Key to the valid pleioplanid species

1. Ejaculatory duct with a straight stylet and directed backwards …………………………………….2

– Ejaculatory duct unarmed, without stylet and directed backwards …………………………………8

– Ejaculatory duct with a spiral-shaped stylet (forming a loop between the prostatic vesicle and the pharynx) and directed forward ……………………………………………………………………11

2. Dorsal appearance translucent ………………………………………………………………………3

– Dorsal appearance opaque …………………………………………………………………………5

3. Spermiducal bulbs absent; body shape oval …………………… Pleioplana okusi Bulnes et al., 2009

– Spermiducal bulbs present; body shape elongated …………………………………………………4

4. Nuchal tentacles absent; tentacular knobs present; tentacular eyes in rounded and compact clusters in place of the tentacles; male copulatory apparatus not enclosed in a muscular bulb; Lang’s vesicle present ……………………………………………… Pleioplana delicata (Yeri & Kaburaki, 1918)

– Nuchal tentacles present; tentacular knobs absent; tentacular eyes at the base of or within the tentacles; male copulatory apparatus enclosed in a muscular bulb; Lang’s vesicle absent ……………………………………………………… Persica qeshmensis Maghsoudlou et al., 2015

5. Body shape elongated ………………………………………………………………………………6

– Body shape oval ……………………………………………………………………………………7

6. Pharynx located at the end of the first body third; spermiducal bulbs present; oral pore in the second body third and in the posterior region of the pharynx; male and female gonopores clearly separated ……………………………………………………………… Pleioplana atomata O.F. Müller, 1776

– Pharynx in the second or last body third; spermiducal bulbs absent; oral pore in the second body third and in the middle of the pharynx; male and female gonopores located in a common pore ………………………………………………………………… Pleioplana californica (Plehn, 1898)

7. Spermiducal bulbs absent; connection between ejaculatory duct and prostatic vesicle without projection …………………………………………………… Pleioplana mortenseni (Bock, 1913)

– Spermiducal bulbs present; connection between ejaculatory duct and prostatic vesicle with projection ……………………………… Pleioplana bosphorensis Bulnes, Kalkan & Karhan, 2009

8. Cerebral eyes absent; spermiducal bulbs present; vagina slanted towards the posterior end of the body……………………………………………………………………………………………9

– Cerebral eyes in two clusters; spermiducal bulbs absent; vagina looping towards the male complex … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … 1 0

9. Dorsal longitudinal median line not outstanding; oral pore in the second body third and in the middle of the pharynx …………………………… Izmira turkeyi Bulnes, Kalkan & Karhan, 2010

– Dorsal longitudinal median line highlighted by a concentration of spots; oral pore in the second body third and in the posterior region of the pharynx …………… Izmira cinari Bulnes, 2010

10. Male and female gonopores located very close to each other (in the same body third); connection between ejaculatory duct and prostatic vesicle with projection ………………… ………………………………………………………………… Melloplana japonica (Kato, 1937)

– Male and female gonopores clearly separated (in different body thirds); connection between ejaculatory duct and prostatic vesicle without projection ………………………………………… …………………………………………………………… Melloplana ferruginea (Schmarda, 1859)

11. Pharynx at the end of the first body third ………………… Laqueusplana bocki gen. et sp. nov.

– Pharynx in the second or last body third ……… Laqueusplana megala (Marcus, 1952) comb. nov.