang | Partial postcranial skeleton with skull fragments | | Reconstruction with missing skull elements |
| Ischioceratops zhuchengensis | ZCDM V0O016 | Zhucheng Dinosaur Museum | Late Campanian or Early Maastrichtian | Xingezhuang Formation, Wangshi Group, Shandong | Partial legs, hip, and caudal vertebrae | | A photo and digital model of the holotype |
| Judiceratops tigris | YPM VPPU 022404 | Yale Peabody Museum | Middle Campanian | Judith River Formation, Montana | Horn, frill, and other skull fragments | | Parietal fragment of the holotype from multiple views |
| Koreaceratops hwaseongensis | KIGAM VP 200801 | Korean University of Science and Technology | Albian | Shiwa Formation, South Korea | Mostly complete tail and hind limb elements | | Skeletal reconstruction with the holotype elements on top |
| Kosmoceratops richardsoni | UMNH VP 17000 | Natural History Museum of Utah | Middle to Late Campanian | Kaiparowits Formation, Utah | Mostly complete skull, numerous ribs, vertebrae, and a partial hip | | The holotype skull from multiple views |
| Kulceratops kulensis | CCMGE 495/12457 | Chernyshev Central Geologic Exploration Museum | Late Albian | Khodzhakul Formation, Uzbekistan | Mostly complete maxilla | | |
| Leptoceratops gracilis | AMNH 5205 | American Museum of Natural History | Maastrichtian | Scollard Formation, Saskatchewan | Partial skeleton | Type species of the family "Leptoceratopsidae" | Forelimb of the holotype specimen |
| Liaoceratops yanzigouensis | IVPP V12738 | Institute of Vertebrate Paleontology and Paleoanthropology | Barremian | Yixian Formation, Liaoning | Mostly complete skull | | Diagram of the holotype material |
| Lokiceratops rangiformis | EMK 0012 | Museum of Evolution | Campanian | Judith River Formation, Montana | Mostly complete skull, shoulder, hip bones, and several vertebrae | | A skeletal reconstruction with the holotype material in orange |
| Machairocerastops cronusi | UMNH VP 20550 | Natural History Museum of Utah | Early Campanian | Wahweap Formation | Partial skull | | Diagram of the holotype material |
| Magnirostris dodsoni | IVPP V12513 | Institute of Vertebrate Paleontology and Paleoanthropology | Middle to Late Campanian | Bayan Mandahu Formation, Inner Mongolia | Partial skull with dentary | Now considered to be a junior synonym of Bagaceratops | The snout of the holotype |
| Medusaceratops lokii | WDC DJR 001 | Wyoming Dinosaur Center | Late Campanian | Upper Judith River Formation, Montana | Parietal frill | | Mounted cast of the holotype with the missing elements filled in |
| Menefeeceratops sealeyi | NMMNH P-25052 | New Mexico Museum of Natural History | Early Campanian | Menefee Formation, New Mexico | fragmentary skull, dentary, fragmentary vertebrae, ribs, limb elements, and a partial hip | | |
| Mercuriceratops gemini | ROM 64222 | Royal Ontario Museum | Middle Campanian | Judith River Formation, Montana | Squamosal bones | | |
| Micropachycephalosaurus hongtuyanensis | IVPP V5542 | Institute of Vertebrate Paleontology and Paleoanthropology | Late Campanian or Early Maastrichtian | Jiangjunding Formation, Shandong | Partial skull including dentary with fragmentary vertebrae, chevrons, and limb elements | | The illium associated with the holotype |
| Mojoceratops perifania | TMP 1983.25.1 | American Museum of Natural History | Late Campanian | Dinosaur Park Formation, Alberta | Mostly complete skull | May be synonymous with Chasmosaurus russelli or belong to its own species, C. kasenai (see above) | |
| Monoclonius crassus | AMNH 3998 | American Museum of Natural History | Campanian | Judith River Formation, Montana | Mostly complete parietal frill | Type species of Monoclonius, probably a nomen dubium and generally considered a junior synonym of Centrosaurus apertus | Illustration of the holotype |
