Rev 10/24/2022
(Compiled from Decraemer and Smol, 2011; De Ley and Blaxter 2002, 2004, 2006; Maggenti, 1981; and lectures by Maggenti, 1992)
| 1 | a |
|
Class: Enoplea | go to 2 |
| b | Esophagus often subdivided into bulbs; amphid apertures on lips, often difficult to see, or posterior to lips and obvious - round or coiled; gonads single or paired in both male and female | Class: Chromadorea | go to 8 | |
| 2 | a | Anterior sensillae often in 3 whorls of inner labial papillae, outer labial setae and cephalic setae; metanemes (filamentous structures in lateral chors) present; caudal glands present; esophageal glands open in or near stoma | Sub-class: Enoplia | go to 3 |
| b | Anterior sensillae rarely setiform; stoma with teeth or odontostyle; esophagus cylindrical, bottle-shaped or a stichosome; caudal glands usually absent; esophageal glands open in posterior region of esophagus | Sub-class: Dorylaimia | go to 4 | |
| 3 | a | Spicule protractor muscles attached to proximal enlargement; metanemes present; marine and fresh water | Enoplida | go to 10 |
| b | Spicule protractor muscles form a pouch around spicules; protrusible tooth in some forms | Triplonchida | go to 11 | |
| 4 | a | Movable hollow spear; esophagus expanded posteriorly - bottle-shaped. | Dorylaimida | go to 12 |
| b | Glandular esophageal stichosome and intestinal trophosome; juveniles are parasites of invertebrates. | Mermithida | go to 15 | |
| c | Esophagus vestigial; parasites of vertebrates in all life stages | Muspiceida | go to 17 | |
| d | Esophagus cylindrical throughout | go to 5 | ||
| 5 | a | Juveniles are parasites of invertebrates; adults free-living | Marimermithida | go to 19 |
| b | All stages parasitic; adults are vertebrate parasites, juveniles with or without intermediate hosts | go to 6 | ||
| c | All stages free-living | go to 7 | ||
| 6 | a | Posterior esophagus a stichosome; onchiostyle present; monovarial; anphids pore-like | Trichinellida | go to 16 |
| b | Anterior end has a sucker; males with bell-shaped bursa | Dioctophymatida | go to 18 | |
| 7 | a | Strong, large, cuticularized stoma with prominent dorsal tooth; predators of nematodes | Mononchida | go to 13 |
| b | Long and slender; tubular stoma without teeth; stoma without lips; soil inhabitants | Isolaimiida | go to 14 | |
| 8 | a | Amphids usually pore-like, on lips; cephalic sensillae on lip region; phasmids present; caudal glands absent; mainly terrestrial, rarely freshwater or marine; include free-living, animal parasites, plant parsites | Rhabditida | go to 26 |
| b | Amphids post-labial, varied shapes; phasmids absent; somatic seta common; mainly free-living aquatic organisms | go to 9 | ||
| 9 | a | Anterior sensillae in three whorls, inner labial, outer labial and cephalic; amphids var from circular to complex spirals, post-labial and usually posterior to cephalic setae; stoma funnel-shaped with a dorsal tooth and two smaller subventral teeth; esophagus cylindrical with posetrior bulb; females diovarial; mainly marine | Chromadorida | go to 20 |
| b | Brownish cuticle; anterior sensillae in three whorls, inner labial, outer labial and cephalic; amphids spiral, posterior to cephalic setae; dorsal and smaller subventral teeth; esophagus cylindrical with enlarged end bulb | Desmodorida | go to 21 | |
| c | Anterior sensillae in three whorls, inner labial, outer labial and cephalic, cephalic setae on peduncles; amphids large, on head; ocelli may be present; small stoma with small teeth; esophagus cylindrical; females diovarial; mainly marine | Desmoscolecida | go to 23 | |
| d | Small, slender nematodes with a slender tail region; three whorls of anterior sensilla; amphids round; both sexes with one or two gonads; Mainly aquatic and wet soil environments | Monhysterida | go to 22 | |
