**3. Results**

*Key to Families and Genera of Gastrotricha*

**1a** Body flask-, bottle- or tenpin-shaped; posterior body region usually furcate (furca), less often rounded off or bifurcate; cuticle usually forming ornamentations such as scales and spines; TbA, TbD, and TbL absent; TbP present, numbering 2 (rarely 4 or 0) at the distal end of the furcal rami; mouth narrow; pharynx lacking pores. Freshwater, marine, and brackish: periphytic, epibenthic, and interstitial, occasionally semiplanktonic. Order CHAETONOTIDA, Suborder PAUCITUBULATINA (Figure 1A–C) ... ... ... ... ... ... . ... ... ... ... ... ... . ... ... .... **38 1b** Different from the above. ... .. ... ... ... ... ... ... ... ... ... ... ... ... ... .... ... ... ... .... **2**

**Figure 1.** Drawings of hypothetical Chaetonotida: (**A–C**) Paucitubulatina and (**D**) Multitubulatina (*Neodasys*). (**A**) Habitus, dorsal view; (**B,C**) anterior region, ventral view, showing different arrangement of the locomotor ciliations. Abbreviations: **Ce**, cephalion; **Ci**, locomotor cirri; **eg**, egg; **Fu**, furca; **HC**, hemoglobin-containing cell; **Hy**, hypostomion; **In**, intestine; **LC**, locomotor cilia; **Mt**, mouth; **Ph**, pharynx; **PhIJ**, pharyngo-intestinal junction; **Pl**, pleuria; **SB**, sensorial bristle; **SC**, sensorial cilia; **sk**, scales with a keel; **sns**, scales with notched spines; **Sh**, spermatophores; **Sp**, spermatozoa; **ss**, scales smooth; **sss**, scales with simple spines; **sts**, scale with a stalk; **TbL**, lateral adhesive tubes; **TbP**, posterior adhesive tubes. (**A**–**C**), original; scales redrawn and modified from [38]; (**D**), redrawn and modified from [39].


**Figure 2.** Drawing of a hypothetical Macrodasyida. (**A**) Habitus showing the internal organs, dorsal view; (**B**) anterior region, ventral view, showing some of the possible arrangements of adhesive tubes of the anterior series, i.e., borne, singly, directly from the body surface (the two most anterior ones), and borne in a group on a fleshy extensible base (the posterior one); (**C–E**), some of the possible configurations of the posterior region, ventral view; (**F**) some of the possible spines and scales found among Macrodasyida. Abbreviations: **AAO**, accessory adhesive organs; **An**, anus; **CO**, caudal organ; **Eg**, egg; **Fo**, frontal organ; **In**, intestine; **LS**, leaf-like sensorial organ; **Ph**, pharynx; **PhIJ**, pharyngo-intestinal junction; **PhP**, pharyngeal pores; **PS**, piston pit sensorial organ; **TbA**, anterior adhesive tubes; borne singly, directly from the body; **TbP**, posterior adhesive tubes; **TbVL**, ventrolateral adhesive tubes; **Te**, testicle. (**A–C**) original; (**D**) modified from [13]; (**E**) modified [15].


**Figure 3.** Macrodasyida, Dactylopodolidae: models of (**A**) *Dactylopodola*, (**B**) *Dendropodola*, and (**C**) *Dendrodasys*. Scale bars = 100 μm. (**A**) from [40] with modifications, (**B**) from [41] with modifications, and (**C**) from [42] with modifications.


**Figure 4.** Macrodasyida, Xenodasyidae: models of (**A**) *Xenodasys* and (**B**) *Chordodasiopsis*. Scale bars = 200 μm. (**A**) from [39] with modifications, (**B**) from [43] with modifications.


**Figure 5.** Macrodasyida, Cephalodasyidae: models of (**A**) *Cephalodasys*, (**B**) *Pleurodasys*, (**C**) *Mesodasys*, (**D**) *Dolichodasys*, and (**E**) *Paradasys*. Scale bars = 200 μm. (**A**–**D**) from [39] with modifications, (**E**) from [35] with modifications.


**15b**(14b) Accessory adhesive tubes present, close to the PhIJ. Rare; marine: interstitial. ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... .. ... ... *Prostobuccantia* (Figure 6D)

**Figure 6.** Macrodasyida, Turbanellidae: models of (**A**) *Dinodasys*, (**B**) *Pseudoturbanella*, (**C**) *Paraturbanella*, (**D**) *Prostobuccantia*, (**E**) *Turbanella*, and (**F**) *Desmodasys*. Scale bars = 200 μm. (**A**) from [44] with modifications, (**B**) from [39] with modifications, (**C**) from [45] with modifications, (**D**) from [46] with modifications, and (**F**) from [47] with modifications.


**Figure 7.** Macrodasyida, Macrodasyidae: models of (**A**) *Kryptodasys*, (**B**, **C**) *Thaidays*, (**D**) *Macrodasys*, and (**E**) *Urodasys*. Scale bars: (**A–C**) = 100 μm, (**D**, **E**) = 200 μm. (**A**) from [15] with modifications, (**B**,**C**) from [14] with modifications, and (**D**, **E**) from [39] with modifications.


