# List of the Mesozoic life of Wyoming

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

## A

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* †Abielites
** †Abielites angusticarpus
* Illustration of a living Acipenser sturgeon Acipenser
** †Acipenser eruciferus
* †Acutostrea
** †Acutostrea plumosa
* †Adocus
* †Agathaumas – type locality for genus
** †Agathaumas sylvestris – type locality for species
* †Agerostrea
** †Agerostrea mesenterica
* †Agialopous – type locality for genus
** †Agialopous wyomingensis – type locality for species
* Restoration of the Cretaceous-Pleistocene amphibian Albanerpeton †Albanerpeton
** †Albanerpeton galaktion
** †Albanerpeton nexuosus – type locality for species
* †Albertosaurus – or unidentified comparable form
* †Alethesaurus – type locality for genus
** †Alethesaurus quadratus – type locality for species
* †Allacodon
** †Allacodon lentus – type locality for species
** †Allacodon pumilis – type locality for species
* †Allognathosuchus
* Life restoration of the Late Jurassic theropod dinosaur Allosaurus †Allosaurus – type locality for genus
** †Allosaurus fragilis – type locality for species
** †Allosaurus jimmadseni
* †Alostera
** †Alostera saskatchewanensis – type locality for species
* †Alphadon
** †Alphadon attaragos – type locality for species
** †Alphadon halleyi
** †Alphadon marshi
** †Alphadon sahnii
* †Altacreodus
** †Altacreodus magnus
* †Alzadites
** †Alzadites westonensis – type locality for species
* †Amblotherium – type locality for genus
** †Amblotherium gracilis – type locality for species
* †Amborellites – type locality for genus
** †Amborellites wyomingensis – type locality for species
* A living Amia, or bowfin Amia
** †Amia fragosa
** †Amia uintaensis
* †Amphicoelias
** †Amphicoelias brontodiplodocus – type locality for species
* †Amphidon – type locality for genus
** †Amphidon superstes – type locality for species
* †Anaklinoceras
** †Anaklinoceras mortoni
* †Anaschisma – type locality for genus
** †Anaschisma brachygnatha – type locality for species
** †Anaschisma browni – type locality for species
* †Anceptophyllum – type locality for genus
** †Anceptophyllum pulcrum – type locality for species
* †Anchura – tentative report
* †Ancorichnus
* †Andromeda
** †Andromeda grayana
* †Anemia
** †Anemia fremonti
** †Anemia subcretacea
* Restoration of the Late Triassic phytosaur Angistorhinus †Angistorhinus – type locality for genus
** †Angistorhinus aeolamnis – type locality for species
** †Angistorhinus gracilis – type locality for species
** †Angistorhinus grandis – type locality for species
** †Angistorhinus maximus – type locality for species
* †Anisoceras
* †Anisomyon
** †Anisomyon borealis
** †Anisomyon centrale
** †Anisomyon patelliformis
** †Anisomyon subovatus – or unidentified related form
** †Anisomyon subovulatus
* †Ankistrorhynchus
** †Ankistrorhynchus washakiensis – type locality for species
* Life restoration of the Late Cretaceous armored dinosaur Ankylosaurus †Ankylosaurus
** †Ankylosaurus magniventris
* †Anomalofusus – tentative report
* Anomia
** †Anomia tellinoides
* Anona
** †Anona robusta – tentative report
* †Anthrotaxopsis
** †Anthrotaxopsis tenuicaulis
* Antrimpos
* †Apatodonosaurus
** †Apatodonosaurus grayi
* †Apatosaurinae
** †Apatosaurinae – type locality for genus – informal
* Life restoration of the Late Jurassic sauropod dinosaur Apatosaurus †Apatosaurus
** †Apatosaurus louisae
** †Apatosaurus minimus
* †Apeibopsis – tentative report
** †Apeibopsis discolor
* †Aploconodon – type locality for genus
** †Aploconodon comoensis – type locality for species
* Aporrhais
** †Aporrhais biangulata
* †Aquilina – type locality for genus
** †Aquilina grossidentata – type locality for species
* Aralia
** †Aralia veatchii
* †Araliaephyllum
** †Araliaephyllum artocarpoides
* Foliage and cones of a living Araucaria tree Araucaria
* †Araucarites
** †Araucarites cuneatus – type locality for species
** †Araucarites longifolia
** †Araucarites wyomingensis – type locality for species
* Arca – report made of unidentified related form or using admittedly obsolete nomenclature
* †Arcellites
** †Arcellites disciformis
* †Archaeotriakis
** †Archaeotriakis ornatus – type locality for species
** †Archaeotriakis rochelleae
* †Archaeotrigon – type locality for genus
** †Archaeotrigon brevimaxillus – type locality for species
* Fossilized shells of the Middle Jurassic ammonoid cephalopod Arcticoceras †Arcticoceras
* †Arenicolites
* †Aristolochites
** †Aristolochites brittoni
* †Ascarinites – type locality for genus
** †Ascarinites communis – type locality for species
* Aspideretes
* †Aspideretoides
** †Aspideretoides foveatus – or unidentified comparable form
* †Asplenites
** †Asplenites tenellum
* A living Asplenium, or spleenwort †Asplenium
** †Asplenium haguei
** †Asplenium neomexicanum
** †Asplenium occidentale
* †Astandes
** †Astandes densatus
* †Astarta
** †Astarta packardi
* Astarte
** †Astarte gregaria
** †Astarte livingstonensis
** †Astarte meeki
** †Astarte morion
* †Athrotaxopsis
** †Athrotaxopsis tenuicaulis
* † Atira – tentative report
** †Atira nebrascensis
* †Atokatheridium – or unidentified comparable form
* Illustration of fossilized teeth from the Late Cretaceous tyrannosaur Aublysodon †Aublysodon
** †Aublysodon mirandus
* †Austrotindaria
** †Austrotindaria antiqua
** †Austrotindaria canalensis
** †Austrotindaria svalbardensis
* †Avernalia – type locality for genus
** †Avernalia solida – type locality for species

## B

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* Fossilized shell of the Late Cretaceous ammonoid cephalopod Baculites †Baculites
** †Baculites asper
** †Baculites asperiformis
** †Baculites baculus
** †Baculites clinolobatus
** †Baculites cobbani
** †Baculites codyensis
** †Baculites crickmayi
** †Baculites elaisi
** †Baculites eliasi
** †Baculites gilberti
** †Baculites grandis
** †Baculites gregoryensis
** †Baculites haresi
** †Baculites jenseni – or unidentified comparable form
** †Baculites mariasensis
** †Baculites mclearni
** †Baculites obtusus
** †Baculites perplexus
** †Baculites reesidei
** †Baculites rugosus
** †Baculites scotti
* †Baena
** †Baena hatcheri – type locality for species
** †Baena hayi – type locality for species
** †Baena marshi – type locality for species
* †Baieropsis
** †Baieropsis adiantifolia
** †Baieropsis pluripartita
* †Baptanodon
** †Baptanodon discus
** †Baptanodon reedi – type locality for species
** †Baptanodon robustus – type locality for species
* Barbatia – tentative report
* Restoration of the Late Jurassic sauropod dinosaur Barosaurus rearing to defend itself against a pair of the theropod Allosaurus †Barosaurus
** †Barosaurus lentus
* †Basilemys
** †Basilemys sinuosa
* †Batodon
** †Batodon tenuis – type locality for species
* †Belonostomus
** †Belonostomus longirostris
* Berenicea
* Bombur
* †Borealosuchus
** †Borealosuchus sternbergii – type locality for species
* †Boremys
* †Borissiakoceras
** †Borissiakoceras orbiculatum
* Botula
** †Botula ripleyana
* A living Brachaelurus, or blind shark Brachaelurus
** †Brachaelurus bighornensis – type locality for species
* †Brachiosaurus
* †Brachybrachium – type locality for genus
** †Brachybrachium brevipes – type locality for species
* †Brachychampsa
** †Brachychampsa montana
* †Brachyphyllum
** †Brachyphyllum crassum
* †Brontopodus – or unidentified comparable form
** †Brontopodus birdi
* Life restoration of a herd of the Late Jurassic sauropod dinosaur Brontosaurus †Brontosaurus – type locality for genus
** †Brontosaurus excelsus – type locality for species
** †Brontosaurus parvus – type locality for species
** †Brontosaurus yahnahpin – type locality for species
* †Bryceomys
* †Bullopsis
** †Bullopsis cretacea – or unidentified related form

