8 letters

Drogheda halimeda Ganymeda Monaoeda Klaipeda Klaypeda Otobreda manfreda Cinqueda ayurveda ∙ Vychegda amoebida Araneida proteida spongida squalida Annelida Phasmida peponida ∙ hydroida anaspida eucarida acrasida Madisida Diapsida Anapsida Cressida asfetida aristida Tegualda Griselda Prelanda Gullanda reddenda ∙ credenda ∙ eligenda hacienda ∙ Merienda commenda imolinda clarinda florinda anaconda ∙ wahconda ∙ Golconda ∙ caraunda profunda psychoda Kadkhoda decapoda Hexapoda Copepoda pleopoda tylopoda Lipopoda copopoda peropoda Octopoda myxopoda polypoda Oransoda Nematoda bastarda euchorda Bethesda ∙ Hanafuda

9 letters

granddada Enchilada ∙ novillada Marmolada acensuada muscavada Theravada Kishiwada haramzada ∙ Andromeda ∙ astromeda fissipeda decempeda acraspeda Bethsaida scolecida Despedida solpugida euryalida dicyemida myrianida euglenida Arachnida Opalinida Phoronida bdelloida firoloida annuloida actinoida cidaroida cydippida Syncarida planarida Lychorida echiurida ophiurida Synapsida parapsida lycopsida asafetida ∙ esmeralda Bretwalda Brunhilda Brynhilda clothilda Gualcolda Zarabanda Popaganda Karaganda Allamanda brahmanda jacaranda ∙ memoranda ∙ Tonawanda Mussaenda referenda ∙ marimonda Rosamunda Ostracoda subpagoda prememoda Myriapoda stomapoda tetrapoda physapoda plegepoda Amphipoda taxeopoda lophopoda orthopoda pagiopoda myriopoda Chilopoda Diplopoda theropoda Pteropoda pauropoda Sauropoda anisopoda physopoda pantopoda aistopoda Rhizopoda amblypoda platypoda Lemonsoda Pelmosoda Trematoda stomatoda Eucestoda dalibarda Guettarda urochorda Exochorda barracuda ∙ notanduda barriguda

10 letters

rinncefada demipomada aficionada ∙ Dhammapada genipapada tardigrada pinnigrada gravigrada laevigrada autostrada ∙ Vijayawada akhundzada Bhedabheda Avellaneda Etheldreda Tricladida Ascaridida phalangida spatangida chrysalida Priapulida limnocnida monaxonida ascidioida peracarida tubularida ephemerida Therapsida pteropsida Sauropsida phasmatida assafetida ∙ Asafoetida ∙ unigravida Brunehilda explicanda Belamcanda propaganda ∙ propoganda Karmakanda reformanda aldrovanda observanda corrigenda ∙ encomienda ∙ definienda ∙ acquirenda floribunda ∙ barramunda ∙ cynorrhoda eucopepoda malacopoda Scaphopoda gnathopoda Cheilopoda phyllopoda ancylopoda Actinopoda Heteropoda arthropoda Gastropoda Ailuropoda chaetopoda scirtopoda schizopoda Pelecypoda Hemichorda brevicauda

11 letters

Digitigrada plantigrada Polycladida Fujiyoshida antipathida sipunculida myzostomida Gregarinida pycnogonida Scorpionida tetraxonida Molluscoida spatangoida exocycloida pedipalpida Eurypterida assafoetida ∙ Goniatitida decigravida nonigravida octigravida Banyarwanda semirotunda laemodipoda gospodipoda mastigopoda ornithopoda Brachiopoda Cephalopoda poecilopoda condylopoda gasteropoda Artkhropoda stomatopoda adelochorda phonochorda protochorda Acantholyda

12 letters

Gymnamoebida myxospongida Peritrichida holotrichida hypotrichida linguatulida Pentastomida Piroplasmida diadematoida palaeocarida phyllocarida Ascaridorida sarcosporida Microsporida Sporozoasida Ichthyopsida orthonectida coloquintida ∙ nulligravida primigravida ∙ plurigravida multigravida ∙ septigravida tertigravida sextigravida Upasanakanda prememoranda zoomastigoda Branchiopoda trochalopoda euphyllopoda Anarthropoda Prosauropoda anchistopoda

13 letters

phalangigrada phytomonadida polymastigida graptolithida Archiannelida Rhabdocoelida Eugregarinida Harpacticoida holochoanoida clypeastroida Eumycetozoida Rhizopodasida quintigravida quartigravida tetradecapoda cephalochorda

14 letters

cephalodiscida protomastigida heterotrichida myxosporidiida Ornithoscelida gnathobdellida Dinoflagellida Hexactinellida centrechinoida Adenophorasida Microsporasida Secernentasida balanoglossida pantastomatida secondigravida secundigravida phytomastigoda

15 letters

parallelepipeda ∙ parallelopipeda ∙ actinomyxidiida rhynchobdellida tetractinellida Gnathustomulida trochosphaerida

16 letters

pratiyasamutpada choanoflagellida

17 letters

schizogregarinida microthelyphonida Pseudoscorpionida counterpropaganda

19 letters

Branchiogasteropoda

21 letters

Phytomastigophorasida

Words with a ∙ are valid Scrabble words (SOWPODS word list)