| Monoclonius cutleri | AMNH 5427 | American Museum of Natural History | Campanian | Oldman Formation, Alberta | Partial skeleton | Nomen dubium and junior synonym of Centrosaurus apertus | |
| Monoclonius dawsoni | NMC 1173 | Canadian Museum of Nature | Campanian | Dinosaur Park Formation, Alberta | Partial skull and scapula | Nomen dubium and junior synonym of Centrosaurus apertus | |
| Monoclonius fissus | AMNH 3988 | American Museum of Natural History | Campanian | Dinosaur Park Formation, Alberta | Skull | Nomen dubium and junior synonym of Centrosaurus apertus | |
| Monoclonius flexus | AMNH 5239 | American Museum of Natural History | Campanian | Dinosaur Park Formation, Alberta | Mostly complete skull | Nomen dubium and junior synonym of Centrosaurus apertus | The holotype on display in New York City |
| Monoclonius longirostris | NMC 8795 | Canadian Museum of Nature | Late Campanian | Dinosaur Park Formation, Alberta | Skull | Nomen dubium and junior synonym of Centrosaurus apertus | |
| Monoclonius lowei | CMN 8790 | Canadian Museum of Nature | Campanian | Upper Dinosaur Park Formation, Alberta | Skull without dentary | Nomen dubium, but has not been referred to another genus or species | The holotype from multiple views |
| Monoclonius nasicornus | AMNH 5351 | American Museum of Natural History | Campanian | Dinosaur Park Formation, Alberta | Partial skeleton | Nomen dubium, has also been referred to the genus Centrosaurus, but is generally considered to be a synonym of Styracosaurus albertensis | |
| Monoclonius recurvicornis | AMNH 3999 | American Museum of Natural History | Campanian | Dinosaur Park Formation, Alberta | Partial skull elements | Nomen dubium, but has not been referred to another genus or species | An illustration of the holotype |
| Monoclonius sphenocerus | AMNH 3989 | American Museum of Natural History | Campanian | Dinosaur Park Formation, Alberta | Nasal horn and other skull fragments | Nomen dubium, but has not been referred to another genus or species | The holotype of M. sphenocerus labeled with a 2 |
| Montanoceratops cerorhynchus | AMNH 5464 | American Museum of Natural History | Easly Maastrichtian | Horseshoe Canyon Formation, Alberta | Mostly complete skull, vertebra, and hind foot with partial rib and limb elements | Originally considered a new species of Leptoceratops, but later given its own genus | Mounted skeleton based on the holotype material |
| Mosaiceratops azumai | ZMNH M8856 | Zhejiang Museum of Natural History | Uncertain (Turonian to Campanian?) | Xiaguan Formation, Henan | Mostly complete pelvis and legs with partial ribs, skull, and arm elements | | The holotype in situ along with a digital reconstruction |
| Nasutoceratops titusi | UMNH VP 16800 | Natural History Museum of Utah | Late Campanian | Kaiparowits Formation, Utah | Mostly complete skull, shoulders, and forelimbs with fragmentary vertebrae | Type species of the tribe "Nasutoceratopsini" | The holotype material from multiple views with skull bones labeled |
| Navajoceratops sullivani | SMP VP-1500 | State Museum of Pennsylvania | Late Campanian | Kirtland Formation, New Mexico | Parietal bones of the frill | | The holotype parietal bones |
| Nedoceratops hatcheri | USNM 2412 | Smithsonian Institution | Late Maastrichtian | Lance Formation, Wyoming | Complete skull without dentary | Was originally named Diceratops before it was discovered that this name was taken by a genus of wasp and was later renamed Diceratus before eventually being named Nedoceratops in 2008, might belong to Triceratops hatcheri or may simply be a specimen of Triceratops with unusual morphology | The holotype on display in Washington D.C. |
