List of the Mesozoic life of Colorado

This list of the Mesozoic life of Colorado contains the various prehistoric life-forms whose fossilized remains have been reported from within the US state of Colorado and are between 252.17 and 66 million years of age.

A

 * †Acanthichnus – tentative report
 * Acila
 * †Acila chicotana
 * Acmaea
 * †Acmaea genettae – type locality for species
 * †Adocus
 * †Albanerpeton
 * †Albanerpeton nexuosus
 * †Albertosaurus – tentative report
 * †Allantodiopsis
 * †Allantodiopsis erosa
 * †Allantodiopsis JC018 – informal
 * Allosaurus Revised.jpg †[[Allosaurus]] – type locality for genus
 * †Allosaurus fragilis – type locality for species
 * †Allosaurus lucasi – type locality for species
 * †Amblotherium – type locality for genus
 * †Amblotherium gracilis
 * Amia
 * †Amphicoelias – type locality for genus
 * †Amphicoelias altus – type locality for species
 * Goniopholis skull.JPG †[[Amphicotylus]]
 * †Amphicotylus lucasii – type locality for species
 * †Amplovalvata
 * †Amplovalvata scabrida
 * †Anaklinoceras
 * †Anaklinoceras minutum – type locality for species
 * †Anaklinoceras reflexum
 * †Anisoceras
 * †Anisoceras plicatilis
 * †Anisomyon
 * †Anisomyon centrale
 * †Anomia
 * †Anomia subquadrata
 * †Anomia tellinoides
 * Anomoepus cropped.png †[[Anomoepus]] – tentative report
 * †Apateodus
 * †Apatopus
 * †Apatosaurus – type locality for genus
 * †Apatosaurus ajax – type locality for species
 * †Apatosaurus laticollis – type locality for species. Junior synonym of A. louisae.
 * †Apatosaurus louisae
 * †Arcellites
 * †Arcellites disciformis
 * †Archaeolamna
 * †Archaeolamna kopingensis
 * †Arenicolites
 * Aspideretes
 * †Aspideretes vagans – type locality for species
 * †Aspideretoides
 * Astarte
 * †Atlantosaurus
 * †Atlantosaurus immanis – type locality for species
 * †Axonoceras
 * †Axonoceras compressum

B

 * †Baculites
 * †Baculites aquilaensis
 * †Baculites asper
 * †Baculites clinolobatus – type locality for species
 * †Baculites codyensis
 * †Baculites compressus
 * †Baculites cuneatus
 * †Baculites grandis
 * †Baculites haresi
 * †Baculites mclearni
 * †Baculites meeki – type locality for species
 * †Baculites reesidei
 * Barosaurus lentus1.jpg †[[Barosaurus]]
 * †Basilemys
 * †Basilemys sinuosa – or unidentified comparable form
 * †Behuninia
 * †Behuninia provoensis
 * †Bellifusus
 * †Bison
 * †Bison alticornis – type locality for species
 * †Borealosuchus
 * †Borealosuchus sternbergii
 * †Brachauchenius – or unidentified comparable form
 * †Brachiosaurus – type locality for genus
 * †Brachiosaurus altithorax – type locality for species
 * †Brachychampsa
 * †Brachychampsa montana
 * †Brachychirotherium
 * †Brachyphyllum
 * †Brachyphyllum rechtenii – type locality for species
 * Brontosaurus NT small.jpg †[[Brontosaurus]]
 * †Brontosaurus excelsus
 * †Brontosaurus yahnahpin

