Kabulicornis(EXTINCT)
Kadosactis
K-roseaDanielssen 1890
Kadosanthus sulcatusCarlgren 1934
Kadsura
Kahanga
Kaindipsocus
Kaisia
Kakadu
Kakodaimonia
Kakoselia anglia(EXTINCT) (incertae sedis)
Kalidasia
Kalissus
Kallenbergia(EXTINCT)
Kallima
K-albofasciata
K-alompra
K-buxtoni
K-horsfieldi
K-inachus
K-knyvetti
K-limborgii
K-paralekta
K-philarchus
K-spiridiva
Kallimini
Kallimoides rumia
Kalophryganeidae(EXTINCT) (incertae sedis)
Kalophrynus
Kalotermes
Kalotermitidae(Drywood termites)
Kaloula
Kaltanicupes(EXTINCT)
Kaltanocoleus(EXTINCT)
Kaltenbachiella
Kamimuria
Kamptomerus
Kanakaloma
Kanakopsis
Kanala
Kanetisa(incertae sedis)
Kangiliacyathus(EXTINCT)
Kaniska
Kansasia(EXTINCT) (incertae sedis)
Kantharellidae
Kapalga
Kappapapillomavirus
Karadeniziella
Karakanocoleus(EXTINCT)
Karanasa
K-abramovi
K-alpherakyi
K-astorica
K-bolorica
K-cadesia
K-decolorata
K-eburnea
K-goergneri
K-haslundi
K-hoffmanni
K-huebneri
K-incerta
K-josephi
K-kasakstana
K-kirgizorum
K-latifasciata
K-leechi
K-maureri
K-modesta
K-mohsenii
K-moorei
K-pamira
K-praestans
K-puengeleri
K-pupilata
K-regeli
K-rohtanga
K-safeda
K-straminea
K-talastauana
K-tancrei
K-voigti
K-wilkinsi
Karanisia clarki(EXTINCT)
Karasbergia
Karauridae(EXTINCT)0(incertae sedis)
Karoophasma biedouwensis
Karoophasma botterkloofensis
Karschiidae
Karsenia koreana
Karsimatherium(EXTINCT)
Kartidris
K-ashima
K-fujianensis
K-galos
K-matertera
K-nyos
K-sparsipila
Karumia
Karumiinae
Kashmireumatidae
Kasibaeocera
Kasibelinurus(EXTINCT)
Kassina
Kassininae
Kassinula
Katanganella
Katapaussus
Katapontisus brodiei(EXTINCT) (incertae sedis)
Kathablepharids(several genera of heterotrophic flagellates)
Kathetopodion
Kathroperla
Katiannidae
Katobatizon
Katreus
Kaudernitermes
Kaupifalco(incertae sedis)
Kaveinga
K-(Angekiva)
K-(Ingevaka)
K-(Kaveinga s. str.)
K-(Vakeinga)
K-abbreviata
K-bellorum
K-cylindrica
K-fibulata
K-frontalis
K-histrio
K-kukum
K-lupata
K-lusca
K-marifuanga
K-nudicornis
K-occipitalis
K-okapa
K-orbitosa
K-parva
K-pignoris
K-poggii
K-setosa
K-stiletto
K-strigiceps
K-ulteria
K-waai
K-walfordi
Kaweshkarusa
Kayentachelys(EXTINCT)
Kazakhophotina corrupta(EXTINCT) (Mid-Cretaceous, Kzyl-Orda, Kazakhstan)
Kedestes
K-barberae
K-brunneostriga
K-callicles
K-chaca
K-heathi
K-lema
K-lenis
K-lepenula
K-macomo
K-malua
K-marshalli
K-michaeli
K-mohozutza
K-monostichus
K-nancy
K-nerva
K-niveostriga
K-pinheyi
K-protensa
K-rogersi
K-straeleni
K-sublineata
K-wallengrenii
Kekenodontidae(EXTINCT)
Kelidus bolbus(EXTINCT) (incertae sedis)
Kelleriidae
Kellicottia
Kemneria(incertae sedis)
Kemneritermes
Kempnyella
Kempynia
Kenocoelus
Kenotyphlus
Kentriodontidae(EXTINCT) (non-monophyletic) (incertae sedis)
Kentrogonida
Kenyanella
Kenyapotamus(EXTINCT) (incertae sedis)
Kenyasus(EXTINCT)
Kenyentulus
Keratella
Kermesidae(gall-like coccids)
Kerplectus
Kerriidae(lac scales)
Keteleeria
Ketupa(Brown Fish Owl and relatives)
K-flavipes(Tawny Fish Owl)
K-ketupu(Buffy Fish Owl)
K-zeylonensis(Brown Fish Owl)
Keuphyliidae(F.)
