5 letters:
boris, coris, doris, dorus, foris, goris, horus, joris, korus, lores, loris, lorus, moris, morus, noris, orris, porus, soris, sorus, toris, torus, voris, zoris

6 letters:
acorus, boris', borris, cloris, dorice, dorris, floris, florus, forres, for us, horace, kauris, laurus, maurus, morice, morris, norice, norris, orrice, porous, saurus, sorice, sporus, taurus, torose, torras, tsoris, turris

7 letters:
-saurus, chloris, delores, dolores, doloris, laurice, lycoris, morrice, morris', morriss, nourice, ptloris, pylorus, sporous

8 letters:
botaurus, chlorous, clitoris, clitorus, diodorus, eosaurus, mcmorris, metaurus, nourrice, petaurus, prioress, sartoris

9 letters:
adasaurus, authorise, before us, corchorus, epidaurus, liquorice, mantorras, montgoris, mussaurus, polyborus, polydorus, polyporus, prochorus, rectoress, sepphoris, squarrous, thesaurus, tortorice, urosaurus

10 letters:
allosaurus, atlasaurus, aucasaurus, barosaurus, bos taurus, centauress, cyclosorus, dakosaurus, dinosaurus, dryosaurus, fitzmorris, gasosaurus, gorosaurus, heliodorus, laetiporus, lotosaurus, mapusaurus, mauisaurus, megasaurus, mesosaurus, minotaurus, mixosaurus, morosaurus, mosasaurus, mososaurus, nanosaurus, nigroporus, nodosaurus, oligoporus, ophisaurus, pliosaurus, poposaurus, rajasaurus, restore us, sceloporus, semichorus, silesaurus, sinosaurus, slow loris, torosaurus, tylosaurus, uredosorus, xenosaurus

11 letters:
alamosaurus, amurosaurus, anteosaurus, apatosaurus, archosaurus, artemidorus, athenodorus, bulbasaurus, camptosorus, carnotaurus, cassiodorus, cetiosaurus, cistothorus, dean norris, dipsosaurus, einiosaurus, fitzmaurice, genus loris, gorgosaurus, hadrosaurus, hydrosaurus, icarosaurus, isanosaurus, kamuysaurus, kritosaurus, kronosaurus, limaysaurus, luchasaurus, lurdusaurus, nanuqsaurus, nigersaurus, nothosaurus, nyasasaurus, nyctosaurus, ophiotaurus, paleosaurus, philochorus, phylloporus, pleiosaurus, pleurosorus, pseudacorus, purussaurus, saltasaurus, sarahsaurus, sarcosaurus, scutosaurus, segnosaurus, shunosaurus, siamosaurus, spinosaurus, stegosaurus, stesichorus, suchosaurus, supersaurus, tarbosaurus, teleosaurus, three-torus, thryothorus, torvosaurus, turiasaurus, ultrasaurus

12 letters:
amargasaurus, ampelosaurus, ankylosaurus, bajadasaurus, basilosaurus, brontosaurus, camarasaurus, camptosaurus, centrosaurus, ceratosaurus, chasmosaurus, chindesaurus, chuck norris, denversaurus, dryptosaurus, dyoplosaurus, edaphosaurus, elasmosaurus, erlikosaurus, eunotosaurus, europasaurus, eye of horus, futabasaurus, gojirasaurus, hydrochoerus, hylaeosaurus, kentrosaurus, lambeosaurus, lando norris, lystrosaurus, maquiladoras, megalosaurus, ouranosaurus, parksosaurus, pinacosaurus, pisanosaurus, plateosaurus, plesiosaurus, puertasaurus, qantassaurus, rapetosaurus, seismosaurus, shastasaurus, sonorasaurus, stellasaurus, teratosaurus, tetragonurus, titanosaurus, vespersaurus, wuerhosaurus