C

 * †Calycoceras
 * †Calycoceras canitaurinum
 * †Calycoceras naviculare
 * Camarasaurs1.jpg †[[Camarasaurus]] – type locality for genus
 * †Camarasaurus agilis – type locality for species
 * †Camarasaurus grandis
 * †Camarasaurus lewisi
 * †Camarasaurus supremus – type locality for species
 * †Camptosaurus – type locality for genus
 * †Camptosaurus dispar – type locality for species
 * Carcharias
 * †Carcharias amonensis
 * †Carcharias saskatchewanensis
 * †Carcharias tenuiplicatus
 * †Caririchnium
 * †Caririchnium leonardii – type locality for species
 * †Caririchnium leonaridii
 * †Cataceramus
 * †Cataceramus gladbeckensis
 * †Cedrobaena
 * †Cedrobaena brinkman
 * †Ceratodus – type locality for genus
 * †Ceratodus felchi – type locality for species
 * †Ceratodus guentheri – type locality for species
 * Ceratosaurus nasicornis DB.jpg †[[Ceratosaurus]] – type locality for genus
 * †Ceratosaurus nasicornis – type locality for species
 * Cerithiopsis
 * †Champsosaurus
 * Chara
 * †Chelonipus
 * †Chinlea
 * †Chinlea sorenseni
 * †Chinlestegophis – type locality for genus
 * †Chinlestegophis jenkinsi – type locality for species
 * †Chirotherium
 * †Chirotherium lulli
 * †Cimolichthys
 * †Cimolichthys nepaholica
 * †Cimolodon – or unidentified comparable form
 * Ptilodus.jpg †[[Cimolomys]]
 * †Cionichthys
 * †Cionichthys dunklei
 * †Cionodon – type locality for genus
 * †Cionodon arctatus – type locality for species
 * †Cirroceras
 * †Cirroceras conradi
 * †Cladoceramus
 * †Cladoceramus undulatoplicatus
 * †Clidastes
 * †Clioscaphites
 * †Clioscaphites choteauensis
 * †Clioscaphites saxitonianus
 * †Clioscaphites vermiformis
 * †Coahuilites
 * †Coahuilites sheltoni
 * †Cochlichnus
 * †Codellaster – type locality for genus
 * †Codellaster keepersae – type locality for species
 * †Coelophysis – tentative report
 * Coelurus.jpg †[[Coelurus]]
 * †Coelurus fragilis
 * †Compsemys
 * †Compsemys victa
 * †Coniasaurus
 * †Coniasaurus crassidens
 * Corbula
 * †Corydalites – type locality for genus
 * †Corydalites fecundum – type locality for species
 * Crassatella
 * †Crassatella franzeseii
 * †Cremnoceramus
 * †Cremnoceramus deformis
 * †Crenella
 * †Creonella
 * †Creonella triplicata
 * †Cretodus
 * †Cretodus semiplicatus
 * †Cretolamna
 * †Cretolamna appendiculata
 * †Cretomanta
 * †Cretomanta canadensis
 * Cretoxyrhina mantelli 21DB.jpg †[[Cretoxyrhina]]
 * †Cretoxyrhina mantelli
 * Cucullaea
 * †Cucullaea nebrascensis
 * Cuspidaria
 * †Cuspidaria ventricosa
 * †Czekanowskia
 * †Czekanowskia turneri – tentative report

D

 * †Diablophis
 * †Diablophis gilmorei – type locality for species
 * †Didymoceras
 * †Didymoceras aurarium – type locality for species
 * †Didymoceras cheyennense
 * †Didymoceras draconis
 * †Didymoceras stevensoni
 * †Dinehichnus
 * †Dinehichnus socialis
 * †Dinochelys
 * †Dinochelys whitei
 * Diplodocus scale.png (green) and D. hallorum (orange) with an anachronistic human to scale.]] †Diplodocus'' – type locality for genus
 * †Diplodocus lacustris – type locality for species
 * †Diplodocus longus – type locality for species
 * Diplodonta
 * †Diplodonta davisi
 * †Diplosaurus
 * †Diplosaurus felix – type locality for species
 * Discinisca
 * †Discoscaphites
 * †Discoscaphites conradi
 * †Docodon
 * †Docodon apoxys – type locality for species
 * †Dorsetisaurus
 * Dorsetochelys skull Dorset County Museum.JPG †[[Dorsetochelys]]
 * †Dorsetochelys buzzops – type locality for species
 * †Drepanocheilus
 * †Drepanocheilus evansi
 * †Drepanocheilus nebrascensis
 * †Drepanocheilus obesus
 * †Dryophyllum
 * †Dryophyllum tennesseensis
 * †Dryosaurus
 * †Dryosaurus altus

