Family: Oral nematodesmata not a ring around mouth, more prominent to side and rear of mouth; typically 3 long, large polykinetids in oral cavity; cytostome expands along postoral suture .
Genus: Postoral kineties usually to left of oral poykinetids (Illustrated Guide, 1985). Left edge is more curved than right edge; cytopharynx with numerous strong fibrils; ectoplasm with numerous fusiform trichocysts; macronucleus oval; one to several micronulei (Kudo, 1966).

RAPD tree of Frontonia (Tsukii, Jpn. J. Protozool., vol. 36, 2002)

F. leucas
Nnm-1 12 images μm 4-9 Mic. Matsumoto Nagano, 2001	Cos-2 13 images μm 3-7 Mic. Ichikawa Chiba, 2001	Cos-1 17 images μm 3-4 Mic. Ichikawa Chiba, 2001	Gmt-6 13 images μm 2-4 Mic. Tatebayashi Gunmma, 2001	Hsf-4 11 images μm Sanda Hyogo, 2001
SIR-24 6 images μm Iruma Saitama, 2002	Ckr-1 13 images μm 0 Mic. ?
F. vernalis & Frontonia sp.
Hsf-32 8 images μm Sanda Hyogo, 2001	Tms-1 17 images μm ? Mic. Tochigi,	Tms-2 10 images μm 1-2 Mic. Tochigi,
F. marina
Shm-1 16 images 158-185 x 53-72 μm 1-3 Mic. Mishima Shizuoka, 2001	40-1a 19 images μm 2-3 Mic. USA, 1999	D-5 15 images μm 1-2 Mic. Tokyo, 199?	Tna-1 13 images μm 1-2 Mic. Tochigi,
F. acuminata
Kgy-2 8 images μm 1 Mic. Yaku Island Kagoshima, 2001	Tou-1 9 images μm 1 Mic. Ujiie (Sakura) Tochigi, 2001
F. depressa
27-1B 4 images μm 1 Mic. Hiroshima, 199?

Similar Genus --> Disematostoma