## C

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* †Cadoceras
* Callista
** †Callista deweyi
** †Callista peplucida
* †Calycoceras
** †Calycoceras canitaurinum
* Life restoration of a herd of the Late Jurassic sauropod dinosaur Camarasaurus †Camarasaurus – type locality for genus
** †Camarasaurus grandis – type locality for species
** †Camarasaurus lentus – type locality for species
* †Camborygma
* Campeloma
* †Camptomus
** †Camptomus amplus – type locality for species
* †Camptonectes
** †Camptonectes bellistriatus
** †Camptonectes distans – or unidentified comparable form
** †Camptonectes platessiformis
** †Camptonectes stygius
* Life restoration of the Late Jurassic ornithopod dinosaur Camptosaurus †Camptosaurus
** †Camptosaurus dispar – type locality for species
* † Canna
** †Canna magnifolia – tentative report
* †Capillirhynchia
** †Capillirhynchia gallatinensis – type locality for species
* Cardium sp.
* †Carpites
** †Carpites lancensis
** †Carpites verrucosus
** †Carpites walcotti
* †Carpolithus
** †Carpolithus barrensis – type locality for species
** †Carpolithus fasciculatus
** †Carpolithus foenarius – type locality for species
** †Carpolithus montiumnigrorum – type locality for species
** †Carpolithus virginiensis
* †Carthaginites
** †Carthaginites aquilonius – type locality for species
* †Cataceramus
** †Cataceramus tenuilineatus
* †Cedrobaena
** †Cedrobaena brinkman
* †Celastrophyllum
** †Celastrophyllum gyminaefolium
* Foliage and fruit of a living Celastrus, or staff vine †Celastrus – tentative report
** †Celastrus taurinensis
* †Cemeterius – type locality for genus
** †Cemeterius monstrosus – type locality for species
* †Centrophoroides
** †Centrophoroides worlandensis – type locality for species
* †Cephalotaxopsis
** †Cephalotaxopsis magnifolia
* †Ceramornis – type locality for genus
** †Ceramornis major – type locality for species
* †Ceratodus
** †Ceratodus frazieri
** †Ceratodus guentheri
* Restoration of the Late Jurassic ceratosaur Ceratosaurus †Ceratosaurus
* Cercidiphyllum
** †Cercidiphyllum arcticum
** †Cercidiphyllum ellipticum
* †Cercomya
** †Cercomya punctata
* †Ceritella
* Cerithium – tentative report
* †Chamops – type locality for genus
** †Chamops segnis – type locality for species
* Life restoration of the Late Cretaceous-Eocene choristoderan reptile Champsosaurus †Champsosaurus
** †Champsosaurus natator
* †Chelonipus – or unidentified comparable form
* Chiloscyllium
** †Chiloscyllium missouriense
* †Chirotherium
** †Chirotherium barthii
* Chlamys
** †Chlamys nebrascensis
* †Chondroceras
* †Cimexomys
** †Cimexomys minor
* †Cimolestes
** †Cimolestes incisus – type locality for species
** †Cimolestes stirtoni – type locality for species
* †Cimolodon
** †Cimolodon nitidus – type locality for species
** †Cimolodon peregrinus – type locality for species
* Life restoration of the face of the Late Cretaceous multituberculate mammal Cimolomys †Cimolomys
** †Cimolomys clarki
** †Cimolomys gracilis – type locality for species
** †Cimolomys parvus – type locality for species
* †Cimolopteryx
** †Cimolopteryx maxima – type locality for species
** †Cimolopteryx rara
* Cinnamomum
** †Cinnamomum hesperium
* †Cissitis
** †Cissitis rocklandensis
* Cissus
** †Cissus lobato-crenata – tentative report
* †Cladoceramus
** †Cladoceramus undulatoplicatus – or unidentified related form
* Fossilized foliage of the Permian-Late Cretaceous fern Cladophlebis Cladophlebis
** †Cladophlebis parva
** †Cladophlebis readi – type locality for species
** †Cladophlebis readii
** †Cladophlebis wyomingensis – type locality for species
* †Claraia
** †Claraia clarai
** †Claraia mulleri
** †Claraia stachei
* †Clemensodon – type locality for genus
** †Clemensodon megaloba – type locality for species
* †Clioscaphites
** †Clioscaphites saxitonianus
** †Clioscaphites vermiformis
* †Coahuilites
** †Coahuilites sheltoni
* †Coelostylina
* †Coelosuchus – type locality for genus
** †Coelosuchus reedii – type locality for species
* Diagram illustrating the known fossil material of the Late Jurassic theropod dinosaur Coelurus †Coelurus – type locality for genus
** †Coelurus fragilis – type locality for species
* †Collignoniceras
** †Collignoniceras woollgari
* †Colpodontosaurus – type locality for genus
** †Colpodontosaurus cracens – type locality for species
* †Comobatrachus – type locality for genus
** †Comobatrachus aenigmaticus – type locality for species
* †Comodactylus – type locality for genus
** †Comodactylus ostromi – type locality for species
* †Comodon – type locality for genus
** †Comodon gidleyi – type locality for species
* †Comonecturoides – type locality for genus
** †Comonecturoides marshi – type locality for species
* †Comotherium – type locality for genus
** †Comotherium richi – type locality for species
* †Compsemys
** †Compsemys victa
* †Confusionella
** †Confusionella loczyi – type locality for species
* Illustration of fossilized vertebrae of the Late Cretaceous-Eocene snake Coniophis. Othniel Charles Marsh (1892). †Coniophis – type locality for genus
** †Coniophis precedens – type locality for species
* †Coniopteris – tentative report
* †Contogenys – or unidentified comparable form
* †Corax
* †Corbicella – tentative report
* Corbula
** †Corbula crassimarginata
** †Corbula kanabensis
** †Corbula munda
* †Coriops
** †Coriops amnicolus
* †Cornophyllum
** †Cornophyllum wardii
* Life restoration of the Early Triassic plesiosaur relative Corosaurus †Corosaurus
** †Corosaurus alcovensis
* Cossmannea
* Crassatella
** †Crassatella evansi
* †Crassidenticulum
** †Crassidenticulum aquilae – type locality for species
** †Crassidenticulum decurrens
* Crenella
* †Cretorectolobus
** †Cretorectolobus olsoni
* †Cryptometoicoceras – type locality for genus
** †Cryptometoicoceras mite – type locality for species
* †Cryptorhytis
** †Cryptorhytis cheyennensis
* †Ctenacodon – type locality for genus
** †Ctenacodon laticeps – type locality for species
** †Ctenacodon scindens – type locality for species
** †Ctenacodon serratus – type locality for species
* †Cteniogenys – type locality for genus
** †Cteniogenys antiquus – type locality for species
* †Ctenostreon
** †Ctenostreon gikshanensis – or unidentified comparable form
* Shell of a Cucullaea, or false ark shell Cucullaea
** †Cucullaea haguei
** †Cucullaea shumardi
* †Cunningtoniceras
* Cuspidaria
** †Cuspidaria variablis
* †Cycadeospermum
** †Cycadeospermum rotundatum
* †Cyclurus
** †Cyclurus fragosus
* †Cylindricum
* †Cymbophora
** †Cymbophora canonensis – or unidentified comparable form
** †Cymbophora formosa
** †Cymbophora holmesi
* †Cyperacites
* †Czekanowskia
** †Czekanowskia nervosa