E

 * †Edmontonia
 * Edmontosaurus regalis.PNG with an anachronistic human to scale]] †Edmontosaurus''
 * †Edmontosaurus regalis – type locality for species
 * Eilenodon – type locality for genus
 * †Eilenodon robustus – type locality for species
 * †Elopopsis
 * †Enchodus
 * †Enchodus gladiolus – or unidentified comparable form
 * †Enchodus shumardi – or unidentified comparable form
 * †Entolium
 * †Eoacteon
 * †Eoacteon sublinearis
 * †Eomunidopsis
 * †Eomunidopsis cobbani – type locality for species
 * †Eosauropus
 * †Eosauropus cimarronensis
 * †Eosauropus cimmaronensis
 * Equisetopsida.jpg †[[Equisetum]]
 * †Equisetum burchardtii – or unidentified comparable form
 * †Etea
 * †Etea peasei
 * †Eubrontes
 * †Eubrontes giganteus
 * †Eucalycoceras
 * †Eucalycoceras pentagonum
 * †Euomphaloceras
 * †Euomphaloceras septemseriatum
 * †Eutrephoceras
 * †Eutrephoceras dekayi
 * †Eutretauranosuchus – type locality for genus
 * †Eutretauranosuchus delfsi – type locality for species
 * †Exiteloceras
 * †Exiteloceras jenneyi
 * †Exogyra
 * †Exogyra boveyensis – or unidentified related form

F

 * Fagesia spheroidalis.jpg †[[Fagesia]]
 * Ficus
 * †Ficus planicostata
 * †Forresteria
 * †Forresteria hobsoni – type locality for species
 * †Fruitachampsa – type locality for genus
 * †Fruitachampsa callisoni – type locality for species
 * †Fruitadens – type locality for genus
 * †Fruitadens haagarorum – type locality for species
 * †Fruitafossor – type locality for genus
 * †Fruitafossor windscheffeli – type locality for species

G

 * Galeamopus pabsti skull.jpg †[[Galeamopus]]
 * †Galeamopus pabsti
 * †Glirodon
 * †Glirodon grandis
 * †Glyptops
 * †Glyptops plicatulus – type locality for species
 * †Goniopholis
 * †Goniopholis felchi – type locality for species
 * †Grallator
 * †Grallator cursorius
 * †Grallator tenuis
 * †Gryphaeostrea
 * †Gwyneddichnium
 * †Gypsonictops
 * †Gyroides

H

 * Hallopus NT.jpg †[[Hallopus]]
 * †Hallopus victor – type locality for species
 * †Haplocanthosaurus – type locality for genus
 * †Haplocanthosaurus delfsi – type locality for species
 * †Haplocanthosaurus priscus – type locality for species
 * †Harduinia
 * †Harduinia stantoni
 * †Harduinia taylori
 * †Haresiceras
 * †Haresiceras placentiforme
 * †Helopanoplia
 * †Helopanoplia distincta – or unidentified comparable form
 * †Hemicalypterus
 * †Hermanophyton
 * [[File:Placenticeras costatum, Cretaceous, Pierre Shale Formation, Cheyenne River, Pennington County, South Dakota, USA - Houston Museum of Natural Science - DSC02011.JPG|thumb|upright=0.634|Fossilized shell of the Late Cretaceous ammonoid cephalopod Herrickiceras]] †[[Herrickiceras]]
 * †Herrickiceras costatus
 * †Holaster
 * †Holaster feralis – type locality for species
 * †Homolopsis
 * †Hoploscaphites
 * †Hoploscaphites birkelundae
 * †Hoploscaphites landesi
 * †Hoploscaphites macer
 * †Hoploscaphites nicolletii
 * †Hulettia – report made of unidentified related form or using admittedly obsolete nomenclature
 * †Hulettia hawesi – type locality for species
 * †Hypsirophus – type locality for genus
 * †Hypsirophus discurus – type locality for species

