Xanadoses nielseni
Xaniopyramis(EXTINCT)
Xanthocephalus xanthocephalus(Yellow-headed Blackbird)
Xanthocorynus
Xanthodermus
Xanthodisca
X-ariel
X-astrape
X-rega
X-vibius
Xantholinini
Xantholinus
X-(Afrolinus)
X-(Calolinus)
X-(Helicophallus)
X-(Heterolius)
X-(Idiolinus)
X-(Meneidophallus)
X-(Milichilinus)
X-(Neoleptophallus)
X-(Paracyclinus)
X-(Polydontophallus)
X-(Purrolinus)
X-(Stenophallus)
X-(Tetralinus)
X-(Toxophallus)
X-(Typhlolinus)
X-(Xantholinus)
Xanthomantis
X-(Oligocanthopus) ornata
X-(Pliacanthopus) mantispoides
X-(Xanthomantis)
XX-bimaculata
XX-flava
XX-malayana
Xanthoneura
Xanthonomus
Xanthophius
Xanthophytes
Xanthopsar flavus(Saffron-cowled Blackbird)
Xanthopygina
Xanthopygoides
Xanthopygus
Xanthorrhoeaceae
Xanthosphaera
Xanthotaenia busiris
Xarifiidae
Xenadiastus
Xenalluaudia
Xenandra
X-agria
X-ahrenholzi
X-desora
X-heliodes
X-helius
X-mielkei
X-nigrivenata
X-pelopia
X-poliotactis
X-vulcanalis
Xenanthobium
Xenasteiidae
Xenastenoglossa
Xenaster
Xenelytron(EXTINCT)
Xeniades
X-chalestra
X-ethoda
X-orchamus
X-victoria
Xenicopoda
Xenidus
Xenion
Xenister
Xenistusa
Xenobasilewskyia
Xenobatrachus
Xenobatrisus
Xenobesuchetia
Xenobiota
Xenobius
Xenobryaxis
Xenobythus
Xenocelisia
Xenocliarthrus
Xenococcus
Xenocoelomatidae
Xenoconurus
Xenodusa
Xenogaster
Xenoglaux loweryi(Long-whiskered Owlet)
Xenogmocerodes
Xenogyna
Xenogynidia
Xenohyus(EXTINCT)
Xenokrohnia sorbei
Xenolejeunea
Xenoleleupia
Xenomachadoella
Xenomedon
Xenomma
Xenomussardia
Xenomyrmex
X-floridanus
X-panamanus
X-stollii
Xenonychus(2 species)
Xenopelta
Xenoperdix udzungwensis(Udzungwa Forest Partridge)
Xenophanes
Xenophilothis(1 species)
Xenophoroidea
Xenophyophores(large marine amoebae)
Xenopteryx
Xenopus
Xenopus pascuali(EXTINCT)
"Xenopus" romeri
Xenopygia
Xenopygiella
Xenopygus
Xenorhina
Xenosauridae
Xenosiphon0(incertae sedis)
Xenosiren(EXTINCT)
Xenotmesiphorus
Xenotrecha huebneri
Xenotrichulidae
Xenotyphlus
Xenozorotypus burmiticus(EXTINCT) (Cretaceous)
Xerhius
Xerinae
Xerini(African and long-clawed ground squirrels)
Xerolobium
Xerolycosa
Xeromelissinae
Xeromphalina
Xeromys
Xeronemataceae
Xerophygus
Xerosaprinus(~25 species)
Xerus
Xestipyge
Xestoblatta
Xestoleberididae
Xestolinus
Xestonotus
Xesturida
Xhoaphryx lemeei
Xhosores
Xiaitermes
Xipapillomavirus
Xiphinematobacter
Xiphobythus
Xiphocentronidae
Xiphodontidae(EXTINCT)
Xiphosura(horseshoe crabs)
Xiphosurida
Xiphozelinae
Xiphydrioidea
Xispia
X-quadrata
X-satyrus
Xiushuiaspis(EXTINCT)
Xosablatta
Xosaia
Xotidium
Xybarida
Xybaris
Xyelinae
Xylanibacterium
Xylanimonas
Xylion
Xylionopsis
Xylionulus
Xyliphius
X-barbatusde Armburu & Armburu, 1962
X-kryptosTaphorn & Lilyestrom, 1983
X-lepturusOrcés, 1962
X-lombarderoiRisso & Risso 1964
X-magdalenaeEigenmann 1912a
X-melanopterusOrcés, 1962
Xylobiops
Xyloblaptus
Xylobosca
Xylochomitermes
Xylocis
Xylocopinae(carpenter bees)
Xylocopini
Xylodectes
Xylodeleis
Xylodromus
Xylodrypta
Xylogenes
Xylomedes
Xylomeira
Xylomyidae
Xylonaeus
Xylopertha
Xyloperthella
Xyloperthini
Xyloperthodes
Xylophagidae
Xylophorus
Xyloprista
Xylopsocus
Xylostega
Xylostiba
Xylothrips
Xylotillus
Xynia lilacina
Xynia lithosina
Xynias
Xyphiopsyllidae
Xyphosternum(EXTINCT)
Xyronotidae
Xysticus
Xystosomina
Xystosomus
X-convexus
X-impressifrons
X-inflatus
X-laevimicans
X-laevis
X-niger
X-paralaevis
X-tholus
X-turgidus
Xystropeltis
X-lankesteri
X-meridionalis
X-quadrilobata
Xyts