| Notoceratops bonarellii | Not catalogued | N/A, holotype has been lost | Maastrichtian | Lago Colhué Huapí Formation, Patagonia | Partial dentary | Nomen dubium, no other ceratopsian material is known from South America and the fragmentary nature was not studied enough to properly diagnose according to modern standards | An illustration of the holotype |
| Ojoceratops fowleri | SMP VP-1865 | State Museum of Pennsylvania | Maastrichtian | Ojo Alamo Formation, New Mexico | Squamosal skull bone | Has been suggested to be a synonym of Triceratops or possibly Eotriceratops | A reconstruction of the holotype with other referred material |
| Ornatotholus browni | AMNH 5450 | American Museum of Natural History | Campanian | Dinosaur Park Formation, Alberta | Frontoparietal dome | Nomen dubium, multiple studies have indicated that the holotype is probably a juvenile of the species Stegoceras validum | The holotype shown from multiple views |
| Pachycephalosaurus grangeri | AMNH 1696 | American Museum of Natural History | Maastrichtian | Lance Formation, Wyoming | Skull without dentary | Now considered a junior synonym of Pachycephalosaurus wyomingensis | The skull on display in New York City |
| Pachycephalosaurus reinheimeri | DMNH 469 | Denver Museum of Nature and Science | Maastrichtian | Lance Formation, Wyoming | Frontoparietal dome | Now considered a junior synonym of Pachycephalosaurus wyomingensis | The holotype shown from multiple views |
| Pachycephalosaurus wyomingensis | USNM 12031 | Smithsonian Institution | Maastrichtian | Lance Formation, Wyoming | Skull | Type species of Pachycephalosaurus, originally classified under the genus Troodon because of the similarity of its teeth to troodontid teeth, type species of the suborder "Pachycephalosauria", the family "Pachycephalosauridae", the subfamily "Pachycephalosaurinae", and the tribe "Pachycephalosaurini" | |
| Pachyrhinosaurus canadensis | NMC 8867 | Canadian Museum of Nature | Early Maastrichtian | Horseshoe Canyon Formation, Alberta | Partial skull | Type species of Pachyrhinosaurus and of the tribe "Pachyrhinosaurini" | |
| Pachyrhinosaurus lakustai | TMP 1986.55.258 | Royal Tyrrell Museum | Campanian | Wapiti Formation, Alberta | Skull | | The holotype skull on display with missing elements reconstructed with plaster |
| Pachyrhinosaurus perotorum | DMNH21200 | Denver Museum of Natural History | Early or Middle Maastrichtian | Prince Creek Formation, Alaska | Partial skull | | The holotype shown from multiple views |
| Pentaceratops aquilonius | CMN 9813 | Canadian Museum of Nature | Campanian | Dinosaur Park Formation, Alberta | Fragmentary skull elements | May be synonymous with Vagaceratops, Chasmosaurus, or Spiclypeus, material has been argued to be undiagnostic | The holotype material shown with multiple interpretations of its nature |
| Pentaceratops fenestratus | PMU.R200 | Uppsala University | Middle or Late Campanian | Kirtland Formation, New Mexico | Partial skull and relatively complete postcrania | Now considered a nomen dubium because the autapomorphy used to diagnose the new species was considered to be an injury or pathology | Illustration of the holotype skull in lateral view |
| Pentaceratops sternbergii | AMNH 6325 | American Museum of Natural History | Late Campanian | Fruitland Formation, New Mexico | Mostly complete skull | Type species of Pentaceratops | A photo of the holotype in lateral view |
| Platytholus clemensi | MOR 2915 | Museum of the Rockies | Maastrichtian | Hell Creek Formation, Montana | Partial skull | | |
| Polyonax mortuarius | AMNH FR 3950 | American Museum of Natural History | Uncertain | Colorado, locality not listed | Horn fragments and vertebrae | Nomen dubium, material too fragmentary to refer to a particular genus or species | |
| Prenocephale prenes | ZPAL MgD-I/104 | Polish Academy of Sciences | Maastrichtian | Nemegt Formation, Mongolia | Skull without a dentary | | Holotype skull in lateral view |
