Oarisma
O-boeta
O-bruneri
O-edwardsii
O-era
O-garita
O-nanus
O-poweshiek
Oaristes
Obatala
Obipteryx
Oboria(EXTINCT)
Oborocoleidae(EXTINCT)
Oborocoleus(EXTINCT)
Obricala
Obtectomera
Obtusitermes
Ocabaraja
Ocalea
Occasitermes
Occidozyga
Occiephelinus
Occithrissopidae(EXTINCT)
Oceanithermus
Oceanitidae(storm-petrels)
Oceanobacillus
Ocella
O-albata
O-diophthalma
O-monophthalma
Ochetellus
O-epinotalis
O-flavipes
O-glaber
O-itoi
O-punctatissimus
O-sororis
O-vinsoni
Ochetomyrmex
O-neopolitus
O-semipolitus
Ochlodes
O-agricola
O-batesi
O-ochracea
O-samenta
O-siva
O-subhyalina
O-sylvanoides
O-thibetana
O-venata
O-yuma
Ochnaceae(monophyly uncertain)
Ochotonidae(pikas, mouse hares, conies)
Ochridiola
Ochropyge
Ochtebiites(EXTINCT)
Ochteridae(velvety shore bugs)
Ochthebiina
Ochthebiinae
Ochthebiini
Ochthebius
O-(Asiobates)
O-(Ochthebius)
Ochtheosini
Ochtheosus
Ochthephilum
O-(Ababactus)
O-(Astenobium)
O-(Cryptobiella)
O-(Neobactus)
O-(Ochthephilum)
Ochthephilus
Ochus
Ochyroceratidae
Ocnotelus
Ocoidae
Octavius
Octineon lindahli(Carpenter) Fowler 1894
Octineon suecicumCarlgren 1940
Octineonidae
Octodesmus
Octomeros
Octomicrellus
Octomicrites
Octomicrus
Octopicolidae
OctopodaLeach, 1818
OctopodidaeOrbigny, 1839
OctopodiformesBerthold and Engeser, 1987(vampire squid and octopods)
OctopoteuthidaeBerry 1912
OctopoteuthisRuppell 1844
O-danae
O-deletronYoung, 1972
O-indica
O-megaptera
O-neilseni
O-rugosa
O-sicula
Octopus (sensu strictu)Cuvier, 1797*
Octostruma
O-balzani
O-batesi
O-betschi
O-iheringi
O-impressa
O-inca
O-petiolata
O-rugifera
O-rugiferoides
O-stenognatha
O-stenoscapa
O-wheeleri
Octotrocha
Octozethodes
Octozethus
Oculicosa
Oculina
Oculinidae
Oculininae
Oculolabrus
Ocyale
Ocyalus latirostris(Band-tailed Oropendola)
Ocyba
Ocybadistes
O-ardea
O-flavovittatus
O-hypomeloma
O-papua
O-walkeri
O-zelda
Ocychinus
Ocyllus
Ocymyrmex
O-afradu
Ocyolinus
Ocyota
O-dubia
O-fortepunctata
Ocyplanus
Ocypus
O-(Angulephallus)
O-(Matidus)
O-(Ocypus)
O-(Pseudocypus)
Ocys
OcythoidaeGray 1849
Ocyusa
Ocyustiba
Odacanthini
Odina
O-chrysomelaena
O-decoratus
O-hieroglyphica
Odinidae
Odocoileus(mule deer and white-tailed deer)
O-hemionus(mule deer)
O-virginianus(white-tailed deer)
Odoichoerus(EXTINCT)
Odonata(dragonflies and damselflies)
Odontalgini
Odontalgus
Odontellidae
Odonticoscapus
Odontiinae
Odontobuthus
Odontoceridae
Odontoceti(toothed whales, dolphins, porpoises) (monophyly uncertain)
Odontoconnus
Odontodactylidae
Odontolinus
Odontomachus
O-chelifer
Odontomantis
O-brachyptera
O-buehleri
O-chayuensis
O-euphrosyne
O-foveafrons
O-hainana
O-laticollis
O-longipennis
O-micans
O-montana
O-monticola
O-nigrimarginalis
O-parva
O-planiceps
O-rhyssa
O-xizangensis
Odontophoridae(New World Quail)
Odontophorus(Wood Quail)
O-atrifrons(Black-fronted Wood Quail)
O-balliviani(Stripe-faced Wood Quail)
O-capueira(Spot-winged Wood Quail)
O-columbianus(Venezuelan Wood Quail)
O-dialeucos(Tacarcuna Wood Quail)
O-erythrops(Rufous-fronted Wood Quail)
O-gujanensis(Marbled Wood Quail)
O-guttatus(Spotted Wood Quail)
O-hyperythrus(Chestnut Wood Quail)
O-leucolaemus(Black-breasted Wood Quail)
O-melanonotus(Dark-backed Wood Quail)
