Uchidanurinae
Udaiana cynis(incertae sedis)
Udaspes
U-folus
U-stellata
Udranomia
U-eurus
U-kikkawai
U-orcinus
U-spitzi
Udvardya
Uenohadesina
Uenoidae
Uittienia Dialium, Dicornynia, (monophyly uncertain)
Ulisseus
Ulkeopsis
Ulkeus
Ulmaceae(elm family)
Ulmeriella(EXTINCT) (incertae sedis)
U-aquisextana(EXTINCT) (Upper Oligocene of France)
U-bauckhorni(EXTINCT) (Upper Oligocene of Germany)
U-cockerelli(EXTINCT) (Upper Oligocene of Siberia)
U-latahensis(EXTINCT) (Upper Miocene of Washington, USA)
U-martynovi(EXTINCT) (Lower Miocene of Germany)
U-pliocenica(EXTINCT) (Mio-Pliocene of France)
U-rubiensis(EXTINCT) (Oligocene of Montana, USA)
U-shizukuishiensis(EXTINCT) (Upper Miocene of Japan)
U-straussi(EXTINCT) (Pliocene of Germany)
U-uemurai(EXTINCT) (Upper Miocene of Japan)
U-willershausensis(EXTINCT) (Pliocene of Germany)
Uloboridae(hackled-band orb weavers)
Ulocymus
Ulodidae
Ulommia
Ultratitan(EXTINCT)
Uluella
Ulugurubythus
Ulvophyceae
Umbra krameri
Umbra limi
Umbra pygmae
Umbravirus
Umenocoleidae
Umenocoleus(EXTINCT)
Umoricoleus perplex(EXTINCT)
Unamis
Uncertainly placed genera
Uncertainly placed orders and families of Dothideomycetes(non-monophyletic)
Uncopaederus
Undiatina(EXTINCT)
Unguitermes
Uniclavus zambezensis
Unicornitermes
Unidentates
Unidentified Dendryphantinae
Unidentified Euophryinae
Unidentified Hyetussinae
Unipeltata
Unkana
U-ambasa
U-mytheca
Unumgar
Uperodon
Uperoleia
Upupidae(hoopoes)
Uraarachne
Uralelytron(EXTINCT)
Uralia(EXTINCT)
Uralocoleus(EXTINCT)
Uralocupes major(EXTINCT)
Uraloptysmatidae(EXTINCT)
Uraniidae(swallowtail moths)
Uranomys
Uratelornis chimaera(Long-tailed Ground Roller)
Urbanus
U-albimargo
U-ambiguus
U-belli
U-carmelita
U-chalco
U-chales
U-cindra
U-dorantes
U-doryssus
U-dubius
U-elmina
U-esma
U-esmeraldus
U-esta
U-evenus
U-evona
U-huancavillcas
U-longicaudus
U-magnus
U-parvus
U-procne
U-prodicus
U-pronta
U-pronus
U-proteus
U-reductus
U-simplicius
U-tanna
U-teleus
U-velinus
U-villus
U-virescens
U-viridis
U-viterboana
U-zagorus
Ureaplasma
Ureibacillus
Urepus
Urgineoideae
Urmiatherium(EXTINCT)
Urochordata(tunicates)
Urochordeumatidae
Urocopiidae
Urocoras
Uroctonites
Uroctonus
Urodacidae
Urodidae(false burnet moths)
Urodonia
Urogale everetti(Philippine tree shrew)
Uroglaux dimorpha(Papuan Hawk-Owl)
Urolitus
Uromys
Urophonius
Uroplectes
Uropsalis(Swallow-tailed Nightjar and relatives)
U-lyra(Lyre-tailed Nightjar)
U-segmentata(Swallow-tailed Nightjar)
Urosaurus(tree lizards)
Urostylidae
UroteuthisRehder, 1945
U-(subgenus uncertain) pickfordi
U-(subgenus uncertain) reesi
U-abulati
U-arabica
U-bengalensis
U-chinensis
U-duvaucelii
U-edulis
U-robsoni
U-singhalensis
U-vossi
U-(Aestuariolus) nocticula
U-(Photololigo)
U-(Uroteuthis) bartschi
U-sibogae
Urotriainus
Urotriorchis(incertae sedis)
Urozethidius
Ursidae(bears and giant panda)
Urticaceae(nettle family) (non-monophyletic)
Urticina antarcticaVerrill 1922
Urticina callosaVerrill 1882
Urticina carlgreniClubb 1902
Urticina columbianaVerrill 1922
Urticina perdixVerrill 1882
Urticina sulcataClubb 1902
Urticinopsis
U-crassaCarlgren 1928 [sic]
Urumqia liudaowanensis(EXTINCT)
Usiinae
Ustilaginomycotina(smut fungi)
Uta
Utacapnia
Utaperla
Utegenia shpinari(EXTINCT)
Uzelothripidae