## D

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* †Dakotasaurus – type locality for genus
** †Dakotasaurus browni – type locality for species
* †Daspletosaurus
* Life restoration of the Early Cretaceous dromaeosaur ("raptor") Deinonychus †Deinonychus
** †Deinonychus antirrhopus
* †Delphodon
** †Delphodon comptus – type locality for species
* †Deltatheroides – or unidentified comparable form
* †Dennstaedtia
** †Dennstaedtia fremonti
* Dentalium
** †Dentalium gracile
** †Dentalium pauperculum
* †Derrisemys
** †Derrisemys sterea
* Restoration of the Late Triassic aetosaur Desmatosuchus with an anachronistic human to scale †Desmatosuchus
* †Desmoscaphites
** †Desmoscaphites bassleri
* †Dewalquea
** †Dewalquea pulchella
* †Diastopora
** †Diastopora cutleri – type locality for species
* †Dicellonema
** †Dicellonema abrekensis
* †Dicotyledon
* Life restoration of the Late Cretaceous marsupial relative Didelphodon †Didelphodon
** †Didelphodon vorax – type locality for species
* †Didymoceras
** †Didymoceras nebrascense
** †Didymoceras stevensoni
* †Dillenites
** †Dillenites cleburni
* †Dinochelys
** †Dinochelys whitei
* †Diospyros
** †Diospyros stenosepala
* †Diploconcha
* †Diplocraterion
* †Diplodocinae
** †Diplodocinae – type locality for genus – informal
* Life restoration of the Late Jurassic long-necked dinosaur Diplodocus †Diplodocus
** †Diplodocus carnegii – type locality for species
** †Diplodocus hallorum
** †Diplodocus longus
* †Discoscaphites
* †Docodon – type locality for genus
** †Docodon affinis – type locality for species
** †Docodon crassus – type locality for species
** †Docodon striatus – type locality for species
** †Docodon superus – type locality for species
** †Docodon victor – type locality for species
* †Dolichobrachium – type locality for genus
** †Dolichobrachium gracile – type locality for species
* Mounted fossilized skeleton of the Late Cretaceous plesiosaur Dolichorhynchops †Dolichorhynchops
** †Dolichorhynchops osborni
* †Dombeyopsis
** †Dombeyopsis colgatensis
** †Dombeyopsis obtusa
** †Dombeyopsis platanoides
** †Dombeyopsis trivialis
* †Doratodon – tentative report
* †Dorsetisaurus
* †Dosiniopsis
** †Dosiniopsis deweyi
* †Drepanocheilus
** †Drepanocheilus evansi
** †Drepanocheilus nebrascensis
** †Drepanocheilus obesus
** †Drepanocheilus scotti – or unidentified comparable form
* †Drinker – type locality for genus
** †Drinker nisti – type locality for species
* Life restoration of the Late Cretaceous "raptor" Dromaeosaurus †Dromaeosaurus
* †Dryandroides
** †Dryandroides lanceolata
* †Dryolestes – type locality for genus
** †Dryolestes priscus – type locality for species
** †Dryolestes vorax
* †Dryophyllum – type locality for genus
** †Dryophyllum lanceolatum
** †Dryophyllum polymorphum – type locality for species
** †Dryophyllum subfalcatum
* Dryopteris
** †Dryopteris coloradensis
* †Dryosaurus
** †Dryosaurus altus – type locality for species
* †Dryptosaurus – or unidentified comparable form
* †Dunveganoceras
** †Dunveganoceras pondi
** †Dunveganoceras problematicum
* †Dyslocosaurus – type locality for genus
** †Dyslocosaurus polyonychius – type locality for species

## E

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* †Echidnocephalus – tentative report
* †Edmontonia
** †Edmontonia rugosidens – or unidentified comparable form
* †Edmontosaurus
** Life restoration of the Late Cretaceous duck-billed dinosaur Edmontosaurus annectens †Edmontosaurus annectens – type locality for species
* †Egertonodus
* †Elaphrosaurus – tentative report
* †Elasmosaurus
* †Elatides
* †Ellipsoscapha
** †Ellipsoscapha occidentalis
* †Emarginachelys
* †Empo
* †Enneabatrachus – type locality for genus
** †Enneabatrachus hechti – type locality for species
* Entalis
** †Entalis paupercula – tentative report
* †Entalophora
** †Entalophora stokesi – type locality for species
* †Eobatrachus – type locality for genus
** †Eobatrachus agilis – type locality for species
* †Eocephalites
** †Eocephalites primus
* †Eokainaster – type locality for genus
** †Eokainaster pewei
* Fossilized skeleton of the Eocene-Pliocene frog Eopelobates †Eopelobates
* †Equisetites
* †Equisetum
** †Equisetum FF014 – informal
** †Equisetum RS016 – informal
** †Equisetum virginicum
* †Essonodon
** †Essonodon browni
* †Estescincosaurus – type locality for genus
** †Estescincosaurus cooki – type locality for species
* †Eubaena – type locality for genus
** †Eubaena cephalica – type locality for species
* Fossilized shell of the Late Cretaceous ammonoid cephalopod Eubostrychoceras †Eubostrychoceras
** †Eubostrychoceras matsumotoi – type locality for species
* †Eubrachiosaurus – type locality for genus
** †Eubrachiosaurus browni – type locality for species
* †Eucalycoceras
** †Eucalycoceras templetonense
* †Eucrossorhinus
** †Eucrossorhinus microcuspidatus
* †Eumorphotis
** †Eumorphotis multiformis
* †Euomphaloceras
** †Euomphaloceras merewetheri
* †Eurysalenia
** †Eurysalenia minima
* †Euspira
** †Euspira obliquata
* †Euthlastus – type locality for genus
** †Euthlastus cordiformis – type locality for species
* Illustration in multiple views of a fossilized shell of the Late Jurassic-Miocene nautiloid cephalopod Eutrephoceras †Eutrephoceras
** †Eutrephoceras montanaense
* †Eutretauranosuchus
** †Eutretauranosuchus delfsi
* †Exiteloceras
** †Exiteloceras jenneyi
* †Exogyra
** †Exogyra costata
* †Exostinus – type locality for genus
** †Exostinus lancensis – type locality for species

## F

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* †Falepetrus
** †Falepetrus barwini – type locality for species
* Shell of a Fasciolaria, or tulip sea snail Fasciolaria
** †Fasciolaria flexicostata – tentative report
* †Feistmantelia – type locality for genus
** †Feistmantelia oblonga – type locality for species
* †Ficophyllum
** †Ficophyllum serratum
* Ficus
** †Ficus fremonti
** †Ficus Fremontii
** †Ficus inaequalis
** †Ficus paryearensis
** †Ficus planicosta
** †Ficus planicostata
** †Ficus rockvalensis
** †Ficus trinervis
* †Filicites
** †Filicites knowltoni
* †Forresteria
** †Forresteria stantoni
* Known material diagram of the Late Jurassic ceratosaur Fosterovenator †Fosterovenator – type locality for genus
** †Fosterovenator churei – type locality for species
* †Foxraptor – type locality for genus
** †Foxraptor atrox – type locality for species
* †Fraxinus
** †Fraxinus denticulata
** †Fraxinus leii