O-melanotis(Black-eared Wood Quail)
O-speciosus(Rufous-breasted Wood Quail)
O-stellatus(Starred Wood Quail)
O-strophium(Gorgeted Wood Quail)
Odontoponera transversa
Odontoptilum
O-abbreviata
O-angulata
O-corria
O-helias
O-pygela
Odontopygidae
Odontotermes
Odontoxenus
Odonturus
Oechydrus
Oecidiophilus
Oecobiidae
Oecomys(bicolored rice rats)
Oeconescidae
Oecophoridae(concealer moths) (monophyly uncertain)
Oecophylla(weaver ants)
O-atavina(EXTINCT)
O-bartoniana(EXTINCT)
O-brischkei(EXTINCT)
O-crassinoda(EXTINCT)
O-leakeyi(EXTINCT)
O-longinoda(African weaver ant)
O-megarche(EXTINCT)
O-obesa(EXTINCT)
O-perdita(EXTINCT)
O-praeclara(EXTINCT)
O-sicula(EXTINCT)
O-smaragdina(Asian-Australian weaver ant)
O-superba(EXTINCT)
Oedemeridae(false blister beetles)
Oedichirus
O-(Oedichiranus)
O-(Oedichirus)
Oedipina
Oedipodiaceae(incertae sedis)
Oedipodinae
Oedodactylus
OegopsidaOrbigny, 1845
Oemopteryx
Oeneis
O-actaeoides
O-aktashi
O-alberta
O-alpina
O-ammon
O-bore
O-brunhilda
O-buddha
O-chryxus
O-diluta
O-elwesi
O-fulla
O-glacialis
O-hora
O-ivallda
O-jutta
O-lederi
O-macounii
O-magna
O-melissa
O-mulla
O-nanna
O-nevadensis
O-norna
O-oeno
O-pansa
O-polixenes
O-rosovi
O-sculda
O-tarpeia
O-taygete
O-uhleri
O-urda
Oenococcus
Oenomys
Oenosandridae
Oeonus
O-edlichi
O-egma
O-pyste
Oeophronistus
Oerane
Oerskovia
Oesia disjuncta(EXTINCT) (Middle Cambrian) (incertae sedis)
Oestomantis bacillaris
Oestridae
Oestroidea
Ogcocephalidae(Batfishes)
Ogcocephalus
Ogmoceridius
Ogmocerodes
Ogmoceropsis
Ogmocerus
Ogmophora
Ogulnius
Ogygioses caliginosa
Ogygioses eurata
Ogygioses issikii
Ogygioses luangensis
Ohleriella(incertae sedis)
Oiceoptoma
Oiclus
Oideprosoma
Oileides
O-amazonensis
O-azines
O-fenestratus
O-vulpinus
Oioceros(EXTINCT)
Oithonidae
Okapia johnstoni(okapi)
Okavangotermes
Okeanobatidae
Okella
Okibacterium
Olacaceae(non-monophyletic)
Old World
Old World
Old World barbets
Old World Justicioids(non-monophyletic)
Old World
Old World
Old World deer
Olea(non-monophyletic)
Oleaceae(olive family)
Oleria
O-[n. sp. 1]
O-[n. sp. 2]
O-[n. sp. 3]
O-[n. sp. 4]
O-[n. sp. 5]
O-[n. sp. 6]
O-aegineta
O-aegle
O-agarista
O-alexina
O-amalda
O-antaxis
O-aquata
O-assimilis
O-astrea
O-athalina
O-attalia
O-baizana
O-bioculata
O-canilla
O-cyrene
O-deronda
O-derondina
O-enania
O-estella
O-fasciata
O-flora
O-fumata
O-gunilla
O-ilerdina
O-makrena
O-olerioides
O-onega
O-padilla
O-paula
O-phenomoe
O-quadrata
O-quintina
O-radina
O-rubescens
O-santineza
O-sexmaculata
O-similigena
O-synnova
O-tigilla
O-tremona
O-vicina
O-victorine
O-zea
O-zelica
Oleriina
Olethreutinae
Olethreutini
Oliera argentinana
Oligella
Oligembia
Oligocharina
Oligodonta(EXTINCT)
Oligodraninae
Oligokalotermes fischeri(EXTINCT) (Lower Oligocene of France)
Oligomantis
O-hyalina
O-mentaweiana
O-orientalis
Oligomyrmex
O-aborensis
Oligoneuriidae
Oligonicella
O-bolliana
O-brunneri
O-punctulata
O-scudderi
O-striolata
O-tessellata
Oligonicinae
Oligonicini
Oligonotus
Oligonyx
O-bicornis
O-bidens
O-dohrnianus
O-insularis
O-maya
Oligoria
Oligoryzomys
Oligosemia(EXTINCT)0(incertae sedis)
Oligota
Oligotergus
Oligotoma(Oligotomidae)
Oligotyphlopsis
Oligusa
Oliniaceae
Olisthaerinae
Ollicola
Ololygon