| Prenoceratops pieganensis | TCM 2003.1.1 | The Children's Museum of Indianapolis | Campanian | Two Medicine Formation | Articulated jaw bones | Specimen is nicknamed "Frannie" | A mounted cast composite modeled after the holotype and other associated specimens |
| Protoceratops andrewsi | AMNH 6251 | American Museum of Natural History | Campanian | Djadochta Formation, Mongolia | Rostrum | Type species of Protoceratops and of the family "Protoceratopsidae" | The holotype material with a ruler for scale |
| Protoceratops hellenikorhinus | IMM 95BM1/1 | Inner Mongolia Museum | Late Campanian | Bayan Mandahu Formation, Inner Mongolia | Complete skull | | The holotype on display in Hohhot |
| Psittacosaurus amitabha | IGM 100/1132 | Mongolian Academy of Sciences | Barremian | Andakhuduk Formation, Mongolia | Mostly complete skull | | |
| Psittacosaurus gobiensis | LH PV2 | Long Hao Institute of Geology and Paleontology | Late Barremian or Albian | Bayin-Gobi Formation, Inner Mongolia | Mostly complete skeleton including gastroliths | | |
| Psittacosaurus guyangensis | CAGS-IG V35 | Chinese Academy of Geological Sciences | Barremian to Aptian | Guyang Formation, Inner Mongolia | Anterior of the skull | Nomen dubium and junior synonym of P. mongoliensis | |
| Psittacosaurus lujiatunensis | ZMNH M8137 | Zhejiang Museum of Natural History | Aptian | Yixian Formation, Liaoning | Skull including dentary | | Cast of the holotype in Brussels |
| Psittacosaurus major | LH PV1 | Long Hao Institute of Geology and Paleontology | Late Barremian or Early Aptian | Yixian Formation | Mostly complete skeleton with skull | | The holotype, not including the post-cranial elements, shown from multiple views |
| Psittacosaurus mazongshanensis | IVPP V12165 | Institute of Vertebrate Paleontology and Paleoanthropology | Barremian | Xinminbao Group, Gansu | Partial lower jaw and maxilla | Nomen dubium, too fragmentary to refer to any specific species | |
| Psittacosaurus meileyingensis | IVPP V7705 | Institute of Vertebrate Paleontology and Paleoanthropology | Albian | Jiufotang Formation, Liaoning | Mostly complete skull without jugals | | |
| Psittacosaurus mongoliensis | AMNH 6254 | American Museum of Natural History | Uncertain (Aptian or Albian?) | Khukhtek Formation, Mongolia | Nearly complete skull and fully articulated skeleton | Type species of Psittacosaurus and of the monogeneric family "Psittacosauridae" | The holotype in situ on display in New York City |
| Psittacosaurus neimongoliensis | IVPP 12–0888-2 | Institute of Vertebrate Paleontology and Paleoanthropology | Aptian to Albian | Ejinhoro Formation, Inner Mongolia | Articulated skeleton with skull | | |
| Psittacosaurus ordosensis | IVPP 07–08888-1 | Institute of Vertebrate Paleontology and Paleoanthropology | Aptian to Albian | Ejinhoro Formation, Inner Mongolia | Half of a skull and a partial hind limb | Possibly a nomen dubium, may be a junior synonym of P. sinensis, but further material is awaiting description | |
| Psittacosaurus osborni | IVPP V41039 | Institute of Vertebrate Paleontology and Paleoanthropology | Uncertain (Aptian or Albian?) | Not listed, Guyang County | Partial skull | Nomen dubium and junior synonym of P. mongoliensis | |
| Psittacosaurus sattayaraki | TF 2449a | Phu Wiang Dinosaur Museum | Albian | Khot Kruat Formation, Thailand | Partial dentary | Nomen dubium, may not be diagnostic enough to refer to a particular genus, but some authors regard it as valid | |
| Psittacosaurus sibiricus | PM TGU 16/4-20 | Tomsk State University | Uncertain (younger than Albian) | Ilek Formation, Kemerovo | Skull with articulated skeleton | | The holotype on a temporary display in Moscow |