I

 * †Ichthyodectes
 * †Ignotornis – type locality for genus
 * †Ignotornis mcconnelli – type locality for species
 * Inoceramus steenstrup, world's largest fossil mollusk.jpg †[[Inoceramus]]
 * †Inoceramus altus
 * †Inoceramus altusiformis
 * †Inoceramus anomalus
 * †Inoceramus arnoldi
 * †Inoceramus balticus
 * †Inoceramus brancoiformis
 * †Inoceramus bueltenensis
 * †Inoceramus cordiformis
 * †Inoceramus crippsi – or unidentified related form
 * †Inoceramus deformis
 * †Inoceramus erectus
 * †Inoceramus flavus
 * †Inoceramus grandis
 * †Inoceramus longealatus
 * †Inoceramus muelleri - or unidentified loosely related form
 * †Inoceramus oblongus
 * †Inoceramus pictus
 * †Inoceramus prefragilis
 * †Inoceramus rutherfordi – or unidentified comparable form
 * †Inoceramus tenuistriatus – tentative report
 * †Ischyrhiza
 * †Ischyrhiza avonicola – or unidentified comparable form

J

 * Ammonite Jeletzkytes.jpg †[[Jeletzkytes]]
 * †Jeletzkytes brevis
 * †Jeletzkytes dorfi
 * †Jeletzkytes nodosus
 * †Jensensispermum
 * †Jensensispermum redmondii
 * Jupiteria
 * †Jupiteria scitula

K

 * †Kepodactylus – type locality for genus
 * †Kepodactylus insperatus – type locality for species

L

 * †Laosaurus – report made of unidentified related form or using admittedly obsolete nomenclature
 * Laternula
 * Lepisosteus – tentative report
 * †Lepisosteus occidentalis
 * †Leptalestes – tentative report
 * †Leptalestes cooki
 * Leptolepis NT.jpg †[[Leptolepis]] – or unidentified comparable form
 * †Lewyites
 * †Lewyites oronensis
 * Lima
 * †Lima janetae – type locality for species
 * †Lingula
 * †Lioestheria
 * †Lioestheria tendagurensis – or unidentified comparable form
 * †Lisserpeton
 * †Lisserpeton bairdi
 * †Lonchidion
 * †Lonchidion selachos
 * †Lucina
 * †Lyropecten

M

 * Macelognathus vagans.jpg †[[Macelognathus]]
 * †Macelognathus vagans
 * †Magadiceramus
 * †Magadiceramus complicatus
 * †Magadiceramus crenelatus
 * †Magadiceramus soukupi - or unidentified loosely related form
 * †Magadiceramus subquadratus
 * †Magnoavipes
 * †Magnoavipes caneeri – type locality for species
 * †Marmarthia – or unidentified comparable form
 * †Marmarthia pearsonii
 * †Marshosaurus – or unidentified comparable form
 * Meniscoessus skull.jpg †[[Meniscoessus]]
 * †Meniscoessus collomensis – type locality for species
 * †Meniscoessus conquistus
 * †Meniscoessus robustus – or unidentified comparable form
 * †Mesadactylus – type locality for genus
 * †Mesadactylus ornithosphyos – type locality for species
 * †Mesembrioxylon
 * †Mesembrioxylon carterii – type locality for species
 * †Mesodma
 * †Mesodma formosa – or unidentified comparable form
 * †Mesojassoides – type locality for genus
 * †Mesojassoides gigantea – type locality for species
 * †Mesolanistes
 * †Mesolanistes reesidei
 * †Metengonoceras
 * †Metengonoceras dumbli
 * †Metoicoceras
 * †Metoicoceras geslinianum
 * †Micrabacia
 * †Micrabacia radiata
 * †Micropycnodon
 * †Micropycnodon kansasensis
 * †Modiolus
 * †Modiolus kremmlingensis – type locality for species
 * †Modiolus meeki
 * †Moremanoceras
 * †Moremanoceras scotti
 * †Morosaurus
 * †Morosaurus laticollis – type locality for species
 * †Morrolepis
 * †Morrolepis schaefferi – type locality for species
 * †Myledaphus
 * †Myledaphus bipartitus
 * Mymoorapelta.jpg †[[Mymoorapelta]] – type locality for genus
 * †Mymoorapelta maysi – type locality for species
 * Myrica
 * †Myrica torreyi
 * †Mytiloides
 * †Mytiloides duplicostatus – or unidentified related form
 * †Mytiloides latus – or unidentified comparable form
 * †Mytiloides mytiloides
 * †Mytiloides opalensis
 * †Mytiloides stantoni – or unidentified comparable form
 * †Mytiloides submytiloides – or unidentified related form