Olonbulukia(EXTINCT)
Olophrinus
Olophrum
Olpidium brassicae
Olsenella
Oltacola
Olympicomys(EXTINCT) (incertae sedis)
Olyras
O-crathis
O-insignis
O-theon
Omaliinae
Omaliinae group
Omaliini
Omaliomimus
Omaliopsis
Omalium
Omalodini
Omalonomus
Omalorphanus
Omalosoma
Omalosoma series(=Trichosternus series) (monophyly uncertain)
Omaniidae
Omethes
Omethidae(false soldier beetles, false firefly beetles)
Omicrini
Omicrogiton
Omicrus
Omikronpapillomavirus
Omma
O-aberratum(EXTINCT)
O-altajense(EXTINCT)
O-antennatum(EXTINCT)
O-avus(EXTINCT)
O-brevipes(EXTINCT)
O-gobiense(EXTINCT)
O-jurassicum(EXTINCT)
O-liassicum(EXTINCT)
O-mastersi
O-pilosum(EXTINCT)
O-rutherfordi
O-sagitta
O-sibiricum(EXTINCT)
O-stanleyi
O-zitteli(EXTINCT)
Ommastrephes
OmmastrephidaeSteenstrup 1857
OmmastrephinaePosselt 1891
Ommatidae
Ommatolampinae
Ommatotriton
Ommexechidae
Omniops
Omobathus
Omoglymmiina
Omoglymmius
O-(Boreoglymmius)
O-(Caeconavitia)
O-(Carinoglymmius)
O-(Hemiglymmius)
O-(Indoglymmius)
O-(Laminoglymmius)
O-(Navitia)
O-(Nitiglymmius)
O-(Omoglymmius s. str.)
O-(Orthoglymmius)
O-(Pyxiglymmius)
O-actae
O-africanus
O-alticola
O-americanus
O-amplus
O-aristeus
O-armatus
O-asetatus
O-astraea
O-auratus
O-batchianus
O-bicarinatus
O-biroi
O-bituberculatus
O-bouchardi
O-brendelli
O-bucculatus
O-caelatus
O-capito
O-carinatus
O-cavea
O-cavifrons
O-cheesmanae
O-classicus
O-coelebs
O-consors
O-continuus
O-coomani
O-crassicornis
O-crassiusculus
O-craticulus
O-crenatus
O-cristatus
O-cupedoides
O-data
O-denticulatus
O-duplex
O-emdomani
O-ephemeris
O-evasus
O-feae
O-ferrugatus
O-follis
O-fraudulentus
O-fringillus
O-fulgens
O-germaini
O-germari
O-gorgo
O-gracilicornis
O-greensladei
O-gressitti
O-gurneyi
O-hamatus
O-hemipunctatus
O-hesperus(incertae sedis)
O-hexagonus
O-hiekei
O-hornabrooki
O-humeralis
O-ichthyocephalus
O-impletus
O-imugani
O-inaequalis
O-ineditus
O-inermis
O-insularis
O-intrusus
O-iridescens
O-javanicus
O-krikkeni
O-largus
O-laticeps
O-lederi(incertae sedis)
O-lentus
O-lewisi
O-lindrothi
O-lineatus
O-longiceps
O-lustrans
O-malabaricus
O-malaicus
O-manni
O-massa
O-microtis
O-modicus
O-modiglianii
O-monteithi
O-morditus
O-multicarinatus0(incertae sedis)
O-mycteroides
O-nasalis
O-nemoralis
O-nicobarensis
O-oberthueri
O-occultus
O-oceanicus
O-offafinus
O-okei
O-opacus0(incertae sedis)
O-opticus
O-oroensis
O-patens
O-peckorum
O-pectoralis
O-philippensis
O-pilosus
O-planiceps
O-politus
O-princeps
O-pulvinatus
O-puncticornis
O-quadraticollis
O-quadruplex
O-regius
O-renutus
O-repetitus
O-rimatus
O-rugosus
O-rusticus
O-sabah
O-sakuraii
O-scopulinus
O-sectatus
O-sedlaceki
O-semioculatus
O-semperi
O-seriatus
O-solitarius
O-strabus
O-stylatus
O-subcaviceps
O-sulcicollis
O-summissus
O-sus
O-tabulatus
O-thoracicus
O-tolai
O-toxopei
O-trepidus
O-trisinuatus
O-vadosus
O-vicinus
O-viduus
O-wallacei
O-wittmeri
O-zimmermani
Omologlusa
Omomantis
O-sigma
O-tigrina
O-zebrata
Omophronini
Omoplandria
Omotimellus
Omotimiotes
Omotimus
Omotropis(1 species)
Omphalotaceae
Onagraceae(evening primrose family)
Onagreae
Oncaeidae
Onchnesoma(incertae sedis)
Oncobrya decepta(EXTINCT)
Oncopaederus
Oncoparia
Oncopera
O-alboguttata
O-alpina
