Key to species of Astiotrema Looss, 1900 (sensu stricto)

1a. Cecal ends either not reaching significantly into or do not exceed testicular zone.................................. 2.

1b. Cecal ends extending deeply into post-testicular zone....................................................... 5.

2a. Cecal ends and posterior vitellarium extent exceed level of anterior testis; parasitize non-amphibian hosts.............. 3.

2b. Cecal ends and posterior vitellarium extent do not exceed level of anterior testis; parasitize amphibian hosts........................................................ Astiotrema ranarum (Mehra & Negi, 1926) Fotedar, 1971 (Figs. 12–14).

3a. Anterior extent of vitellarium does not exceed bifurcal level; ovary distant from ventral sucker and closer to anterior testis.................................................................................................... 4.

3b. Anterior extent of vitellarium pre-bifurcal and can reach to pharyngeal level; ovary contiguous with or very close to ventral sucker and more distant from anterior testis............... Astiotrema impletum (Looss, 1899) Looss, 1900 (Figs. 6–11).

4a. Anterior extent of vitellarium bifurcal; oral sucker distinctly larger than ventral sucker; parasitizes marine turtles........................................... Astiotrema karachiensis Bilqees, Khatoon & Khan, 2002 n. comb. (Figs. 26 & 27).

4b. Anterior extent of vitellarium post-bifurcal; suckers roughly equal in size; parasitizes freshwater turtles and fish...................................................................... Astiotrema odhneri Bhalerao, 1936 (Figs. 17–20).

5a. Anterior extent of vitellarium pre-ovarian but does not reach pre-bifurcal level, posterior extent terminates anterior to cecal ends.............................................................................................. 6.

5b. Anterior extent of vitellarium pre-bifurcal, posterior extent terminates at cecal ends or slightly further posteriorly........................................................................ Astiotrema fotedari Dhar, 1977 (Figs. 23–25).

6a. Genital pore immediately anterior to ventral sucker; ventral sucker relatively close to intestinal bifurcation............. 7.

6b. Genital pore anterior to ventral sucker by a distinct distance; ventral sucker distant from intestinal bifurcation...................................................................... Astiotrema cyclemysi Siddiqi, 1965 (Figs. 21 & 22).

7a. Esophagus distinct, long; anterior extent of vitellarium does not reach anterior to ventral sucker; ovary smaller than testes.......................................... Astiotrema reniferum (Looss, 1898) Looss, 1900 [type species] (Figs. 1–5).

7b. Esophagus indistinct or very short; anterior extent of vitellarium reaches anterior to ventral sucker and is confluent medially in pre-acetabular region; ovary and testes roughly equal in size........... Astiotrema emydis Ejsmont, 1930 (Figs. 15 & 16).