## G

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* T
* U
* V
* W
* X
* Y
* Z
* Fossilized skull of the Late Jurassic long-necked dinosaur Galeamopus †Galeamopus
** †Galeamopus hayi
** †Galeamopus pabsti – type locality for species
* †Gargoyleosaurus
** †Gargoyleosaurus parkpinorum
* †Geinitzia
** †Geinitzia Jenneyi – type locality for species
* †Geonomites
** †Geonomites schimperi
* Gerrhonotus – or unidentified comparable form
* †Gervillaria
** †Gervillaria montanaensis
* †Gervillia
** †Gervillia dolabrata
** †Gervillia ussurica – or unidentified comparable form
* †Gilmoremys
** †Gilmoremys lancensis – type locality for species
* Ginglymostoma
** †Ginglymostoma globidens
* Fossilized leaf of the Permian-modern tree Ginkgo Ginkgo
** †Ginkgo adiantoides – tentative report
* †Glasbius
** †Glasbius intricatus – type locality for species
* †Gleichenites
** †Gleichenites sepulta
* †Glyptops – type locality for genus
** †Glyptops pervicax
** †Glyptops plicatulus – type locality for species
* Glyptostrobus
** †Glyptostrobus brookensis
* Mounted fossilized skeleton of the Middle Jurassic-Late Cretaceous mammal Gobiconodon †Gobiconodon
** †Gobiconodon ostromi
* †Goniomya
** †Goniomya montanaensis
* †Goniopholis
* †Gracilimanus
** †Gracilimanus obscurus
* †Grammatodon
** †Grammatodon haguei
* †Graphidula
** †Graphidula alleni – or unidentified comparable form
** Interior and exterior of a fossilized shell of the Late Triassic-Eocene marine bivalve Gryphaea †Graphidula culbertsoni
* †Grewiopsis
** †Grewiopsis saportana
* †Gryphaea
** †Gryphaea nebrascensis
** †Gryphaea planoconvexa
* †Gypsonictops
** †Gypsonictops hypoconus – type locality for species
** †Gypsonictops lewisi
* †Gypsonicus
** †Gypsonicus wyomingensis

## H

* A
* B
* C
* D
* E
* F
* G
* H
* I
* J
* K
* L
* M
* N
* O
* P
* Q
* R
* S
* T
* U
* V
* W
* X
* Y
* Z
* †Habrosaurus – type locality for genus
** †Habrosaurus dilatus – type locality for species
* †Hadrosauropodus
* †Halymenites
** †Halymenites major
* †Hamites
** †Hamites cimarronensis
** †Hamites novimexicanus
** †Hamites salebrosus
* Life restoration of the Late Jurassic sauropod dinosaur Haplocanthosaurus †Haplocanthosaurus
* †Haptosphenus – type locality for genus
** †Haptosphenus placodon – type locality for species
* †Haresiceras
** †Haresiceras natronense
* †Harpactognathus – type locality for genus
** †Harpactognathus gentryii – type locality for species
* †Hatcheritherium – type locality for genus
** †Hatcheritherium alpha – type locality for species
* †Hausmannia
** †Hausmannia AF017
* †Helopanoplia
** †Helopanoplia distincta
* Hemiaster
** †Hemiaster humphreysanus
* Known material diagram of the Middle-Late Triassic distant crocodilian relative Heptasuchus †Heptasuchus – type locality for genus
** †Heptasuchus clarki – type locality for species
* †Herpetarius
** †Herpetarius humilis
* †Hesperornithoides – type locality for genus
** †Hesperornithoides miessleri – type locality for species
* †Hesperosaurus – type locality for genus
** †Hesperosaurus mjosi – type locality for species
* †Heteroceras
** †Heteroceras cochleatum – tentative report
* †Homomya
** †Homomya gallatinensis
* †Hoploscaphites
** †Hoploscaphites birkelundae – type locality for species
** †Hoploscaphites gilli
** †Hoploscaphites macer
** †Hoploscaphites nodosus
** †Hoploscaphites plenus
** †Hoploscaphites quadrangularis
* †Hummelichelys
** †Hummelichelys beecheri – type locality for species
* Life restoration of the Late Triassic rhynchosaur Hyperodapedon †Hybodus
** †Hybodus montanensis
** †Hybodus wyomingensis – type locality for species
* †Hyperodapedon
** †Hyperodapedon sanjuanensis – or unidentified comparable form
* †Hypotodus
** †Hypotodus grandis
* †Hypsodon – tentative report
** †Hypsodon radiatulus

## I

* A
* B
* C
* D
* E
* F
* G
* H
* I
* J
* K
* L
* M
* N
* O
* P
* Q
* R
* S
* T
* U
* V
* W
* X
* Y
* Z
* Life restoration of the Late Cretaceous bony fish Ichthyodectes †Ichthyodectes
* †Icthyodectes – tentative report
* †Icthyodesctes – tentative report
* †Idiohamites
** †Idiohamites bispinosus
* †Iguanavus
** †Iguanavus teres – type locality for species
* Fossilized shell of the Early Jurassic-Late Cretaceous marine bivalve Inoceramus with a human indicating its size †Inoceramus
** †Inoceramus agdjakendensis – or unidentified comparable form
** †Inoceramus americanus – type locality for species
** †Inoceramus anglicus
** †Inoceramus balchii
** †Inoceramus barabini
** †Inoceramus crispii
** †Inoceramus deformis
** †Inoceramus dimidius
** †Inoceramus erectus – or unidentified related form
** †Inoceramus fibrosus
** †Inoceramus fragilis – or unidentified related form
** †Inoceramus gibbosus
** †Inoceramus glacierensis
** †Inoceramus grandis
** †Inoceramus incurvus
** †Inoceramus lundbreckensis
** †Inoceramus perplexus
** †Inoceramus prefragilis
** †Inoceramus proximus – or unidentified related form
** †Inoceramus sagensis
** †Inoceramus subcircularis
** †Inoceramus subcompressus
** †Inoceramus sublaevis
** †Inoceramus tenuirostratus
** †Inoceramus tenuiumbonatus – or unidentified comparable form
** †Inoceramus turgidus – or unidentified related form
** †Inoceramus typicus
** †Inoceramus umbonatus
** †Inoceramus undabundus
* †Ischyrhiza
** Fossilized shell of the Permian-modern marine bivalve Isognomon †Ischyrhiza avonicola – type locality for species
** †Ischyrhiza basinensis – type locality for species
** †Ischyrhiza mira
* Isocrinus
** †Isocrinus knighti
** †Isocrinus wyomingensis
* †Isocyprina
** †Isocyprina cinnabarensis
* Isognomon
** †Isognomon perplana – or unidentified comparable form
* Isurus – tentative report

## J

* A
* B
* C
* D
* E
* F
* G
* H
* I
* J
* K
* L
* M
* N
* O
* P
* Q
* R
* S
* T
* U
* V
* W
* X
* Y
* Z
* †Janumys
* †Jeletzkytes
** †Jeletzkytes dorfi – type locality for species
* †Jensensispermum
* †Judithemys
** †Judithemys backmani

## K

* A
* B
* C
* D
* E
* F
* G
* H
* I
* J
* K
* L
* M
* N
* O
* P
* Q
* R
* S
* T
* U
* V
* W
* X
* Y
* Z
* †Kaatedocus – type locality for genus
** †Kaatedocus siberi – type locality for species
* †Koskinonodon – type locality for genus
** †Koskinonodon perfectus – type locality for species

