Female- Head offset, lips higher than in A. solitaire, rounded, the anterior portion not offset.  Anterior end of esophageal expansion tapering toward isthmus, the two portions of the esophagus not abutting.  Esophageal constriction located at 30 to 38% of esophageal length from anterior end of body.  Muscle bands of esophageal sheath straight, not spiral.  Cardia 19u long in holotype, 21 to 25u long in other females, slightly over twice as long as its diameter. Cuticle about 1u thick, sub-cuticle slightly thinner at mid-body.  Vulva circular on surface, vaginal lumen gradually becoming diamond-shaped, then cross-shaped, within body.  Vaginal cuticularization in two parts, ventral part disc like, dorsal part less heavily striated, hemispherical in lateral view, of the same diameter as sphincter.  Anterior gonad wide throughout its length except for constriction near vulva, its terminus truncate, containing sperm cells in proximal part or throughout its length.  Posterior uterus wide proximally, constricted to a narrow sinuous portion distally, sperm present within it.  Tail conical, ventral side not curved as much as dorsal side, terminus rounded.  A pair of caudal pores present on each side of tail; in one specimen they are paired on one side, nearly in the same row with the anterior lateral pores on the other.  Lateral pores anterior to anus in a single row.  Organs of the lateral chord associated with the pores large and conspicuous.  Prerectum about 6 times as long as anal body diameter in holotype, 5 times as long in one paratype, stricture not visible in remaining specimens.
Male- Anterior portion of body similar to that of females.  Tail slightly curved ventrally, curved more dorsally to a rounded terminus.  Three caudal pores present on each side of tail, lateral pores staggered between anus and anterior supplement, in a single row anterior to supplements.  Ventromedian supplements 14 in allotype, 13 to 15 in paratypes, contiguous, beginning anterior to spicule.
Diagnosis- A. thornei is very similar to both A. choristum and A. solitaire.  In A. thornei the female tail tends to be more tapered and the terminus is not quite as broad as in A. solitaire.  There is more curvature dorsally and less ventally than in A. solitaire; thus the terminus has a slightly more ventral location in A. thornei.  The female tail of A. choristum is wider in comparison to its length than in A. thornei, and the terminus is slightly broader.  The subcuticle at mid-body is somewhat thicker than the outer cuticle in A. choristum, whereas in the other two species both cuticular layers at mid-body are of nearly the same thickness.  There are 12 to 15 ventral supplements on the male of A. thornei and 19 to 26 in A. choristum.  The stylet of A. thornei is slightly shorter than the stylet in either A. choristum or A. solitaire, and the spicules are shorter in A. thornei than in A. choristum.
Type locality and habitat- Soil around roots of Balsamorrhiza sagitata, Cache County, Utah.
(Description- Hechler, 1969)