| Psittacosaurus sinensis | IVPP V738 | Institute of Vertebrate Paleontology and Paleoanthropology | Barremian to Albian | Qingshan Group, Shandong | Mostly complete skull and articulated skeleton | | |
| Psittacosaurus tingi | IVPP V31040 | Institute of Vertebrate Paleontology and Paleoanthropology | Uncertain (Aptian or Albian?) | Not listed, Guyang County | Fragmentary skull elements | Nomen dubium, the holotype is known to be a juvenile and has been considered a junior synonym of P. osborni and P. mongoliensis | |
| Psittacosaurus xinjiangensis | IVPP V7698 | Institute of Vertebrate Paleontology and Paleoanthropology | Aptian | Lianmuqin Formation, Xinjiang | Partial skull and articulated skeleton lacking some limb and tail elements | | |
| Psittacosaurus youngi | BNHM BPV149 | Museum of Vertebrate Zoology | Barremian to Albian | Doushan Formation, Qingshan Group, Shandong | Complete skull with partial hip, vertebrae, and limb elements | Nomen dubium, generally considered a junior synonym of P. sinensis | The holotype on display in situ in Zhengzhou |
| Regaliceratops peterhewsi | TMP 2005.055.0001 | Royal Tyrrell Museum | Early Maastrichtian | St. Mary River Formation, Alberta | Mostly complete skull | Specimen is nicknamed "Hellboy" | The holotype on display with missing elements filled in |
| Sasayamagnomus saegusai | MNHAH D1-060516 | Museum of Nature and Human Activities | Early Albian | Ohyamashimo Formation, Japan | Partial skull and lower jaw | Several specimens were referred in the description, but these were not included in the holotype | |
| Serendipaceratops arthurcclarkei | NMV P186385 | Melbourne Museum | Early Aptian | Wonthaggi Formation, Victoria | Ulna | Considered a nomen dubium, remains are so fragmentary that some believe it is not possible to diagnose them as a ceratopsian, some have referred the holotype to ankylosauria | |
| Sierraceratops turneri | NMMNH P-76870 | New Mexico Museum of Natural History | Late Campanian or Early Maastrichtian | Hall Lake Formation, New Mexico | Mostly complete skull and forelimb with a few vertebrae | | A vertebra from the holotype |
| Sinocephale bexelli | Not catalogued and now lost | Institute of Vertebrate Paleontology and Paleoanthropology was the holotype's last recorded location | Turonian, presumably | Uncertain, probably the Ulansuhai Formation, Inner Mongolia | Partial skull | Originally Troodon bexelli before being moved to the genus Stegoceras, specimens AMNH 2073 and PMU 23186 are plaster casts of the original holotype that were made and were used to diagnose it as a new genus | |
| Sinoceratops zhuchengensis | ZCDM V0010 | Zhucheng Dinosaur Museum | Late Campanian or Early Maastrichtian | Xingezhuang Formation, Shandong | Partial skull with intact braincase | | Digital reconstruction of the holotype skull viewed from the side |
| Sphaerotholus buchholtzae | TMP 87.113.3 | Royal Tyrrell Museum | Maastrichtian | Hell Creek Formation, Montana | Incomplete skull | Once considered a junior synonym of S. edmontonensis, now generally considered its own species | |
| Sphaerotholus edmontonensis | GSC 8830 | Canadian Museum of Nature | | | Frotoparietal dome | Originally assigned to Troodon before being renamed as a species of Prenocephale and later Stegoceras before being referred to Sphaerotholus | |
| Sphaerotholus goodwini | NMMNH P-27403 | New Mexico Museum of Natural History | Campanian | Kirtland Formation, New Mexico | Incomplete skull | Type species of Sphaerotholus | |
| Sphaerotholus lyonsi | TMP 2002.12.63 | Royal Tyrell Museum | Campanian | Dinosaur Park Formation, Alberta | One of the squamosals | | |
| Sphaerotholus triregnum | ROM 53583 | Royal Ontario Museum | Maastrichtian | Hell Creek Formation, Montana | Partial frontoparietal dome | | |