O-brachyphylla
O-brunneata
O-epargyra
O-fasciculatus
O-intricata
O-intricoides
O-mitocera
O-parva
O-rufobrunnea
O-tindalei
Oncopoduridae
Oncotheca
Oncylocotis
Ondinea purpurea
One Lipped Corolla Lineage
Oneila
Oneirodes
Oneirodidae(Dreamers)
Onenses
O-hyalophora
O-kelso
Onespa nubis
Oniromyiinae
Oniscidea
Oniscigastridae
Onkotermes
Onocolus
Onomastus
Onophas
O-chlorocephala
O-columbaria
O-watsoni
Onryza
O-maga
O-meiktila
O-siamica
Ontholestes
Onthophilinae(non-monophyletic)
Onthophilus
Onychiuridae
Onychiurinae
Onychodactylus fischeri
Onychodactylus japonicus
Onychodontiformes(EXTINCT) (incertae sedis)
Onychognathia
Onychojapyx schmidti(EXTINCT) (Paleocene - Pliocene of Arizona, USA) (incertae sedis)
Onycholobus
Onychomyrmex
O-doddi
O-hedleyi
O-mjobergi
Onychophora(velvet worms)
Onychoplax
OnychoteuthidaeGray, 1849
OnychoteuthisLichtenstein, 1818
O-banksiiLeach, 1817
O-borealijaponicaOkada, 1927
O-compacta(Berry, 1913)
O-meridiopacificaRancurel & Okutani, 1990
Onygenales
OnykiaLesueur, 1821
O-aequatorialis(Thiele 1920)
O-carriboeaLesueur, 1821
O-ingens(Smith, 1881)
O-knipovitchi(Filippova, 1972)
O-loennbergii(Ishikawa and Wakiya 1914)
O-robsoni(Adam, 1962)
O-robusta(Verrill, 1876)
Oocyclus
Oodini
Oodinkosa
Oomtelecopon
Oomycetes
Oonopidae
Oosternum
Ootitan(EXTINCT)
Opadosister
Opalines
Operculea
Ophelius
Ophiacodontidae(EXTINCT)
Ophichthidae
Ophidiiformes(pearlfishes and relatives)
Ophiobotrys zenkeri
Ophiodiscus
O-annulatusR. Hertwig 1882
O-sulcatusR. Hertwig 1882
Ophiodrominae
Ophiodromini
Ophiodromus
Ophioglossa
Ophioglossales
Ophiomedon
Ophionthus
Ophioomma
Ophiotermes
Ophiovirus
Ophitodum
Ophiuroidea(brittle-stars and basket-stars)
Ophonichius
Ophryomedon
Ophthalmocyclus
Ophthalmoniphetodes
Ophthalmopone berthoudi
Ophthalmopsocus
Opiinae
Opiliaceae
Opilioacariformes
Opiliones(harvestmen, daddy-longlegs)
Opisthacanthus
Opisthiini
Opisthius richardsoni
Opisthocheiridae
Opisthocomiformes(Hoatzin)
Opisthophthalmus
Opisthoplatia
Opisthopsis
O-diadematus
O-haddoni
O-halmaherae
O-jocosus
O-lienosus
O-linnaei
O-major
O-manni
O-maurus
O-panops
O-pictus
O-respiciens
O-rufithorax
Opisthosemus
Opisthosphaera
OpisthoteuthidaeVerrill, 1896
OpisthoteuthisVerrill, 1883
O-agassiziiVerrill, 1883
O-albatrossi(Sasaki, 1920)
O-bruuniVoss, 1982
O-californianaBerry, 1949
O-calypsoVillanueva, Collins, Sanchez and Voss 2002
O-chathamensisO'Shea, 1999
O-depressaIjima & Ikeda, 1895
O-extensaThiele, 1915
O-grimaldiiJoubin, 1903
O-hardyiVillanueva, Collins, Sanchez and Voss 2002
O-massyae(Grimpe, 1920)
O-medusoidesThiele, 1915
O-meroO'Shea, 1999
O-persephoneBerry, 1918
O-philipiiOommen, 1976
O-plutoBerry, 1918
O-robsoniO'Shea, 1999
Opisthothelae
Opisthothylax
Opithes
Opitutus
Opluridae
Opomyzidae
Opomyzoidea
Opoptera
O-[n. sp.]
O-aorsa
O-arsippe
O-fruhstorferi
O-sulcius
O-syme
Opostega
Opostegidae(white eye-cap moths)
Oposteginae
Opostegoides
Opostegoidinae
Opsiphanes
O-bogotanus
O-boisduvalii
O-camena
O-cassiae
O-cassina
O-invirae
O-mutatus
O-quiteria
O-sallei
O-tamarindi
O-zelotes
Ora
Oractis
O-diomedeaeMc Murrich [sic] 1893
Orangemeryx(EXTINCT)
Orazethus
Orbiculariae(orb weavers, cobweb spiders, widows, etc.)
