Key to subfamilies of Cyclocoelidae Stossich, 1902

1a. Ovary forming a triangle with the testes.................................................................. 2

1b. Ovary nearly in a straight line with testes................................................................. 4

2a. Ovary intertesticular............................................................ Cyclocoelinae Stossich, 1902

2b. Ovary pretesticular or posttesticular...................................................................... 3

3a. Ovary pretesticular to opposite anterior testis...................................... Haematotrephinae Dollfus, 1948

3b. Ovary posttesticular or opposite posterior testis...................................... Szidatitreminae Dronen, 2007

4a. Ovary posttesticular........................................................ Ophthalmophaginae Harrah, 1922

4b. Ovary intertesticular................................................................................... 5

5a. Testes tandem to nearly tandem.................................................... Hyptiasminae Dollfus, 1948

5b. Testes nearly side by side..................................................... Skrjabinocoelinae Dronen, 2007