| Spiclypeus shipporum | CMN 57081 | Canadian Museum of Nature | Late Campanian | Judith River Formation, Montana | Partial skull with a few vertebrae, ribs, and limb bones | | Holotype with frill elements labeled |
| Sphaerotholus triregnum | ROM 53583 | Royal Ontario Museum | Late Maastrichtian | Hell Creek Formation, Montana | One of the squamosals | | |
| Spinops sternbergorum | NHMUK R16307 | Natural History Museum, London | Campanian | Oldman Formation or Dinosaur Park Formation, Alberta | Partial parietal | | The bones of the holotype labeled and shown in multiple views |
| Stegoceras novomexicanum | NMMNH P-33983 | New Mexico Museum of Natural History | Campanian | Fruitland Formation, New Mexico | Frontoparietal dome | May be a nomen dubium, holotype may be a juvenile and has been referred variously to Stegoceras sp., S. validum, and Sphaerotholus goodwini | |
| Stegoceras validum | NMC 515 | Canadian Museum of Nature | Campanian | Dinosaur Park Formation, Alberta | Frontoparietal dome | Type species of Stegoceras, there were initially two "syntypes", but one was selected as the "lectotype" or "new holotype" | The holotype shown from multiple views |
| Stellasaurus ancellae | MOR 492 | Museum of the Rockies | Late Campanian | Two Medicine Formation, Montana | Parietal frill with epiossifications, nasal horn, and other skull elements | | Parietal portion of the holotype |
| Stenopelix valdensis | GZG 741/2 | University of Göttingen | Late Berriasian | Obernkirchen Sandstein Formation, Germany | Mostly complete ribs, vertebrae, hips, tail, and limbs with no skull | | Plaster casts of the holotype alongside digital reconstructions |
| Stenotholus kohleri | MPM 7111 | University of California Museum of Paleontology | Maastrichtian | Hell Creek Formation, Montana | Partial skull with an intact braincase | Nomen dubium and probably a junior synonym of Pachycephalosaurus wyomingensis or Stygimoloch spinifer | |
| Stygimoloch spinifer | UCMP 110433 | University of California Museum of Paleontology | Maastrichtian | Hell Creek Formation, Montana | Skull | Validity disputed, has been considered Pachycephalosaurus spinifer or a juvenile form of P. wyomingensis | Skull elements of the holotype laid out individually |
| Styracosaurus albertensis | NMC 344 | Canadian Museum of Nature | Campanian | Dinosaur Park Formation, Alberta | Complete skull | Type species of Styracosaurus | The holotype on display mounted on a restored skeleton |
| Styracosaurus ovatus | USNM 11869 | Smithsonian Institution | Campanian | Two Medicine Formation, Alberta | Partial frill with epiparietals | Originally assigned to Styracosaurus, this specimen was later given its own genus, Rubeosaurus, now broadly considered to either be S. ovatus or a junior synonym of S. albertensis | The holotype frill with elements labeled |
| Styracosaurus parksi | AMNH 5372 | American Museum of Natural History | Campanian | Dinosaur Park Formation, Alberta | Mostly complete skeleton | Now considered a junior synonym of S. albertensis | The holotype in a display at the American Museum of Natural History |
| Tatankaceratops sacrinsonorum | BHI 6226 | Black Hills Institute | Late Maastrichtian | Hell Creek Formation, South Dakota | Partial skull | Nomen dubium, generally considered to be a juvenile or aberrant specimen of Triceratops | Diagram of the holotype material |
| Terminocavus sealeyi | NMMNH P-27468 | New Mexico Museum of Natural History | Late Campanian | Kirtland Formation, New Mexico | Parietal with other skull elements and vertebral fragments | | The holotype shown from the front and behind |
| Texacephale langstoni | LSUMNS 20010 | Louisiana State University Museum of Natural Science | Late Campanian | Aguja Formation, Texas | Frontoparietal bone | | Skull dome of the holotype shown in multiple views |