Orbiliomycetes
Orbivirus
Orchesellinae
Orchidaceae
Orchonoceros(EXTINCT)
Orchymontia
Orchymontiinae
Orconectes
O-(Billecambarus)
O-(Buannulifictus)
OB-hobbsi
OB-meeki brevis
OB-meeki meeki
OB-palmeri creolanus
OB-palmeri longimanus
OB-palmeri palmeri
O-(Crockerinus)
OC-bisectus
OC-erichsonianus
OC-eupunctus
OC-illinoiensis
OC-jeffersoni
OC-marchandi
OC-obscurus
OC-propinquus
OC-rafinesquei
OC-sanbornii erismophorous
OC-sanbornii sanbornii
OC-shoupi
OC-stannardi
OC-tricuspis
OC-virginiensis
O-(Faxonius)
OF-indianensis
OF-limosus
OF-wrighti
O-(Gremicambarus)
OG-alabamensis
OG-causeyi
OG-chickasawae
OG-compressus
OG-cooperi
OG-etnieri
OG-holti
OG-immunis
OG-mississippiensis
OG-nais
OG-rhoadesi
OG-validus
OG-virilis
O-(Hespericambarus)
OH-blacki
OH-deanae
OH-difficilis
OH-hathawayi
OH-maletae
OH-perfectus
O-(Orconectes)
OO-australis australis
OO-australis packardi
OO-incomptus
OO-inermis inermis
OO-inermis testii
OO-pagei
OO-pellucidus
OO-sheltae
O-(Procericambarus)
OP-acares
OP-barrenensis
OP-durelli
OP-forceps
OP-hylas
OP-leptogonopodus
OP-longidigitus
OP-luteus
OP-macrus
OP-medius
OP-menae
OP-mirus
OP-nana
OP-neglectus chaenodactylus
OP-neglectus neglectus
OP-ozarkae
OP-peruncus
OP-placidus
OP-punctimanus
OP-putnami
OP-quadruncus
OP-rusticus
OP-saxatilis
OP-spinosus
OP-transfuga
OP-williamsi
O-(Rhoadesius)
OR-kentuckiensis
OR-sloanii
O-(Tragulicambarus)
O-(Trisellescens)
O-alabamensis
O-chickasawae
O-cooperi
O-etnieri
O-holti
O-immunis
O-mississippiensis
O-rhoadesi
O-validus
Oreamnos americanus(Rocky Mountain goat)
Orectochilus
Orectognathus
O-alligator
Orectogyrus
Orectoscelis(non-monophyletic)
O-attenuatusDégallier & Caterino
O-aurolepidusCaterino
O-blackburniDégallier & Caterino
O-circularisCaterino
O-duboulaii(Westwood)
O-dumogaeCaterino
O-halmaheraeDégallier & Caterino
O-howdeniDégallier & Caterino
O-humeralisLewis
O-kovarikiDégallier & Caterino
O-marginicollisDégallier & Caterino
O-obliquusCaterino
O-okeiDégallier & Caterino
O-peninsularisDégallier & Caterino
O-punctatusCaterino
O-shihoaeNishikawa
O-ubirrDégallier & Caterino
O-westwoodiDégallier & Caterino
Oreinotyphlus
Oreisplanus
O-munionga
O-perornata
Oreixenica
O-correae
O-kershawi
O-lathoniella
O-latialis
O-orichora
O-ptunarra
Orenia
Oreocyon
Oreoica(crested bellbird)
Oreomicrus
Oreonagor(EXTINCT)
Oreopaederus
Oreophasis derbianus(Horned Guan)
Oreophryne
Oreophrynella
Oreopsocus
Oreortyx pictus(Mountain Quail)
Oreotragus oreotragus(klipspringer)
Oresigenus
Oressinoma
O-sorata
O-typhla
Oreuryalea
Oreusa
Orgilinae
Oribatida (part A)
Oribatida (part B)
Oribazus
O-catenulatus
O-quinquiestriatus
Oriencapritermes
Oriens
O-alfurus
O-augustulus
O-concinna
O-gola
O-goloides
O-paragola
Oriensubulitermes
Orientamaurops
Orientotermes
Origmatogonidae
Orinentomon
Orinocosa
Orinoma
O-alba
O-damaris
Oriolidae(Old World orioles)
Oritocatopini
Oritocatops
Orlandia
Ormomantis
O-indica
O-yunnanensis
Ormyridae
Ornatiblatta
Ornipholidotos
O-aurivilliusi
O-bakotae
O-bitjeensis
O-camerunensis
O-congoensis
O-emarginata
O-etoumbi
O-gabonensis
O-issia
O-jacksoni
O-katangae
O-kelle
O-kirbyi
O-larseni
O-latimargo
O-likouala
O-muhata
O-nguru
O-nigeriae
O-ntebi
O-onitshae
O-overlaeti
O-paradoxa
O-perfragilis
O-peucetia
O-sylpha
O-tanganyikae
O-teroensis