13 letters:
achelousaurus, albertosaurus, alectrosaurus, arizonasaurus, bahariasaurus, brachiosaurus, cadborosaurus, champsosaurus, charonosaurus, chrysochloris, corythosaurus, cyclotosaurus, daemonosaurus, dicraeosaurus, dilophosaurus, dolichosaurus, dromaeosaurus, edmontosaurus, elaphrosaurus, genus chloris, gigantosaurus, herrerasaurus, ichthyosaurus, lesothosaurus, lufengosaurus, magyarosaurus, majungasaurus, nipponosaurus, panoplosaurus, proterosaurus, savannasaurus, scelidosaurus, scomberomorus, shringasaurus, slender loris, styracosaurus, tenontosaurus, trematosaurus, tyrannosaurus, zephyrosaurus

14 letters:
anodontosaurus, chlamydosaurus, crichtonsaurus, cristatusaurus, daspletosaurus, doch-an-dorris, eromangasaurus, giganotosaurus, huayangosaurus, incisivosaurus, mastodonsaurus, psittacosaurus, qianzhousaurus, scutellosaurus, staurikosaurus, thescelosaurus

15 letters:
argentinosaurus, camarillasaurus, cryolophosaurus, metridiochoerus, monolophosaurus, ophthalmosaurus, petrolacosaurus, proceratosaurus, pycnonemosaurus, shantungosaurus, therizinosaurus, tuojiangosaurus

16 letters:
acrocanthosaurus, appalachiosaurus, ekrixinatosaurus, futalognkosaurus, muttaburrasaurus, pachyrhinosaurus, sigilmassasaurus, sinornithosaurus, stenonychosaurus, temnodontosaurus, thecodontosaurus, yangchuanosaurus

17 letters:
bruhathkayosaurus, genus stegosaurus, gigantspinosaurus, haplocanthosaurus, heterodontosaurus

18 letters:
genus brontosaurus, metriacanthosaurus, pachycephalosaurus

19 letters:
carcharodontosaurus, genus tyrannosaurus

23 letters:
micropachycephalosaurus

4 letters:
iris

5 letters:
virus, pyrus, purus, cyrus, gyrus, ceras, larus, parus

6 letters:
acarus, cirrus, nereus, merits, aurous, purace

7 letters:
peeress, heiress, terrace, starets, polaris, ferrous, belarus, sciurus, ailurus, carrots, cuirass, luvarus, lyrurus, ocyurus, papyrus, pirates, pyrrhus, seiurus, silurus, tapirus

8 letters:
honduras, desirous, arcturus, ichorous, ameiurus, byelarus, dasyurus, hesperis, lathyrus, leonurus, micrurus, necturus, paliurus, pipturus, reovirus, triturus

9 letters:
myxovirus, embarrass, atherurus, automeris, baccharis, centaurus, conilurus, dinoceras, echovirus, palinurus, psithyrus, quakeress

10 letters:
slow virus, retrovirus, alopecurus, dutch iris, dwarf iris, eleocharis, genus iris, parvovirus, poliovirus, polycirrus, raphicerus, undesirous

11 letters:
tumor virus, ebola virus, actinomeris, alepisaurus, callisaurus, german iris, hydrocharis, low spirits, paradoxurus, plant virus, rhabdovirus, tetrapturus, vernal iris, yellow iris

12 letters:
bearded iris, herpes virus, picornavirus, disembarrass, high spirits, animal virus, bulbous iris, deinocheirus, english iris, menticirrhus, persian iris, spanish iris, sternotherus, tamiasciurus

13 letters:
millionairess, japanese iris, paramyxovirus, stinking iris

14 letters:
ardent spirits, dalmatian iris, in low spirits, orthomyxovirus, smallpox virus

15 letters:
neutral spirits, cytomegalovirus, florentine iris, in good spirits, in high spirits

16 letters:
british honduras

17 letters:
hepatitis a virus, wound tumor virus

19 letters:
herpes zoster virus

20 letters:
herpes simplex virus, tobacco mosaic virus

21 letters:
human papilloma virus

22 letters:
judgment on the merits

23 letters:
judgement on the merits

28 letters:
human immunodeficiency virus