| Titanoceratops ouranos | OMNH 10165 | Sam Noble Oklahoma Museum of Natural History | Late Campanian | Upper Fruitland Formation or Lower Kirtland Formation, New Mexico | Partial skull, numerous limb bones, fragmentary ribs and vertebrae | | Diagram of the holotype material |
| Torosaurus gladius | YPM 1831 | Yale Peabody Museum | Maastrichtian | Lance Formation, Wyoming | Skull | Nomen dubium, found to be a junior synonym of T. latus | Holotype (top) compared to a putative Torosaurus subadult |
| Torosaurus latus | YPM 1830 | Yale Peabody Museum | Maastrichtian | Lance Formation, Wyoming | Mostly complete skull | Type species of Torosaurus, has been argued to be a junior synonym of Triceratops, but this has not been widely accepted | Illustration of the holotype by Othniel Charles Marsh |
| Torosaurus utahensis | USNM 15583 | Smithsonian Institution | Maastrichtian | North Horn Formation, Utah | Parietal and quadrate fragments | | |
| Triceratops albertensis | NMC 8862 | Canadian Museum of Nature | Maastrichtian | Scollard Formation, Alberta | Partial skull | Nomen dubium, junior synonym of T. horridus | |
| Triceratops alticornis | USNM V4739 | Smithsonian Institution | Maastrichtian | Denver Formation, Colorado | Horns and brow ridge | Nomen dubium, originally misidentified as a species of Bison before being referred to Triceratops, now considered Triceratops sp. | An illustration of the holotype |
| Triceratops brevicornus | YPM 1834 | Yale Peabody Museum | Maastrichtian | Lance Formation, Wyoming | Partial skull | Junior synonym of T. horridus | |
| Triceratops calicornis | USNM 4928 | Smithsonian Institution | Maastrichtian | Lance Formation, Wyoming | Skull and partial skeleton | Junior synonym of T. horridus | An illustration of the holotype |
| Triceratops elatus | USNM V1201 | Smithsonian Institution | Maastrichtian | Lance Formation, Wyoming | Partial skull | Junior synonym of T. horridus | An illustration of the holotype |
| Triceratops eurycephalus | MCZ 1102 | Museum of Comparative Zoology | Maastrichtian | Lance Formation, Wyoming | Partial skeleton | Junior synonym of T. horridus | |
| Triceratops flabellatus | YPM 1821 | Yale Peabody Museum | Maastrichtian | Lance Formation, Wyoming | Skull | Junior synonym of T. horridus | An illustration of the holotype skull from below, showing the palate |
| Triceratops galeus | USNM V2410 | Smithsonian Institution | Maastrichtian | Denver Formation, Colorado | Fragmentary parietal | Junior synonym of T. horridus | |
| Triceratops horridus | YPM 1820 | Yale Peabody Museum | Maastrichtian | Lance Formation, Wyoming | Mostly complete skull | Type species of Triceratops, official dinosaur of the state of Wyoming, originally named Ceratops horridus before being given its own genus, type species of the tribe "Triceratopsini" | An illustration of the holotype |
| Triceratops ingens | YPM 1828 | Yale Peabody Museum | Maastrichtian | Never formally published and described | Partial skull | Nomen dubium, it is not certain if this is T. horridus, T. prorsus, of T. sp. | |
| Triceratops maximus | AMNH 5040 | American Museum of Natural History | Maastrichtian | Hell Creek Formation, Montana | Eight vertebrae and a few rib fragments | Nomen dubium, material is not diagnostic enough to assign it to any particular genus | |
| Triceratops obtusus | USNM 4720 | Smithsonian Institution | Maastrichtian | Lance Formation, Wyoming | Partial skull | Nicknamed "Hatcher", junior synonym of T. horridus | Hatcher on display in Washington, D.C. |
| Triceratops prorsus | YPM 1822 | Yale Peabody Museum | Maastrichtian | Laramie Formation, Wyoming | Complete skull | The only other species of Triceratops, besides T. horridus that is universally considered to be valid | The holotype of T. prorsus (top) compared to a specimen nicknamed "Yoshi's Trike" |