| e | Anterior sensillae in three whorls, inner labial, outer labial and cephalic; stoma with 3 to 6 teeth on anterior edge; amphids loop-shaped; ocelli may be present; esophagus cylindrical with no posterior enlargement | Araeolaimida | go to 24 | |
| f | Labial sensilla papilliform, cephalic sensilla usually setiform; qamphids circular or simple spiral; esophagus cylindrical, with or without basal bulb; females usually diovarial | Plectida | go to 25 | |
| 10 | a | Enoplida; amphids pocket-shaped; esophagus cylindrical; 3 esophageal glands opening in or near stoma; excretory canal present; marine and freshwater | Enoplina | |
| b | Enoplida; amphids pocket-shaped; stoma elongated, without teeth or with 3-5 moveable teeth; esophagus cylindrical; excretory canal present; mainly marine but also freshwater | Ironina | ||
| c | Enoplida; amphids pocket-shaped; stoma large, refractive, with 3 teeth; esophagus cylindrical; excretory canal present; mainly marine but also freshwater | Oncholaimina | ||
| d | Enoplida; amphids spiral; stoma with 1 or more teeth; esophagus cylindrical; females diovarial; mainly marine | Tripyloidina | ||
| e | Enoplida; amphids pocket-shaped; stoma with dorsal tooth; esophagus cylindrical with terminal bulb; excretory canal present; females diovarial; soil and freshwater inhabitants | Campydorina | ||
| f | Enoplida; amphids pore or pocket-shaped; stoma vestigial, without teeth; esophagus slender, cylindrical, enlarged posteriorly; soil and freshwater inhabitants | Alaimina | ||
| g | Enoplida; amphids spiral; stoma with teeth; esophagus cylindrical; females diovarial; mainly marine, some freshwater | Trefusiina | ||
| 11 | a | Triplonchida; stoma with curved or complex spear; sensilla papilliform; esophagus with elongate prosterior bulb | Diphtherophorina | |
| b | Triplonchida; stoma wide and refractive or funnel-shaped; usually with teeth; spinneret at tail tip | Tobrilina | ||
| c | Triplonchida; stoma narrow with a dirsal and two small subventral teeth; well-developed caudal glands opening at terminal spinneret | Tripylina | ||
| 12 | a | Dorylaimida; stoma with axial odontostyle | Dorylaimina | |
| b | Dorylaimida; stoma withgrooved subventral mural tooth | Nygolaimina | ||
| 13 | a | Mononchida; stoma large, wide with 1 to 3 teeth and/or rows of denticles | Mononchina | |
| b | Mononchida; Stoma narrow with a single subventral tooth | Bathyodontina | ||
| 14 | a | Isolaimiida; | Isolaimiina | |
| 15 | a | Mermithida; | Mermithina | |
| 16 | a | Trichinellida; | Trichinellina | |
| 17 | a | Muscipeicida; | Muscipeicina | |
| 18 | a | Dioctophymatida; | Dioctophymatina | |
| 19 | a | Marimermithida; | Marimermithina | |
| 20 | a | Chromadorida; | Chromadorina | |
| 21 | a | Desmodorida; | Desmodorina | |
| 22 | a | Monhysterida; | Monhysterina | |
| b | Monhysterida; | Linhomoeina | ||
| 23 | a | Desmoscolecida; | Desmoscolecina | |
| 24 | a | Araeolaimida; | Araeolaimina | |
| 25 | a | Plectida; | Plectina | |
| 26 | a | Rhabditida; stoma with a protrusible stomatostyle; lip region simple; posterior esophageal region either a bulb without valve or overlapping glands | Tylenchina; Tylenchomorpha | |
| b | Rhabditida; stoma without teeth or with denticles; lip region simple; esophageal corpus without bulb; posterior bulb with valve | Tylenchina; Panagrolaimorpha | ||
| c | Rhabditida; stoma without teeth or with denticles; lip region with probolae; esophageal corpus without bulb; posterior bulb with valve | Tylenchina; Cephalobomorpha | ||
| d | Rhabditida; stoma with teeth; lip region simple; corpus with muscular metacorpus; no valve in posterior bulb | Rhabditina; Diplogasteromorpha | ||
| e | Rhabditida; stoma without teeth or with denticles; lip region simple; corpus with metacorpus; posterior bulb with valve | Rhabditina; Rhabditomorpha | ||
| f | Rhabditida; juveniles with cephalic hooks; multinucleate esophageal glands; parasites of animals | Spirurina |