| Ingroup |
| Placobdelloides sirikanchanae sp. nov. | Songkhla, Thailand | MK282428 | MK282433 |
| Songkhla, Thailand | MK282429 | MK282434 |
| Songkhla, Thailand | MK282430 | MK282435 |
| Songkhla, Thailand | MK282431 | MK282436 |
| Songkhla, Thailand | MK282432 | MK282437 |
| Placobdelloides jaegerskioeldi (Johansson, 1909) | Sudan, South Africa | AY962463 | AY962450 |
| Placobdelloides multistriatus (Johansson, 1909) | Louisiana, USA | DQ414338 | DQ414383 |
| Placobdelloides siamensis (Oka, 1917) | Bangkok, Thailand | AY962449 | AY962462 |
| Bangkok, Thailand | MH777415 | MH777409 |
| Bangkok, Thailand | MH777416 | MH777410 |
| Bangkok, Thailand | MH777417 | MH777411 |
| Bangkok, Thailand | MH777418 | MH777412 |
| Bangkok, Thailand | MH777419 | MH777413 |
| Bangkok, Thailand | MH777420 | MH777414 |
| Udon Thani, Thailand | MN221458 | MN242784 |
| Udon Thani, Thailand | MN221459 | MN242785 |
| Udon Thani, Thailand | MN221460 | MN242786 |
| Outgroup |
| Alboglossiphonia heteroclita (Linnaeus, 1761) | Michigan, USA | AF116016 | AY047339 |
| Alboglossiphonia quadrata (Moore, 1949) Sawyer, 1986 | Namibia, South Africa | AY962455 | AY962441 |
| Alboglossiphonia weberi (Blanchard, 1897b) | Hawaii, USA | AY962453 | AY962440 |
| Batracobdelloides tricarinata (Blanchard, 1897a) | Hoedspruit, South Africa | AY962457 | AY962445 |
| Glossiphonia baicalensis (Stchegolew, 1922) | Lake Baikal, Russia | AY047329 | AY047355 |
| Glossiphonia complanata (Linnaeus, 1758) | United Kingdom | MF458715 | AY047345 |
| Glossiphonia concolor (Apathy, 1888) | Kila River, Sweden | AY962458 | AY962446 |
| Glossiphonia elegans (Verrill, 1872) | Connecticut, USA | AY047322 | AY047335 |
| Glossiphonia verrucata (Mueller, 1844) | Rio s' Adde, Italy | AY962459 | AY962447 |
| Helobdella fusca (Castle, 1900) | Michigan, USA | AF329038 | AF329061 |
| Helobdella robusta (Shankland, Bissen & Weisblat, 1992) | Sacramento River, USA | MF067148 | MF067201 |
| Hemiclepsis marginata (Mueller, 1774) | Etang de la Musse, France | AF003259 | AY047336 |
| Hirudo medicinalis (Linnaeus, 1758) | Gotland, Sweden | HQ333517 | KU672396 |
| Marsupiobdella africana Goddard & Malan, 1912 | South Africa | AF116015 | AY047347 |
| Placobdella montifera (Moore, 1906) | Washington, USA | MF067129 | MF067212 |
| Placobdella pediculata (Hemingway, 1908) | Lake Pepin, USA | MF067121 | MF067222 |
| Theromyzon bifarium Oosthuizen & Davies, 1993 | North USA | AY047330 | AY047356 |
| Theromyzon tessulatum (Mueller, 1774) | Europe | AY047318 | AY047338 |