**Figure 8.** Macrodasyida, Lepidodasyidae: model of *Lepidodasys*. Scale bar = 200 μm. From [39] with modifications.


**Figure 9.** Macrodasyida, Thaumastodermatidae: models of (**A**) *Diplodasys*, (**B**) *Oregodasys*, (**C**) *Acanthodasys*, (**D**) *Pseudostomella*, (**E**) *Thaumastoderma*, (**F**) *Tetranchyroderma*, (**G**) *Ptychostomella*, and (**H**) *Hemidasys*. Scale bars: (**A**–**F**, **H**) = 200 μm, (**G**) = 50 μm. (**A**) from [48] with modifications, (**B**–**F**) from [39] with modifications, (**G**) from [41] with modifications, and (**H**) from [49] with modifications.


**Figure 10.** Macrodasyida, Redudasyidae: models of (**A**) *Anandrodasys* and (**B**) *Redudasys*. Scale bars = 50 μm. (**A**) from [50] with modifications, (**B**) from [51] with modifications.


**Figure 11.** Macrodasyida, Hummondasyidae: model of *Hummondasys.* Scale bars = 100 μm. From [13] with modifications.


**Figure 12.** Macrodasyida, Planodasyidae: models of (**A**) *Megadasys*, (**B**) *Planodasys*, and (**C**) *Crasiella*. Scale bars = 200 μm. From [39] with modifications.



**Figure 13.** Macrodasyida, INCERTAE SEDIS: model of *Marinellina*. Scale bar = 50 μm. From [52] with modifications.


**Figure 14.** Chetonotida, Xenotrichulidae: models of (**A**) *Heteroxenotrichula,* (**B**) *Draculiciteria*, and (**C**) *Xenotrichula*. Scale bars = 50 μm. (**A**, **C**) modified from [35], (**B**) modified from [53].


**Figure 15.** Chetonotida: (**A**) Dichaeturidae, a model of *Dichaetura*. (**B, C**) Proichthydiidae, models of (**B**) *Proichthydium* and (**C**) *Proichthydioides*. Scale bars = 50 μm. (**A**) from [54] with modification, (**B**) from [55] with modification, and (**C**) re-sketched from [56].


**Figure 16.** Chetonotida, Chaetonotidae: models of (**A**) Undula, (**B**) Cephalionotus, (**C**) Polymerurus, (**D**) Arenotus, (**E**) Caudichthydium, (**F**) Ichthydium, (**G**) Aspidiophorus, (**H**) Heterolepidoderma, (**I**) Lepidodermella, (**L**) Fluxiderma, (**M**) Rhomballichthys, (**N**) Lepidochaetus, and (**O**) Halichaetonotus. Scale bars (**A**, **C**–**D**) = 50 μm, (**B**) = 25 μm. (**A**) from [57] with modifications, (**B**) from [37] with modifications, (**C**) from [51] with modifications, (**D**) from [58] with modifications, (**E**–**H**, **M**) from [54] with modifications, (**I**, **L**) from [59] with modifications, and (**O**) from [60] with modifications.



**Figure 17.** Chaetonotida, Chaetonotidae: models of (**A**) *Chaetonotus* and (**B**) *Bifidochaetus*. Scale bars (**A**) = 50 μm, (**B**) = 10 μm. (**A**) from [61] with modifications, (**B**) from [62] with modifications.


restricted to a small patch on the ventral side. Uncommon to rare; freshwater: hyperbenthic and semiplanktonic. NEOGOSSEIDAE (Figure 18) ... ... ... ... . ... ... . ... ... ... ... .. **61 60b**(41b) Posterior body region rounded or truncated, occasionally with a very short caudal lobe or paired postero-lateral protuberance; head without tentacles; body scales reduced or absent; trunk bearing very long and movable spines arranged into groups. Uncommon to rare; freshwater: hyperbenthic, epibenthic, and semiplanktonic. DASYDYTIDAE (Figure 19)... **62**

**Figure 18.** Chaetonotida, Neogosseidae: models of (**A**) *Neogossea* and (**B**) *Kijanebalola*. Scale bars = 50 μm. (**A**) from [54] with modifications, (**B**) from [57] with modifications.


**Figure 19.** Chaetonotida, Dasydytidae: models of (**A**) *Anacanthoderma*, (**B**) *Ornamentula*, (**C**) *Stylochaeta*, (**D**) *Dasydytes*, (**E**) *Haltidytes*, and (**F**) *Setopus*. Scale bars = 50 μm. (**A**, **F**) from [54] with modifications, (**B**–**E**) from [57] with modifications.


**Figure 20.** Chetonotida, Muselliferidae: models of (**A**) *Musellifer* and (**B**) *Diuronotus*. Scale bar = 200 μm. From [39] with modifications.