## L

* A
* B
* C
* D
* E
* F
* G
* H
* I
* J
* K
* L
* M
* N
* O
* P
* Q
* R
* S
* T
* U
* V
* W
* X
* Y
* Z
* †Lamarqueavis
** †Lamarqueavis minima – type locality for species
** †Lamarqueavis petra – type locality for species
* †Lamiasaura – type locality for genus
** †Lamiasaura ferox – type locality for species
* †Lanceosaurus – type locality for genus
** †Lanceosaurus compressus – type locality for species
** †Lanceosaurus hatcheri – type locality for species
* †Laolestes – type locality for genus
** †Laolestes eminens – type locality for species
** †Laolestes goodrichi – type locality for species
** †Laolestes oweni – type locality for species
* †Laopteryx – type locality for genus
** †Laopteryx priscus – type locality for species
* †Laosaurus – type locality for genus
** †Laosaurus celer – type locality for species
* †Laurophyllum
** †Laurophyllum coloradensis
** †Laurophyllum meeki
** †Laurophyllum salicifolium
** †Laurophyllum wardiana
* Laurus
** †Laurus aspensis – type locality for species
* †Lepidotes – or unidentified related form
* Lepisosteus
** †Lepisosteus occidentalis
* †Leptalestes
** †Leptalestes cooki – type locality for species
** †Leptalestes krejcii
* Life restoration of the Late Cretaceous primitive horned dinosaur Leptoceratops †Leptoceratops
** †Leptoceratops gracilis
* †Leptochamops
** †Leptochamops denticulatus – type locality for species
** †Leptochamops thrinax
* †Leptochondria
** †Leptochondria occidanea
* †Leptostrobus
** †Leptostrobus alatus – type locality for species
** †Leptostrobus longifolia
** †Leptostrobus longifolius
* †Lesterwardia – type locality for genus
** †Lesterwardia palustris – type locality for species
* †Leucichthyops
** †Leucichthyops vagans
* †Leucicthyops
** †Leucicthyops vagans
* Lima
** †Lima occidentalis
* Lingula
** †Lingula nitida – or unidentified comparable form
* †Lingularia
** †Lingularia borealis
* †Lioplacodes – or unidentified comparable form
* †Liostrea
** †Liostrea strigilecula
* Liquidambar
** †Liquidambar fontanella – type locality for species
* †Lisserpeton
** †Lisserpeton bairdi
* Electron micrograph of fossilized teeth from the Early Jurassic-Early Cretaceous freshwater shark Lissodus †Lissodus
** †Lissodus griffisi – type locality for species
* †Litakis – type locality for genus
** †Litakis gilmorei – type locality for species
* †Lonchidion – type locality for genus
** †Lonchidion selachos – type locality for species
* †Lonchisaurus – type locality for genus
** †Lonchisaurus trichurus – type locality for species
* †Lonchodytes – type locality for genus
** †Lonchodytes estesi – type locality for species
** †Lonchodytes pterygius – type locality for species
* †Lophochelys
* A living Lunatia moon sea snail Lucina
** †Lucina mattiformis – or unidentified comparable form
** †Lucina occidentalis
** †Lucina subundata
* Lunatia – tentative report
* Lygodium
** †Lygodium AF030 – informal
* †Lyosoma
** †Lyosoma powelli

## M

* A
* B
* C
* D
* E
* F
* G
* H
* I
* J
* K
* L
* M
* N
* O
* P
* Q
* R
* S
* T
* U
* V
* W
* X
* Y
* Z
* Diagram illustrating the known fossil material of two specimens of the Late Jurassic crocodile relative Macelognathus †Macelognathus – type locality for genus
** †Macelognathus vagans – type locality for species
* Mactra
** †Mactra emmonsi
* †Mactromya – tentative report
* †Magadiceramus
** †Magadiceramus soukupi
** †Magadiceramus subquadratus
* †Magnoliophyllum
** †Magnoliophyllum cordatum
* †Malapoenna
** †Malapoenna weediana – tentative report
* Malletia
** †Malletia stephensoni
* †Manihotites
** †Manihotites georgiana
* †Martinectes
** †Martinectes bonneri – type locality for species
* †Matonidium
** †Matonidium Althaausii
** †Matonidium Althausii
* †Mecochirus
* Life restoration of the Late Jurassic plesiosaur Megalneusaurus †Megalneusaurus
** †Megalneusaurus rex – type locality for species
* †Megasphaeroceras
** †Megasphaeroceras rotundum – or unidentified comparable form
* †Meleagrinella
** †Meleagrinella curta
* †Melvius
** †Melvius thomasi
* †Meniscoessus
** †Meniscoessus gracilis – type locality for species
** †Meniscoessus intermedius
** †Meniscoessus robustus – type locality for species
** †Meniscoessus seminoensis – type locality for species
* †Meniscognathus – type locality for genus
** †Meniscognathus altmani – type locality for species
* †Menispermites
** †Menispermites belli
** †Menispermites cockerelli
** †Menispermites knightii
* Assemblage of fossilized shells of the Late Cretaceous ammonoid cephalopod Menuites †Menuites
** †Menuites complexus
* †Mesembrioxylon
* †Mesodma
** †Mesodma formosa
** †Mesodma hensleighi
** †Mesodma primaeva
** †Mesodma thompsoni – type locality for species
* †Metaptychoceras
* †Metoicoceras
** †Metoicoceras geslinianum
** †Metoicoceras mosbyense – or unidentified comparable form
** †Metoicoceras praecox
* †Micrabacia
** †Micrabacia radiata
* †Microtaenia
** †Microtaenia paucifolia
** †Microtaenia variabilis
* Life restoration of the Early Cretaceous oviraptorosaur Microvenator †Microvenator
** †Microvenator celer
* †Minerisporites
** †Minerisporites pseudorichardsonii
* Modiolus
** †Modiolus meekii
** †Modiolus subimbricatus
* †Montania – type locality for genus
** †Montania glandulosa – type locality for species
* †Moremanoceras
** †Moremanoceras costatum
** †Moremanoceras scotti
* †Moriconia
** †Moriconia cyclotoxon
* †Morosaurus
* †Myalina
** †Myalina postcarbonica
* †Myledaphus
** †Myledaphus bipartitus
* Fossilized shell of the Jurassic-Cretaceous marine bivalve Myophorella †Myophorella
** †Myophorella yellowstonensis
* Myrica
** †Myrica bolanderi – tentative report
** †Myrica nervosa
* †Myrtophyllum
** †Myrtophyllum torreyi
* †Mytiloides
** †Mytiloides stantoni
* †Mytilus
** †Mytilus whitei

## N

* A
* B
* C
* D
* E
* F
* G
* H
* I
* J
* K
* L
* M
* N
* O
* P
* Q
* R
* S
* T
* U
* V
* W
* X
* Y
* Z
* †Nageiopsis
** †Nageiopsis angustifolia
** †Nageiopsis longifolia
* †Nanocuris
** †Nanocuris improvida
* †Nanomyops
* †Nanosaurus
** †Nanosaurus rex
* †Nanotyrannus – tentative report
* †Naomichelys
** †Naomichelys speciosa
* A living Nelumbo lotus †Nelumbo
** †Nelumbo weymouthi – type locality for species
** †Nelumbo weymouthii
* †Nemocardium
** †Nemocardium parahillanum
* †Nemodon
** †Nemodon eufalensis
** †Nemodon grandis
* †Neocardioceras
** †Neocardioceras laevigatum – type locality for species
** †Neocardioceras minutum – type locality for species
** †Neocardioceras transiens
** †Neocardioceras uptonense – type locality for species
* †Neogastroplites
** †Neogastroplites wyomingensis
* †Neonereites – or unidentified comparable form
** †Neonereites biserialis
* †Neoplagiaulax
* †Neoschizodus
** †Neoschizodus laevigatus
* †Nerinea – tentative report
* †Neurankylus
** †Neurankylus wyomingensis – type locality for species
* †Nilsonia
** †Nilsonia mehli
** †Nilsonia nigricollensis
* Nodosaria
* Historical reconstruction of the holotype skeleton from 1921 †Nodosaurus – type locality for genus
** †Nodosaurus textilis – type locality for species
* †Nonactaeonina
** †Nonactaeonina attenuata
* †Normannites – tentative report
** †Normannites crickmayi – or unidentified comparable form
* †Nortedelphys
** †Nortedelphys jasoni
** †Nortedelphys magnus
** †Nortedelphys minimus
* Interior of a fossilized shell of the Early Ordovician-modern marine bivalve Nucula Nucula
** †Nucula cancellata
** †Nucula nacatochana
** †Nucula planimarginata
* Nuculana
** †Nuculana bisulcata
** †Nuculana corsicana
** †Nuculana equilateralis – tentative report
** †Nuculana evansi
** †Nuculana pittensis
* †Nymphaeites
** †Nymphaeites dawsoni