O-tiassale
O-tirza
O-ugandae
Ornithinicoccus
Ornithinimicrobium
Ornithischia(EXTINCT) (bird-hipped plant-eating dinosaurs)
Ornithobacterium
Ornithogaloideae
Ornitholestes(EXTINCT)
Ornithomimidae(EXTINCT) (ostrich-like dinosaurs)
Ornithopoda(EXTINCT) (duckbills, Iguanodon, heterodontosaurids, hypsilophodontids, and relatives)
Ornithorhynchidae
Ornithorhynchus anatinus(platypus)
Ornithosuchidae(EXTINCT)
Ornithoteuthis
Oroaetus
Orobanchaceae(broomrape family)
Orobanus
Orobothriurus
Orobrassolis
Orochares
Oroekklina
Oromantis
Oromerycidae(EXTINCT)
Orontieae
Oroperla
Orophila
O-cardases
O-diotima
Oropodes
Oropus
Orostygia
Oroussetiella
Oroya aurora
Orphe
O-gerasa
O-vatinius
Orphilus
Orphnebius
Orropygia
Orses
O-cynisca
O-itea
Orsodacne
Orsodacnidae
Orsolobidae
Orsotriaena
O-jopas
O-medus
Ortalis(Chachalacas)
O-araucuan(East Brazilian Chachalaca)
O-canicollis(Chaco Chachalaca)
O-cinereiceps(Grey-headed Chachalaca)
O-columbiana(Colombian Chachalaca)
O-erythroptera(Rufous-headed Chachalaca)
O-garrula(Chestnut-winged Chachalaca)
O-guttata(Speckled Chachalaca)
O-leucogastra(White-bellied Chachalaca)
O-motmot(Little Chachalaca)
O-poliocephala(West Mexican Chachalaca)
O-ruficauda(Rufous-vented Chachalaca)
O-ruficeps(Chestnut-headed Chachalaca)
O-squamata(Scaled Chachalaca)
O-superciliaris(Buff-browed Chachalaca)
O-vetula(Plain Chachalaca)
O-wagleri(Rufous-bellied Chachalaca)
Ortelytron(EXTINCT)
Ortheziidae(ensign coccids)
Orthidus
Orthoceratoidea
Orthochirus
Orthocosa
Orthodera
O-australiana
O-burmeisteri
O-gracilis
O-gunnii
O-insularis
O-ministralis
O-novaezealandiae
O-rubrocoxata
Orthoderella
O-deluchii
O-ornata
Orthoderina
O-fergusoniana
O-straminea
Orthoderinae
Orthogastropoda
Orthognathotermes
Orthogoniini
Orthomus
Orthomyxoviridae
Orthonectida
Orthonychidae(logrunners)
Orthophyia longa(EXTINCT)0(incertae sedis)
Orthopoxvirus
Orthopsyllidae
Orthoptera(grasshoppers, crickets, katydids, etc.)
Orthoreovirus
Orthos
O-gabina
O-lycortas
O-orthos
O-potesta
O-trinka
Orthosterni
Orthotermes
Orthotrichales
Ortilia
O-dicoma
O-gentina
O-ithra
O-liriope
O-orthia
O-orticas
O-polinella
O-sejona
O-velica
Orus
O-(Leucorus)
O-(Orus)
O-(Pycnorus)
Orussoidea
Orycteropus afer
Oryotus
Oryssomma
Oryx dammah(scimitar-horned oryx)
Oryx gazella(gemsbok)
Oryx leucoryx(Arabian oryx)
Oryzavirus
Oryzomyalia
Oryzomyini(rice rats, spiny mice, marsh rats)
Oryzomys(rice rats) (non-monophyletic)
Oryzorictes(rice tenrecs)
O-hova(Hova rice tenrec)
O-talpoides(molelike rice tenrec)
O-tetradactylus(four-toed rice tenrec)
Oryzorictinae(monophyly uncertain)
Orzolina
Osbornoceros(EXTINCT)
Oscadytes
Oschinotherium(EXTINCT)
Oscillatoria
Oscillochloris
Oscillospira
Oscines(Complex voice box, worldwide distribution)
Osericta
Osirini
Osmanthus(non-monophyletic)
Osmelia
Osmeridae
Osmeroidea
Osmeroidei
Osmodes
O-adon
O-adonia
O-adonides
O-adosus
O-banghaasii
O-costatus
O-distincta
O-hollandi
O-laronia
O-lindseyi
O-lux
O-maesseni
O-minchini
O-omar
O-thora
Osmundaceae
Osmylidae0(incertae sedis)
Osoriellus
Osoriinae
Osoriini
Osoriocanthus
Osoriopsis
Osorius
Osornophryne
Osphantes
Osrhoes coronta
Ostanes
Ostariophysicarps and minnows, suckers, piranhas, eletric eels, catfishes
Osteichthyes
Osteocephalus
Osteoglossidae
Osteoglossiformes