N

 * †Nanosaurus – type locality for genus
 * †Nanosaurus agilis – type locality for species
 * †Nanosaurus rex
 * Natica crassa 01.JPG [[Natica]]
 * †Nemodon
 * †Nemodon adkinsi
 * †Nemodon harriesi – type locality for species
 * †Neocardioceras
 * †Neocardioceras densicostatum – type locality for species
 * †Neocardioceras juddii
 * †Neocardioceras laevigatum
 * †Neocardioceras minutum
 * †Neocardioceras uptonense
 * †Neocrioceras
 * †Neoptychites
 * †Neoptychites cephalotus
 * †Neurankylus
 * †Nigericeras
 * †Nigericeras scotti – type locality for species
 * †Nonactaeonina
 * †Nonactaeonina deflexa
 * †Nonactaeonina triticea
 * †Nortedelphys
 * †Nortedelphys jasoni
 * Nostoceras species cropped.jpg †[[Nostoceras]]
 * †Nostoceras approximans – or unidentified comparable form
 * †Nostoceras larimerense – type locality for species
 * †Nostoceras monotuberculatum
 * †Nostoceras obtusum – or unidentified comparable form
 * †Nostoceras splendidum – or unidentified comparable form
 * Nucula
 * †Nucula percrassa
 * Nuculana
 * †Nymphalucina
 * †Nymphalucina bourni – type locality for species
 * †Nymphalucina cleburni

O

 * †Octopodichnus
 * †Odaxosaurus
 * †Odaxosaurus piger
 * †Oligoptycha
 * †Oligoptycha concinna
 * †Opertochasma
 * †Opertochasma cuneatum
 * †Opisthias
 * †Opisthotriton
 * †Opisthotriton kayi
 * †Ornitholestes – tentative report
 * †Ornithomimipus
 * †Ornithomimipus angustus – or unidentified comparable form
 * Ornithomimus edmontonicus.jpg †[[Ornithomimus]] – type locality for genus
 * †Ornithomimus velox – type locality for species
 * Ostrea
 * †Ostrea beloiti
 * †Ostrea subradiata
 * †Othnielia – tentative report
 * †Othnielosaurus
 * †Othnielosaurus consors
 * †Oxybeloceras
 * †Oxybeloceras crassum
 * †Oxytoma