## O

* A
* B
* C
* D
* E
* F
* G
* H
* I
* J
* K
* L
* M
* N
* O
* P
* Q
* R
* S
* T
* U
* V
* W
* X
* Y
* Z
* †Obamadon
** †Obamadon gracilis
* †Obnixia – type locality for genus
** †Obnixia thaynesiana
* †Odaxosaurus – type locality for genus
** †Odaxosaurus piger – type locality for species
* A living Odontaspis sand shark Odontaspis
** †Odontaspis cheathami – type locality for species
** †Odontaspis steineri – type locality for species
* †Oklatheridium
** †Oklatheridium wiblei
* †Oligoptycha
** †Oligoptycha concinna
* †Omasaria
* †Onoclea
** †Onoclea minima
* †Opertochasma
* †Ophiopsis
* †Ophthalmosaurus
** †Ophthalmosaurus natans
* †Opisthias
** †Opisthias rarus – type locality for species
* †Opisthotriton
** †Opisthotriton kayi
* Mounted fossilized skeleton of the Late Jurassic theropod dinosaur Ornitholestes †Ornitholestes – type locality for genus
** †Ornitholestes hermanni – type locality for species
* †Ornithomimus
** †Ornithomimus minutus
** †Ornithomimus sedens – type locality for species
** †Ornithomimus velox – or unidentified comparable form
* †Orthotrigonia
** †Orthotrigonia sohli – tentative report
* †Osmakasaurus – tentative report
** †Osmakasaurus depressus
* Mounted fossilized skeleton of the Late Jurassic herbivorous dinosaur Othnielosaurus Ostrea
** †Ostrea inornata
* †Othnielia
* †Othnielosaurus
** †Othnielosaurus consors – type locality for species
* †Oxybeloceras
** †Oxybeloceras crassum
* †Oxytoma
** †Oxytoma nebrascana

## P

* A
* B
* C
* D
* E
* F
* G
* H
* I
* J
* K
* L
* M
* N
* O
* P
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* R
* S
* T
* U
* V
* W
* X
* Y
* Z
* Fossilized skeleton of the Late Cretaceous dome-headed dinosaur Pachycephalosaurus †Pachycephalosaurus
** †Pachycephalosaurus wyomingensis – type locality for species
* †Pachyrhizodus
* †Pachyteuthis
** †Pachyteuthis densus
* †Palaeoaster
** †Palaeoaster inquirenda
* †Palaeobatrachus
** †Palaeobatrachus occidentalis – type locality for species
* †Palaeocypraea
** †Palaeocypraea squyeri – type locality for species
* †Palaeosaniwa – type locality for genus
** †Palaeosaniwa canadensis – type locality for species
* †Paleoaster
** †Paleoaster inquirenda
* †Paleopsephurus
** †Paleopsephurus wilsoni
* †Paleorhinus
** †Paleorhinus parvus – type locality for species
* †Paliurus
** †Paliurus minimus
** †Paliurus zizyphoides – tentative report
* †Pantosaurus – type locality for genus
** †Pantosaurus striatus – type locality for species
* †Parachondroceras
** †Parachondroceras andrewsi
** †Parachondroceras filicostatum
* †Paracimexomys
** †Paracimexomys priscus
* †Paracredneria
** †Paracredneria cretacea – type locality for species
* †Paraderma – type locality for genus
** †Paraderma bogerti – type locality for species
* †Paradiscoglossus – type locality for genus
** †Paradiscoglossus americanus – type locality for species
* †Paralbula
** †Paralbula casei
* †Paramacellodus
** †Paramacellodus keebleri
* †Paranymphaea
** †Paranymphaea hastata
* †Parasaniwa – type locality for genus
** †Parasaniwa wyomingensis – type locality for species
* †Parastomechinus
** †Parastomechinus brightoni
* Life restoration of the Late Triassic phytosaur Parasuchus †Parasuchus
** †Parasuchus bransoni – type locality for species
* †Paressonodon
** †Paressonodon nelsoni
* †Pariguana – type locality for genus
** †Pariguana lancensis – type locality for species
* †Parikimys
** †Parikimys carpenteri
* †Parmicorbula
** †Parmicorbula bisulcata
* †Paronychodon
** †Paronychodon lacustris – type locality for species
* †Parvodus
* †Paurodon – type locality for genus
** †Paurodon valens – type locality for species
* †Pecopteris
** †Pecopteris borealis
** †Pecopteris Geyleriana
* Pecten
** †Pecten nebrascensis
* Micrograph of a fossilized tooth of the Late Cretaceous troodontid Pectinodon †Pectinodon – type locality for genus
** †Pectinodon bakkeri – type locality for species
* †Pediomys
** †Pediomys elegans – type locality for species
* †Pentacrinus
* †Permophorus
** †Permophorus triassicus – type locality for species
* Persea – report made of unidentified related form or using admittedly obsolete nomenclature
** †Persea hayana
* †Petalolepis – tentative report
** †Petalolepis fibrillatus
* †Phlycticrioceras
** †Phlycticrioceras trinodosus
* †Phoenicites – or unidentified comparable form
* Fossilized shell of the Early Triassic-Pliocene marine bivalve Pholadomya Pholadomya
** †Pholadomya inaequiplicata
** †Pholadomya kingi
* †Phragmites
** †Phragmites falcata
* †Phyllites
** †Phyllites crassipes
** †Phyllites cretaceous
** †Phyllites dentata
** †Phyllites ficifolius
** †Phyllites grandifolius-cretaceous
* Phyllodus
** †Phyllodus toliapicus
* A live individual of Physa marmorata Physa – or unidentified comparable form
* †Piceoerpeton
** †Piceoerpeton naylori
* Pinna
** †Pinna kingi
* Pinus
** †Pinus susquaensis
* Pistacia
** †Pistacia eriensis
* †Pistia
** †Pistia corrugata
* Fossilized shell of the Late Cretaceous ammonoid cephalopod Placenticeras †Placenticeras
** †Placenticeras intercalare
** †Placenticeras meeki
** †Placenticeras pseudoplacenta
* †Plagiostoma
** †Plagiostoma occidentalis
* Planorbis
* †Plastomenus
* †Platacodon – type locality for genus
** †Platacodon nanus – type locality for species
* †Platanites
** †Platanites marginata
* †Platanophyllum
** †Platanophyllum montanum
** †Platanophyllum platanoides
* Platanus
** †Platanus primaeva
* Life restoration of the Late Cretaceous mosasaur Platecarpus †Platecarpus
** †Platecarpus brachycephalus
** †Platecarpus tympaniticus
* †Platymya
** †Platymya rockymontana
* †Platypterygius
** †Platypterygius americanus – type locality for species
* †Plesiacanthoceras
** †Plesiacanthoceras bellsanum – or unidentified comparable form
** †Plesiacanthoceras wyomingense
* †Plesiobaena
** †Plesiobaena antiqua
* Life restoration of the Late Cretaceous plesiosaur Plesiopleurodon †Plesiopleurodon – type locality for genus
** †Plesiopleurodon wellesi – type locality for species
* †Plesiosaurus
** †Plesiosaurus shirleyensis – type locality for species
* †Pleuromya
** †Pleuromya haydeniana – type locality for species
** †Pleuromya subcompressa
* †Plicatolamna
** †Plicatolamna arcuata
* Plicatula
* Polinices
** †Polinices concinna – or unidentified related form
* †Polyacrodus
** †Polyacrodus parvidens – or unidentified comparable form
* †Polycotylus
* Restoration of the Late Triassic crocodile relative Poposaurus with an anachronistic human to scale †Poposaurus – type locality for genus
** †Poposaurus gracilis – type locality for species
* Populus
** †Populus aspens
** †Populus aspensis – type locality for species
* †Porosoma
** †Porosoma reesidei – type locality for species
* †Portheus
* †Postligata
** †Postligata crenata
* †Potamoceratodus
* †Potamornis – type locality for genus
** †Potamornis skutchi – type locality for species
* †Powellia – type locality for genus
** †Powellia oblongata – type locality for species
* †Priacodon
** †Priacodon ferox – type locality for species
** †Priacodon grandaevus – type locality for species
** †Priacodon lulli – type locality for species
** †Priacodon robustus – type locality for species
* †Prionocyclus
** †Prionocyclus germari
** †Prionocyclus hyatti
** †Prionocyclus novimexicanus
* †Prodesmodon – type locality for genus
** †Prodesmodon copei – type locality for species
* †Prodiplocynodon – type locality for genus
** †Prodiplocynodon langi – type locality for species
* †Promyalina
** †Promyalina putiatinensis
** †Promyalina spathi
* †Pronoella
** †Pronoella cinnabarensis
** †Pronoella iddingsi – or unidentified comparable form
** †Pronoella uintahensis
* †Prorokia
** †Prorokia fontenellensis
* †Protalphadon
** †Protalphadon lulli – type locality for species
* †Protexanites
** †Protexanites bourgeoisianus
* †Protocardia
** †Protocardia rara
** †Protocardia schucherti – or unidentified comparable form
* †Protolambda
** †Protolambda florencae – type locality for species
** †Protolambda hatcheri
* †Protophyllocladus
** †Protophyllocladus subintegrifolius
* †Protophyllum
* †Protoplatyrhina
** †Protoplatyrhina renae
* Fossilized mandible of the Late Cretaceous-Paleocene mammal Protungulatum †Protungulatum – tentative report
* Prunus
** †Prunus aspensis – type locality for species
* †Psalodon
** †Psalodon fortis – type locality for species
** †Psalodon marshi – type locality for species
** †Psalodon potens – type locality for species
* †Pseudoctenis
** †Pseudoctenis AF013 – informal
* †Pseudodontaspis – type locality for genus
** †Pseudodontaspis herbsti – type locality for species
* †Pseudoperna
** †Pseudoperna congesta
* †Pteraichnus
** †Pteraichnus stokesi – type locality for species
* Life restoration of the Late Cretaceous pterosaur Pteranodon †Pteranodon
** †Pteranodon longiceps
* †Pteria
** †Pteria gastrodes
** †Pteria linguaeformis
** †Pteria linguiformis
** †Pteria lingulaeformis
** †Pteria ussurica – or unidentified comparable form
* †Pterodactylus
** †Pterodactylus montanus – type locality for species
* †Ptilotodon
** †Ptilotodon wilsoni
* †Ptychodous
* †Ptychotrygon
** †Ptychotrygon boothi – type locality for species
** †Ptychotrygon ellae – type locality for species
** †Ptychotrygon greybullensis – type locality for species