Khetania mandibulata(EXTINCT)
Khoikhoiiinae
Kiaeraspidida(EXTINCT)
Kibdelosporangium
Kickxellales
Kickxellomycotina(bread molds, Rhizopus, Mucor, etc.)
Kiera
Kigatrodes
Kilbuchophyllida(EXTINCT)
Kilimatyphlus
Kimoda
Kineococcus
Kineosphaera
Kineosporia
Kinnaridae
Kinorhyncha
Kioloa
Kionotrochus
Kiotina
Kirghizocupes cellulosus(EXTINCT)
Kirinia
K-climene
K-epaminondas
K-epimenides
K-eversmanni
K-roxelana
Kirkiaceae
Kirtland Shale aublysodontine(EXTINCT)
Kishinouyeum
K-breve
K-cornuta
K-hepatica
K-jianfenglingensis
K-parvula
K-robusta
K-sinensis
K-stigmosus
Kissister
Kistneria
Kistneriella
Kistnerium
Kitasatospora
Kizylkuma(EXTINCT)
Kladotyphlus
Klamathia
Klapalekia
Klebsormidiales
Kleptisister
Kliellidae
Klimeschia
Klugieae
Klugipaussus
Knoellia
Koalliella(EXTINCT)0(incertae sedis)
Kobikeryx(EXTINCT)
Kobrona
K-[species A]
K-croma
K-denva
K-edfina
K-eva
K-idea
K-infralutea
K-kobros
K-lexa
K-mirza
K-pansa
K-rasta
K-sebana
K-sota
K-tabella
K-vanda
K-vasna
K-wama
K-zadma
Kobus ellipsiprymnus(waterbuck)
Kobus kob(kob)
Kobus leche(red lechwe)
Kobus megaceros(Nile lechwe)
Kobus vardonii(puku)
Kocuria
Koeberliniaceae
Kogiidae(pygmy/dwarf sperm whales)
Koilomera
Kokiriidae
Kokomopteridae(EXTINCT)
Kokomopteroidea(EXTINCT)
Koleolepadidae
Kolkwitzia
Kolpochoerus(EXTINCT)
Kolwezia
Komba robustus(EXTINCT)
Komokiacea(large marine amoebae)
KondakoviaFilippova, 1972
Kongobatha
K-diademata
K-papua
Koompassia Martiodendron, Androcalymma, Kalappia, (monophyly uncertain)
Korarchaeota
Kordiimonas gwangyangensis
Korenia margaritaceusDanielssen 1890
Korovodes
Korscheltellus
K-gracilis
K-lupulina
Koruthaialos
K-butleri
K-focula
K-rubecula
K-sindu
Korynochoerus(EXTINCT)
Kostea
Kotlassia(EXTINCT)
Kotshkorkia laticeps(EXTINCT) (incertae sedis)
Kotujellitinae(EXTINCT)
Kraepelinia
Krameria
Kribbella
Kricogonia
K-cabrerai
K-lyside
Krishnacapritermes
Krithidae
Krohnitta
K-pacifica
K-subtilis
Krohnittella
K-boureei
K-tokiokai
Kroyeriidae
Kruia
Kubanochoerinae(EXTINCT)
Kubanochoerus(EXTINCT)
Kubanotragus(EXTINCT)
Kuehneosauridae(EXTINCT)
Kuiterichthys
Kumothales inexpectata
Kunsia(water rat and South American giant rats)
Kupeus
Kuriporus
Kurthia
Kuschelidium
Kuschelinus insularius
Kuscheliotes
Kutzneria
Kuyangichthidae(EXTINCT)
Kyarranus
Kyogle
Kyphopteryx
Kyrinion martilli(EXTINCT)
Kyromyrma neffi(EXTINCT) (incertae sedis)
Kyrtoxyna
Kytococcus
koala lemurs(EXTINCT)