P

 * Pachycephalosaurus skull.JPG †[[Pachycephalosaurus]]
 * †Pachyrhizodus
 * †Pachyrhizodus minimus
 * †Palaeobalistum
 * †Palaeopteryx – type locality for genus
 * †Paleonelumbo
 * †Paleonelumbo macroloba
 * †Parabrontopodus – type locality for genus
 * †Parabrontopodus mcintoshi – type locality for species
 * †Parallelodon
 * †Paramacellodus
 * †Parapleurites
 * †Parapleurites morrisonensis – type locality for species
 * †Paressonodon – type locality for genus
 * †Paressonodon nelsoni – type locality for species
 * †Parikimys – type locality for genus
 * †Parikimys carpenteri – type locality for species
 * †Parviraptor
 * Pentaceratops BW.jpg †[[Pentaceratops]]
 * †Pentaceratops sternbergii
 * †Pentasauropus
 * †Petropteron – type locality for genus
 * †Petropteron mirandum – type locality for species
 * †Phelopteria
 * †Phelopteria linguaeformis
 * †Phelopteria ruppii – type locality for species
 * †Phlycticrioceras
 * †Phlycticrioceras trinodosus
 * †Pinna
 * †Placenticeras
 * †Placenticeras meeki
 * †Placenticeras placentum
 * †Placenticeras syrtale
 * †Plastomenus – tentative report
 * †Plastomenus insignis – type locality for species
 * †Plastomenus punctulatus – type locality for species
 * †Platanites
 * †Platanites marginata
 * [[File:Platyceramus platinus with Pseudoperna congesta, Gove County, Kansas, USA, Late Cretaceous - Royal Ontario Museum - DSC00063 cropped.jpg|thumb|upright=0.694|Fossilized shell of the Cretaceous marine bivalve Platyceramus]] †[[Platyceramus]]
 * †Platyceramus ahsenensis
 * †Platyceramus cycloides
 * †Platyceramus mantelli - or unidentified loosely related form
 * †Platyceramus platinus
 * †Platyognathus
 * †Plesiobaena
 * †Plesiobaena antiqua – or unidentified comparable form
 * †Polyonax – type locality for genus
 * †Polyonax mortuarius – type locality for species
 * †Preprismatoolithus
 * †Preprismatoolithus coloradensis
 * †Priacodon
 * †Priacodon fruitaensis – type locality for species
 * †Prionocyclus
 * †Probaena
 * †Probaena sculpta – type locality for species
 * Prognathodon overtoni.jpg †[[Prognathodon]]
 * †Prognathodon overtoni
 * †Prognathodon stadtmani – type locality for species
 * Propeamussium
 * †Propeamussium simplicus
 * †Protalphadon
 * †Protexanites
 * †Protexanites shoshonensis
 * †Protocardia
 * †Protocardia barneyi – type locality for species
 * †Protocupressinoxylon
 * †Protocupressinoxylon medlynii – type locality for species
 * †Protolambda
 * †Protolambda hatcheri
 * Protosphyraena2DB.jpg †[[Protosphyraena]]
 * Prunus
 * †Prunus corrugis
 * †Pseudaspidoceras
 * †Pseudaspidoceras collignoni
 * †Pseudobaculites
 * †Pseudocalycoceras
 * †Pseudocalycoceras angolaense
 * †Pseudocalycoceras dentonense
 * †Pseudoisurus
 * †Pseudoisurus tomosus – or unidentified comparable form
 * †Pseudoperna
 * †Pseudoperna bentonensis
 * †Pseudoperna congesta
 * †Pseudoperna inflatum – type locality for species
 * †Pseudotetrasauropus – tentative report
 * †Pteraichnus
 * †Ptychodus
 * †Ptychodus anonymus
 * †Ptychodus decurrens
 * †Ptychodus occidentalis
 * †Ptychodus whipplei
 * †Puebloites
 * †Puebloites spiralis
 * Pycnodonte
 * †Pycnodonte newberryi

R

 * †Rhaeboceras
 * †Rhaeboceras coloradoense – type locality for species
 * †Rhaeboceras halli
 * †Rhaeboceras subglobosum
 * Rhinobatos rhinobatos.jpg [[Rhinobatos]]
 * †Rhinobatos incertus
 * †Rhynchosauroides
 * †Rosselia
 * †Rotodactylus