| Triceratops serratus | YPM 1823 | Yale Peabody Museum | Maastrichtian | Laramie Formation, Colorado | Mostly complete skull | Junior synonym of T. horridus | Illustration of the holotype |
| Triceratops sulcatus | USNM V4286 | Smithsonian Institution | Maastrichtian | Lance Formation, Wyoming | Jaw fragment with partial horn core | Junior synonym of T. horridus | Illustration of the jaw portion of the holotype from multiple views |
| Turanoceratops tardabilis | CCMGE 251/12457 | Chernyshev Central Museum of Geological Exploration | Turonian | Bissekty Formation, Uzbekistan | Partial maxilla | | |
| Tylocephale gilmorei | ZPAL MgD-I/105 | Polish Academy of Sciences | Campanian | Barun Goyot Formation, Mongolia | Mostly complete skull | | Diagram of the holotype material |
| Tylosteus ornatus | ANSP 8568 | Academy of Natural Sciences of Drexel University | Maastrichtian | Lance Formation, Montana | Partial skull | Nomen dubium, was named before Pachycephalosaurus, and probably refers to the same animal, but the latter name was given priority | |
| Udanoceratops tchizhovi | PIN 3907/11 | Russian Academy of Sciences | Campanian | Djadochta Formation, Mongolia | Mostly complete skull and a few vertebrae | | Diagram of the holotype material |
| Ugrosaurus olsoni | UCMP 128561 | Museum of Vertebrate Zoology | Late Maastrichtian | Hell Creek Formation, Montana | Fragments of the premaxilla, dentary, and parietal bones | Nomen dubium, not diagnostic from Triceratops, which existed in the same time and place as U. olsoni | |
| Unescoceratops kopelhusae | TMP 95.12.6 | Royal Tyrrell Museum | Campanian | Dinosaur Park Formation, Alberta | Partial dentary | | |
| Utahceratops gettyi | UMNH VP 16784 | Utah Museum of Natural History | Campanian | Kaiparowits Formation, Utah | Disarticulated, mostly complete skull | | Labeled holotype elements with a reconstruction of a complete skull below |
| Vagaceratops irvinensis | CMN 41357 | Canadian Museum of Nature | Late Campanian | Dinosaur Park Formation, Alberta | Frill and mostly complete postcrania | Sometimes considered to belong to the genus Chasmosaurus as the species C. irvinensis | The holotype on display as it was found |
| Wannanosaurus yansiensis | IVPP V4447 | Institute of Vertebrate Paleontology and Paleoanthropology | Early or Middle Maastrichtian | Xiaoyan Formation, Anhui | Partial skull roof and lower jaw, femur, tibia, part of a rib, and other postcranial fragments | | Skull fragments of the holotype, with the postcranial elements omitted |
| Wendiceratops pinhornensis | TMP2011.051.0009 | Royal Tyrrell Museum | Campanian | Oldman Formation, Alberta | Parietal bone | | The holotype shown from multiple views with the epiparietals labeled |
| Xenoceratops foremostensis | CMN 53282 | Canadian Museum of Nature | Early Campanian | Foremost Formation, Alberta | Parietal bone | | |
| Xuanhuaceratops niei | IVPP 12722 | Institute of Vertebrate Paleontology and Paleoanthropology | Tithonian | Houcheng Formation, Hebei | Mostly complete skull, numerous vertebrae, partial hip, shoulder, and limb elements | | |
| Yamaceratops dorngobiensis | IGM 100/1315 | Mongolian Academy of Sciences | Santonian | Javkhlant Formation, Mongolia | Mostly complete skull | | Holotype shown from multiple views |
| Yinlong downsi | IVPP V14530 | Institute of Vertebrate Paleontology and Paleoanthropology | Oxfordian | Shishugou Formation, Xinjiang | Complete skeleton with skull | | |
| Zhuchengceratops inexpectus | ZCDM V0015 | Zhucheng Dinosaur Museum | Early Maastrichtian | Xingezhuang Formation, Shandong | Partial skull with a mostly complete skeleton | | The skull and jaw elements of the holotype |
| Zuniceratops christopheri | MSM P2101 | Arizona Museum of Natural History | Turonian | Moreno Hill Formation, New Mexico | Partial skull and limb elements | | |