Osteoglossomorphabony tongues, butterfly fish, mooneye, featherbacks, elephant fishes
Osteolepimorpha(EXTINCT)
Osteopilus
Osteostraci(EXTINCT)
Ostraciidae
Ostracoda(seed shrimps)
Ostrocerca
Ostropales
Ostropomycetidae
Otagonia
Otariidae(sea lions, eared seals, fur seals)
Other "Maevia"
Other New World Acantheae
Othiini
Othius
Otididae(Bustards)
Otira
Otis tarda(Great Bustard)
Otitidae
Otlestidae(EXTINCT)
Otolemur crassicaudatus
Otolemur garnettii
Otomantis
O-aurita
O-capirica
O-casaica
O-rendalli
O-scutigera
Otomyine group
Otomys
Otonyctomys
Otophryne
Otophysi
Otostephanos
Otostigminae
Ototylomys
Ototyphlonemertidae(monophyly uncertain)
Ottoceros(EXTINCT)
Otus(Scops Owls)
O-alfredi(Flores Scops Owl)
O-alius(Nicobar Scops Owl)
O-angelinae(Javan Scops Owl)
O-bakkamoena(Collared Scops Owl)
O-balli(Andaman Scops Owl)
O-beccarii(Biak Scops Owl)
O-brookii(Rajah Scops Owl)
O-brucei(Pallid Scops Owl)
O-collari(Sangihe Scops Owl)
O-elegans(Ryukyu Scops Owl)
O-fuliginosus(Palawan Scops Owl)
O-hartlaubi(Sao Tome Scops Owl)
O-icterorhynchus(Sandy Scops Owl)
O-insularis(Seychelles Scops Owl)
O-ireneae(Sokoke Scops Owl)
O-longicornis(Luzon Scops Owl)
O-madagascariensis(Torotoroka Scops Owl)
O-magicus(Moluccan Scops Owl)
O-manadensis(Sulawesi Scops Owl)
O-mantananensis(Mantanani Scops Owl)
O-mayottensis(Mayotte Scops Owl)
O-megalotis(Philippine Scops Owl)
O-mentawi(Mentawai Scops Owl)
O-mindorensis(Mindoro Scops Owl)
O-mirus(Mindanao Scops Owl)
O-moheliensis(Moheli Scops Owl)
O-pauliani(Karthala Scops Owl)
O-pembaensis(Pemba Scops Owl)
O-rufescens(Reddish Scops Owl)
O-rutilus(Rainforest Scops Owl)
O-sagittatus(White-fronted Scops Owl)
O-scops(Eurasian Scops Owl)
O-senegalensis(African Scops Owl)
O-siaoensis(Siau Scops Owl)
O-silvicola(Wallace's Scops Owl)
O-spilocephalus(Mountain Scops Owl)
O-sulaensis(Sula Scops Owl )
O-sunia(Oriental Scops Owl)
O-thilohoffmanni(Serendib Scops Owl)
O-umbra(Simeulue Scops Owl)
Ouachitychus
Oudaimosister
Oulactis
Oulactis Danae[sic] Duchassaing and Michelotti 1860
Oulactis californicaMc Murrich [sic] 1893
Oulactis conquilegaDuchassaing and Michelotti 1860
Oulactis plicataHutton 1878
Oulactis radiataDuchassaing and Michelotti 1860
Oulangia
Ouleus
O-accedens
O-bubaris
O-calavius
O-candidus
O-cyrna
O-dilla
O-fatinitza
O-fridericus
O-juxta
O-narycus
O-negrus
Ouloglene
Oulopteryx
Ourebia ourebi(oribi)
Ourmiavirus
Ourocnemis
O-archytas
O-boulleti
Ousipalia
Ousipaliaglossa
Outachyusa
Ouzocerus(EXTINCT)
Ovambotermes
Overbeckia subclavata
Ovibos moschatus(muskox)
Oviparosiphidae(EXTINCT)
Oviraptorosauria(EXTINCT)
Ovis(sheep)
O-ammon(argali)
O-aries(mouflon, feral sheep)
O-canadensis(bighorn sheep)
O-dalli(dall sheep, Dall's sheep, Fannin's sheep, Stone's sheep)
O-nivicola(snow sheep)
O-vignei(urial)
Ovobathysciola
Ovocyrtusa
Oxacron(EXTINCT)
Oxaeinae
Oxalidaceae(wood sorrel family)
Oxalidales
Oxalophagus
Oxarthrius
O-(Baroxarthrius)
O-(Oxarthrius)
Oxelytrum
Oxeoschistus
O-cothon
O-cothonides
O-hilara
O-iphigenia
O-leucospilos
O-pronax
O-puerta
O-tauropolis
Oxobacter
Oxybessoglossa
Oxybleptes
Oxycanus
O-aedesima
O-aegrus
O-albostrigata
O-altenai
O-antipoda
O-armatus
O-atrox
O-aurifex
O-australis
O-ballux
O-barnardi
O-beltista
O-buluwandji
O-byrsa
O-carus
O-determinate
O-diakonoffi
O-dirempta