## Q

* A
* B
* C
* D
* E
* F
* G
* H
* I
* J
* K
* L
* M
* N
* O
* P
* Q
* R
* S
* T
* U
* V
* W
* X
* Y
* Z
* †Quenstedtia
** †Quenstedtia sublevis
** A living Quercus, or oak tree †Quenstedtia sublewis
* †Quercophyllum
** †Quercophyllum gardneri
** †Quercophyllum wyomingense – type locality for species
* Quercus
** †Quercus ellisiana
** †Quercus stantoni
** †Quercus stantonii
** †Quercus viburnifolia
* †Quereuxia
** †Quereuxia angulata

## R

* A
* B
* C
* D
* E
* F
* G
* H
* I
* J
* K
* L
* M
* N
* O
* P
* Q
* R
* S
* T
* U
* V
* W
* X
* Y
* Z
* †Raninella
* †Reesidella
* †Retinovena – type locality for genus
** †Retinovena fluvialis – type locality for species
* †Retispira
** †Retispira bittneri
* Rhabdocolpus – tentative report
* †Rhaeboceras
** †Rhaeboceras halli
** †Rhaeboceras subglobosum
* †Rhamnus
** Micrograph with magnified inset of a fossilized tooth of the Late Cretaceous theropod dinosaur Richardoestesia †Rhamnus hirsuta
** †Rhamnus minutus
* Rhinobatos
** †Rhinobatos casieri
* †Rhizocorallium
* †Rhynchosauroides – type locality for genus
** †Rhynchosauroides palmatus – type locality for species
* †Richardoestesia
** †Richardoestesia isosceles
* †Ropalonaria
** †Ropalonaria arachne
* Rostellaria – tentative report
* †Rotodactylus – or unidentified comparable form

## S

* A
* B
* C
* D
* E
* F
* G
* H
* I
* J
* K
* L
* M
* N
* O
* P
* Q
* R
* S
* T
* U
* V
* W
* X
* Y
* Z
* †Sabalites
** †Sabalites eocenica
** †Sabalites montana
* †Saccoloma – report made of unidentified related form or using admittedly obsolete nomenclature
** †Saccoloma gardneri
* †Saliciphyllum
** †Saliciphyllum wyomingensis
* A living Salix, or willow Salix
** †Salix cumberlandensis
** †Salix frontierensis
** †Salix lancensis
* †Salpichlaena
** †Salpichlaena AF003 – informal
* †Sapindopsis
** †Sapindopsis belviderensis
** †Sapindopsis magnifolia
** †Sapindopsis schultzi – type locality for species
** †Sapindopsis schultzii
** †Sapindopsis variabilis
* †Sarjeantopodus – type locality for genus
** †Sarjeantopodus semipalmatus – type locality for species
* Foliage of a living Sassafras tree Sassafras
** †Sassafras bradleyi – type locality for species
** †Sassafras bradleyii
** †Sassafras thermale
* †Saurexallopus – type locality for genus
** †Saurexallopus lovei – type locality for species
** †Saurexallopus zerbsti – type locality for species
* †Saurocephalus
* †Saurolophus
* †Sauropelta
** †Sauropelta edwardsorum
* Diagram illustrating the Early Cretaceous long-necked dinosaur Sauroposeidon with anachronistic humans to scale †Sauroposeidon
** †Sauroposeidon proteles
* †Saurornithoides – or unidentified comparable form
* †Saurornitholestes
* †Sauvagesia
** †Sauvagesia austinensis – or unidentified comparable form
* †Scapanorhynchus
** †Scapanorhynchus texanus
* †Scapherpeton
** †Scapherpeton tectum
* Fossilized shell of the Late Cretaceous ammonoid cephalopod Scaphites †Scaphites
** †Scaphites aquilaensis
** †Scaphites binneyi
** †Scaphites hippocrepis
** †Scaphites stantoni
** †Scaphites ventricosus
** †Scaphites whitfieldi
* †Scleropteris
** †Scleropteris distantifolia – type locality for species
** †Scleropteris rotundifolia – type locality for species
* †Scotiophryne
** †Scotiophryne pustulosa
* Scyliorhinus
** †Scyliorhinus tensleepensis – type locality for species
* †Selaginella
** †Selaginella falcata – tentative report
* †Semiungula – type locality for genus
** †Semiungula assymetrica – type locality for species
* Base of the trunk of a living Sequoia tree with a human to scale Sequoia
** †Sequoia cuneata
** †Sequoia dakotensis
** †Sequoia gracilia
** †Sequoia gracilis
** †Sequoia langsdorfii
** †Sequoia reichenbachi
** †Sequoia Reichenbachi
* †Serrifusus
** †Serrifusus dakotensis
* †Skolithos
* †Smilax
** †Smilax coloradensis – tentative report
* †Socognathus
** †Socognathus brachyodon – type locality for species
* †Sohlites
** †Sohlites spinosus
* †Sokophyllum – type locality for genus
** †Sokophyllum dentatum – type locality for species
* Modern specimen of the marine bivalve Solemya Solemya
** †Solemya bilix
** †Solemya obscura
* †Solenoceras
* †Solyma
* †Sparganium
** †Sparganium aspens
** †Sparganium aspensis – type locality for species
* Sphaerium – or unidentified comparable form
* †Sphenodiscus
** †Sphenodiscus lobatus – or unidentified comparable form
** †Sphenodiscus pleurisepta
* †Sphenolepidium
** †Sphenolepidium Kurrianum
** †Sphenolepidium parceramosum
* †Sphenopteris
** †Sphenopteris plurinervia
* †Spiroceras
** †Spiroceras orbignyi – or unidentified comparable form
* Fossilized tooth of the Late Cretaceous shark Squalicorax Squalicorax
** †Squalicorax kaupi
** †Squalicorax pristodontus
* †Squatirhina
** †Squatirhina americana – type locality for species
** †Squatirhina roessingi – type locality for species
* †Staphylea
** †Staphylea fremonti
** †Staphylea fremontii
* †Stegopelta – type locality for genus
** †Stegopelta landerensis – type locality for species
* Restoration of the Late Jurassic stegosaur Stegosaurus †Stegosaurus – type locality for genus
** †Stegosaurus affinis – type locality for species
** †Stegosaurus armatus – type locality for species
** †Stegosaurus longispinus – type locality for species
** †Stegosaurus stenops
** †Stegosaurus sulcatus – type locality for species
** †Stegosaurus ungulatus – type locality for species
* †Steinichnus
* †Stemmatoceras
** †Stemmatoceras albertense – or unidentified related form
* Sterculia
** †Sterculia mucronata
** †Sterculia towneri
* †Stokesosaurus – tentative report
** †Stokesosaurus clevelandi
* †Struthiomimus – or unidentified comparable form
* Restoration in multiple views of the Late Jurassic sauropod dinosaur Supersaurus with an anachronistic human to scale †Stygiochelys
* †Styxosaurus
** †Styxosaurus browni – type locality for species
* †Supersaurus
** †Supersaurus vivianae
* †Syncyclonema
** †Syncyclonema rigida
* †Synechodus
** †Synechodus turneri – type locality for species