S

 * †Sabalites
 * †Sabalites JC016 – informal
 * †Sabalites LA042 – informal
 * †Saurillodon
 * †Scapherpeton
 * †Scapherpeton tectum
 * SmallScaphites.jpg †[[Scaphites]]
 * †Scaphites binneyi
 * †Scaphites depressus
 * †Scaphites hippocrepis – or unidentified comparable form
 * †Scaphites nodosus
 * †Schadipes – type locality for genus
 * †Schadipes crypticus – type locality for species
 * †Sciponoceras
 * †Sciponoceras gracile
 * †Scoyenia
 * †Selaginella
 * †Selaginella JC023 – informal
 * Semionotus bergeri.jpg †[[Semionotus]]
 * †Solenoceras
 * †Solenoceras larimerense
 * †Solenoceras reesidei – or unidentified comparable form
 * †Solenoceras texanum
 * †Sphenodiscus
 * †Sphenodiscus pleurisepta
 * †Spiroxybeloceras
 * †Spiroxybeloceras meekanum
 * Squalicorax
 * †Squalicorax curvatus
 * †Squalicorax falcatus
 * †Squalicorax pristodontus
 * †Squatirhina
 * †Squatirhina americana
 * Stegosaurus stenops sophie wiki martyniuk.png †[[Stegosaurus]] – type locality for genus
 * †Stegosaurus armatus – type locality for species
 * †Stegosaurus stenops – type locality for species
 * †Stegosaurus ungulatus
 * †Steinerocaulis
 * †Steinerocaulis radiatus
 * †Stenomyti – type locality for genus
 * †Stenomyti huangae – type locality for species
 * †Stokesosaurus – or unidentified comparable form
 * †Stramentum
 * †Stramentum haworthi
 * Sulcoretusa
 * †Sulcoretusa dominici – type locality for species
 * †Sumitomoceras
 * †Sumitomoceras bentonianum
 * †Sumitomoceras conlini
 * Supersaurus NT crop.png †[[Supersaurus]] – type locality for genus
 * †Supersaurus vivianae – type locality for species
 * †Syncyclonema
 * †Syncyclonema travisanus
 * †Synorichthys – type locality for genus
 * †Synorichthys stewarti – type locality for species

T

 * †Tanaocrossus – type locality for genus
 * †Tanaocrossus kalliokoskii – type locality for species
 * †Tanocrossus
 * Tellina
 * †Tenea
 * †Tenea parilis
 * Teredo
 * †Teredo irregularis
 * †Texanites
 * †Texanites americanus
 * Thalassomedon.jpg †[[Thalassomedon]] – type locality for genus
 * †Thalassomedon hanningtoni – type locality for species
 * †Theiophytalia – type locality for genus
 * †Theiophytalia kerri – type locality for species
 * †Therangospodus – or unidentified comparable form
 * †Thescelosaurus
 * †Tibiaporrhais
 * †Tibiaporrhais cooperensis
 * †Titanosaurus
 * †Titanosaurus montanus – type locality for species
 * Torosaurus.tif †[[Torosaurus]]
 * †Torosaurus latus
 * †Torvosaurus – type locality for genus
 * †Torvosaurus tanneri – type locality for species
 * †Trachybaculites
 * †Trachybaculites columna – or unidentified comparable form
 * †Treptichnus
 * †Triceratops
 * †Triceratops galeus – type locality for species
 * †Triceratops horridus
 * †Trinacromerum – or unidentified comparable form
 * Trochocyathus
 * †Trochocyathus egerius
 * †Turbinopsis
 * Turritella
 * †Turseodus
 * †Turseodus dolorensis – type locality for species
 * †Tylosaurus
 * †Tylosaurus proriger
 * Tyrannosaurus Rex Holotype.jpg †[[Tyrannosaurus]]
 * †Tyrannosaurus rex

V

 * †Vanikoropsis
 * †Vanikoropsis nebrascensis
 * Vascoceratidae - Vascoceras cauvini.JPG †[[Vascoceras]]
 * †Vascoceras birchbyi
 * Viviparus
 * †Viviparus reesidei
 * †Volviceramus
 * †Volviceramus grandis
 * †Volviceramus involutus
 * †Voysa

W

 * †Walteria – type locality for genus
 * †Walteria jeffersonensis – type locality for species
 * †Walteria jeffersoni – type locality for species
 * †Watinoceras
 * †Watinoceras coloradoense – type locality for species
 * †Websteria
 * †Websteria cretacea
 * †Worthoceras

X

 * †Xenoxylon
 * †Xenoxylon moorei – type locality for species
 * XiphactinusDB cropped.png †[[Xiphactinus]]
 * †Xiphactinus audax

Z

 * †Zyziphus
 * †Zyziphus fibrillosus
 * †Zyziphus LA007 – informal
 * †Zyziphus LA032 – informal