Pleopods reduced to small bilobate or obscurely bilobate, setose plates with residual differentiation of pseudobranchial lobes, are among the main diagnostic characters of the genus Heteromysis. The monotypic subgenus Neoheteromysis Băcescu, 1976, is characterized by pleopods 2–4 modified by elongate, smooth setae in both sexes. Modifications of male pleopods by spines or by attenuated setae are typical of the subgenus Olivemysis Băcescu, 1968, where they show a great species-specific diversity related to nine different morphological constellations. Unexpectedly, all four new species of Olivemysis described below are quite unusual by demonstrating a total of three different, rare combinations of pleopods modified by spines. More common modifications are known in six insufficiently known species so far not assigned to any subgenus. Pleopods of both sexes are unmodified (as far as known) unless listed in the following (data from first descriptions of species; additional data sources given in square brackets):
MALE PLEOPODS 1, 3–4. H. (O.) cocoensis Price, Heard & Vargas, 2018.
MALE PLEOPODS 1–4. H. (O.) gomezi Băcescu, 1970; H. (O.) mayana Brattegard, 1970; H. (O.) smithsoniana sp. nov.
PLEOPODS 1–5 IN BOTH SEXES. H. (O.) mclellandi Price & Heard, 2011.
MALE PLEOPOD 2. H. (O.) dardani Wittmann, 2008 (in small adult males only); H. (O.) sixi sp. nov.
MALE PLEOPODS 2–4. H. (O.) dardani Wittmann, 2008 (in average-sized and large males); H. (O.) ekamako Wittmann & Chevaldonné, 2016; H. (O.) macrophthalma Băcescu, 1983; H. (O.) meenakshiae Bamber, 2000 (pleopod 4 unknown); H. (O.) quadrispinosa Murano, 1988; H. tattersalli H. Nouvel, 1942 [O.S. Tattersall 1967]; H. (O.) tenuispina Murano, 1988; H. (O.) wirtzi Wittmann, 2008; H. (O.) zeylanica W.M. Tattersall, 1922 [in material from Australia according to Murano 1988].
MALE PLEOPODS 2–4, FEMALE PLEOPOD 2. H. (O.) hornimani sp. nov.; H. (O.) waikikensis sp. nov.
PLEOPODS 2–4 IN BOTH SEXES. H. (N.) muelleri Băcescu, 1976.
MALE PLEOPODS 2–5, FEMALE PLEOPOD 2. H. (O.) kushimotensis Murano & Fukuoka, 2003.
MALE PLEOPODS 3–4. H. (O.) abrucei Băcescu, 1979; H. (O.) agelas Modlin, 1987; H. (O.) beetoni Modlin, 1984; H. (O.) coralina Modlin, 1987; H. digitata W.M. Tattersall, 1927 [O.S. Tattersall 1967]; H. (O.) domusmaris Wittmann & Abed-Navandi, 2019; H. (O.) essingtonensis Murano, 1988; H. (O.) guitarti Băcescu, 1968; H. (O.) kensleyi Modlin, 1987; H. (O.) mariani Băcescu, 1970; H. (O.) maxima Murano, 1998; H. (O.) modlini Price & Heard, 2011; H. odontops Walker, 1898 [O.S. Tattersall 1967]; H. panamaensis O.S. Tattersall, 1967; H. (O.) rubrocincta Băcescu, 1968; H. (O.) sabelliphila Wittmann & Wirtz, 2017; H. (O.) siciliseta Brattegard, 1970; H. singaporensis O.S. Tattersall, 1967; H. (O.) tuberculospina Modlin, 1987; H. (O.) zeylanica W.M. Tattersall, 1922 [in material from Indian Ocean according to O.S. Tattersall 1967 and Pillai 1968].
MALE PLEOPOD 4. H. (O.) actiniae Clarke, 1955 [Brattegard 1969]; H. (O.) bermudensis G.O. Sars, 1885 [Băcescu & Iliffe 1986]; H. (O.) ebanksae Price & Heard, 2008; H. (O.) floridensis Brattegard, 1969 [Modlin 1987]; H. (O.) xanthops Ii, 1964 [O.S. Tattersall 1967]. O.S. Tattersall (1967) claimed modified male pleopods 4 for H. gymnura W.M. Tattersall, 1922, but did not state whether she referred to the (meanwhile probably lost) types from the Gulf of Manaar (N Indian Ocean) or to non-types from Zanzibar.According to Wittmann (2013), materials from Zanzibar and Australia attributed to H. gymnura by O.S. Tattersall (1962, 1967) and Murano (1988), respectively, do not belong to this species.
Only females known in H. (O.) ningaloo Daneliya, 2012 and H. (O.) sexspinosa Murano, 1988, each without modified pleopods.
Among the here listed species, female pleopods were so far not described in H. abrucei, H. floridensis, H. gomezi, H. gymnura, H. maxima, H. odontops, H. panamaensis, H. sixi sp. nov., H. tattersalli, H. tenuispina, H. tuberculospina, and H. zeylanica.