O-discipennis
O-dives
O-eos
O-fuliginosa
O-gelidus
O-glauerti
O-goldfinchi
O-goodingi
O-hamatus
O-hebe
O-hecabe
O-herbuloti
O-herdus
O-hildae
O-incanus
O-janeus
O-kochi
O-loesus
O-lyelli
O-maculosus
O-mayri
O-meeki
O-naias
O-nigra
O-nigripuncta
O-niphadias
O-novaguineensis
O-nuptialis
O-oxidentalis
O-perditus
O-perplexus
O-postflavida
O-postxois
O-promiscuus
O-rileyi
O-rosaceus
O-rufescens
O-salmonacea
O-serratus
O-sirpus
O-snelleni
O-spadix
O-sphragidias
O-stellans
O-subochracea
O-subvaria
O-sylvanus
O-tamsi
O-thasus
O-toxopeusi
O-tyres
O-waterhousei
O-xois
Oxycercus(incertae sedis)
Oxycrepis
O-brasiliensis
O-cordata
O-leucocera
O-schadei
Oxydactylus(EXTINCT) (incertae sedis)
Oxyelaea
O-elegans
O-heteromorpha
O-stefaniae
Oxyepoecus
O-browni
O-bruchi
O-crassinodus
O-daguerrei
O-ephippiatus
O-inquilinus
O-kempfi
O-longicephalus
O-mandibularis
O-plaumanni
O-punctifrons
O-quadratus
O-rastratus
O-reticulatus
O-vezenyii
O-vivax
Oxygastrobythus
Oxyglychus laeviventris
Oxygyrus keraudreni
Oxyhaloa
Oxyhaloinae
Oxyidris antillana(EXTINCT) (incertae sedis)
Oxyinae
Oxylidia
Oxymantis punctillata
Oxymastinocerus
Oxymonads(several genera of heterotrophic flagellates)
Oxymycterus
Oxynaspididae
Oxynetra
O-confusa
O-hopfferi
O-semihyalina
Oxynetrina
Oxynthes
O-corusca
O-viricuculla
Oxyomera
Oxyomites
Oxyopes
Oxyophthalma
O-engaea
O-giraffa
O-gracilis
Oxyophthalmellus
O-rehni
O-somalicus
Oxyopidae(lynx spiders)
Oxyopomyrmex
O-emeryi
O-gaetulus
O-insularis
O-krueperi
O-lagoi
O-oculatus
O-sabulonis
O-santschii
O-saulcyi
Oxyopsis
O-acutipennis
O-festae
O-gracilis
O-lobeter
O-media
O-obtusa
O-oculea
O-peruviana
O-rubicunda
O-saussurei
O-stali
Oxyothespinae
Oxyothespini
Oxyothespis
O-acuticeps
O-alata
O-apostata
O-bifurcata
O-brevicollis
O-brevipennis
O-dumonti
O-flavipennis
O-longicollis
O-longipennis
O-mammillata
O-maroccana
O-meridionalis
O-nilotica
O-noctivaga
O-parva
O-pellucida
O-persica
O-philbyi
O-senegalensis
O-sudanensis
O-tricolor
O-villiersi
O-wagneri
Oxypilinae
Oxypiloidea
O-subcornuta
O-tridens
Oxypilus
O-(Oxypilus)
OO-annulatus
OO-cherlonneixi
OO-descampsi
OO-distinctus
OO-enei
OO-falcatus
OO-flavicoxa
OO-gillonae
OO-guentheri
OO-hamatus
OO-lamottei
OO-montanus
OO-pallidus
OO-polyacanthus
OO-raggei
OO-tanzanicus
OO-villiersi
O-(Setoxypilus)
OS-basilewskyi
OS-burri
OS-nasutus
OS-nigericus
OS-transvalensis
Oxypius
Oxypoda
O-(Atlantoxypoda)
O-(Baeoglena)
O-(Baptopoda)
O-(Bessopora)
O-(Canaroxypoda)
O-(Cyrtonychochaeta)
O-(Demosoma)
O-(Deropoda)
O-(Disochara)
O-(Mycetodrepa)
O-(Oxypoda)
O-(Paroxypoda)
O-(Podoxya)
O-(Sedomoma)
O-(Sphenoma)
Oxypodini
Oxypodinus
Oxyporinae
Oxyruncus(sharpbill)
Oxysmilia
Oxystigma
Oxytate
Oxytelinae
Oxytelopsis
Oxytelus
Oxyteninae
Oxytenis
Oxyura(Stiff-tailed Ducks)
O-australis(Blue-billed Duck)
O-ferruginea(Andean Duck)
O-jamaicensis(Ruddy Duck)
O-leucocephala(White-headed Duck)
O-maccoa(Maccoa Duck)
O-vittata(Lake Duck)
Oxyurida
Oxyzethodes
Oxyzethus
Oyamia
Ozaena
O-boucheri
O-convexa
O-dentipes
O-ecuadorica
O-elevata
O-grossa
O-lemoulti
O-linearis
O-manu
O-martinezi
O-maxi
O-moreti
Ozaenaphaenops
Ozaeniella
Ozaenini(non-monophyletic)
Oziroeoideae
Ozmanidae
Ozotoceros bezoarticus(pampas deer)
Ozyptila
opisthokonts
other amaurobioids(funnel weavers, etc.)
other entelegynes