## T

* A
* B
* C
* D
* E
* F
* G
* H
* I
* J
* K
* L
* M
* N
* O
* P
* Q
* R
* S
* T
* U
* V
* W
* X
* Y
* Z
* †Tancredia
** †Tancredia transversa
* Life restoration of the Late Jurassic theropod dinosaur Tanycolagreus †Tanycolagreus – type locality for genus
** †Tanycolagreus topwilsoni – type locality for species
* Tapeinidium
** Tapeinidium undulatum – tentative report
* †Tarrantoceras
** †Tarrantoceras exile – type locality for species
** †Tarrantoceras flexicostatum – type locality for species
** †Tarrantoceras sellardsi
* †Tatenectes
** †Tatenectes laramiensis – type locality for species
* †Tathiodon – type locality for genus
** †Tathiodon agilis – type locality for species
* †Telacodon
** †Telacodon laevis – type locality for species
* †Tenea
** †Tenea circularis
* Life restoration of the Early Cretaceous Iguanodon relative Tenontosaurus †Tenontosaurus
** †Tenontosaurus tilletti
* Teredo
* †Thalassinoides
* †Theatonius – type locality for genus
** †Theatonius lancensis – type locality for species
* †Theretairus – type locality for genus
** †Theretairus antiquus – type locality for species
* Life restoration of the Late Cretaceous herbivorous dinosaur Thescelosaurus †Thescelosaurus – type locality for genus
** †Thescelosaurus neglectus – type locality for species
* †Thescelus
** †Thescelus insiliens – type locality for species
* †Thoracosaurus – or unidentified comparable form
* Thracia
** †Thracia weedi
* Thyasira
* Illustration of a living Thyrsopteris tree fern †Thyrsopteris
** †Thyrsopteris brevifolia
** †Thyrsopteris brevipennis
** †Thyrsopteris crassinervis
** †Thyrsopteris dentifolia – type locality for species
** †Thyrsopteris elliptica
** †Thyrsopteris pecopteroides
** †Thyrsopteris pinnatifida
* †Tinodon – type locality for genus
** †Tinodon bellus – type locality for species
* †Torosaurus – type locality for genus
** †Torosaurus latus – type locality for species
* †Torotix – type locality for genus
** †Torotix clemensi – type locality for species
* Mounted fossilized skeleton of the Late Jurassic megalosaur Torvosaurus †Torvosaurus – type locality for genus
** †Torvosaurus tanneri – type locality for species
* †Trachodon
* †Trachyscaphites
** †Trachyscaphites redbirdensis
* †Trachytriton
** †Trachytriton vinculum
* †Tragodesmoceras
** †Tragodesmoceras carlilense
* †Trapa
** †Trapa microphylla
* Mounted fossilized skeleton of the Late Cretaceous horned dinosaur Triceratops †Triceratops – type locality for genus
** †Triceratops horridus – type locality for species
** †Triceratops ingens – type locality for species
** †Triceratops prorsus – type locality for species
** †Triceratops sulcatus – type locality for species
* †Trigonia
** †Trigonia americana
** †Trigonia elegantissima
** †Trigonia montanaensis
** †Trigonia quadrangularis
* †Trioracodon
** †Trioracodon bisulcus – type locality for species
* Fossilized skeleton of the Late Cretaceous tyrannosaur Tyrannosaurus Trochocyathus – tentative report
* †Trochodendroides
* †Troodon
** †Troodon formosus
* †Turgidodon
** †Turgidodon rhaister – type locality for species
** †Turgidodon russelli
* Typha
* †Tyrannosaurus – type locality for genus
** †Tyrannosaurus rex – type locality for species

## U

* A
* B
* C
* D
* E
* F
* G
* H
* I
* J
* K
* L
* M
* N
* O
* P
* Q
* R
* S
* T
* U
* V
* W
* X
* Y
* Z
* †Ulmiphyllum
** †Ulmiphyllum densinerve – type locality for species
* †Uluops – type locality for genus
** †Uluops uluops – type locality for species
* Unio
* †Unionites
** †Unionites fassaensis

## V

* A
* B
* C
* D
* E
* F
* G
* H
* I
* J
* K
* L
* M
* N
* O
* P
* Q
* R
* S
* T
* U
* V
* W
* X
* Y
* Z
* Vanikoro
** †Vanikoro ambigua
* †Vanikoropsis
** †Vanikoropsis nebrascensis
* †Vaugonia
** Leaves and fruit of a living Vitis, or grapevine †Vaugonia conradi
* †Veniella
** †Veniella mortoni
* †Viburnum
** †Viburnum marginatum
** †Viburnum montanum
** †Viburnum rotundifolium
* Vitis
** †"Vitis" stantoni
* Viviparus – or unidentified comparable form
* †Volutoderma

## W

* A
* B
* C
* D
* E
* F
* G
* H
* I
* J
* K
* L
* M
* N
* O
* P
* Q
* R
* S
* T
* U
* V
* W
* X
* Y
* Z
* †Weediaphyllum – type locality for genus
** †Weediaphyllum parkensis – type locality for species
* †Weichselia
** †Weichselia reticulata
* †Williamsonia – tentative report
** †Williamsonia phoenicopsoides – type locality for species
* †Woodwardia
** †Woodwardia crenata

## X

* A
* B
* C
* D
* E
* F
* G
* H
* I
* J
* K
* L
* M
* N
* O
* P
* Q
* R
* S
* T
* U
* V
* W
* X
* Y
* Z
* †Xenocephalites
* †Xenoxylon
* †Xiphactinus
** †Xiphactinus vetus

## Y

* A
* B
* C
* D
* E
* F
* G
* H
* I
* J
* K
* L
* M
* N
* O
* P
* Q
* R
* S
* T
* U
* V
* W
* X
* Y
* Z
* Yoldia
** †Yoldia scitula – or unidentified related form
** †Yoldia ventricosa

## Z

* A
* B
* C
* D
* E
* F
* G
* H
* I
* J
* K
* L
* M
* N
* O
* P
* Q
* R
* S
* T
* U
* V
* W
* X
* Y
* Z
* †Zamites
** †Zamites arcticus
** †Zamites borealis
** †Zamites brevipennis
* †Zapsalis – or unidentified comparable form
* †Zephyrosaurus – or unidentified comparable form
* †Zofiabaatar – type locality for genus
** †Zofiabaatar pulcher – type locality for species