• Posidonia Bronn, 1828 †
• Posidonia König, 1805
• Posidonia (Karadjalia) Sadykov, 1962 † accepted as Guerichia Rzehak, 1910 †
• Posidonia (Karadjalia) bairensis Sadykov, 1962 † accepted as Guerichia bairensis (Sadykov, 1962) †
• Posidonia (Karadjalia) kazakhstanensis Sadykov, 1962 † accepted as Guerichia kazakhstanensis (Sadykov, 1962) †
• Posidonia (Karadjalia) mariannae (B. I. Chernyshev, 1941) † accepted as Guerichia mariannae (B. I. Chernyshev, 1941) †
• Posidonia (Karadjalia) mariannae var. hemicyclia Sadykov, 1962 † (unaccepted > unavailable name)
• Posidonia (Karadjalia) nalivkini Sadykov, 1962 † accepted as Guerichia nalivkini (Sadykov, 1962) †
• Posidonia (Karadjalia) ovata Sadykov, 1962 † accepted as Guerichia ovata (Sadykov, 1962) †
• Posidonia (Karadjalia) simorini Sadykov, 1962 † accepted as Guerichia simorini (Sadykov, 1962) †
• Posidonia (Karadjalia) simorini var. keregatasensis Sadykov, 1962 † (unaccepted > unavailable name)
• Posidonia (Karadjalia) venusta (Münster, 1840) † accepted as Guerichia venusta (Münster, 1840) †
• Posidonia (Karadjalia) venustiformis Sadykov, 1962 † accepted as Guerichia venustiformis (Sadykov, 1962) †
• Posidonia (Karadjalia) venustiformis var. globosa Sadykov, 1962 † (unaccepted > unavailable name)
• Posidonia (Posidonia) Bronn, 1828 † represented as Posidonia Bronn, 1828 †
• Posidonia (Posidonia) kavuni Sadykov, 1962 † (uncertain > unassessed)
• Posidonia (Posidonia) orbicularis Sadykov, 1962 † (uncertain > unassessed)
• Posidonia (Posidonia) protobecheri Sadykov, 1962 † (uncertain > unassessed)
• Posidonia (Posidonia) protobecheri var. djailmensis Sadykov, 1962 † (unaccepted > unavailable name)
• Posidonia (Posidonia) protobecheri var. nuraensis Sadykov, 1962 † (unaccepted > unavailable name)
• Posidonia (Posidonia) striata Sadykov, 1962 † (uncertain > unassessed)
• Posidonia (Posidonia) striata var. longa Sadykov, 1962 † (unaccepted > unavailable name)
• Posidonia aequilatera Vukhuc, 1965 † (uncertain > unassessed)
• Posidonia alveata Conrad, 1841 † accepted as Grammysioidea alveata (Conrad, 1841) †
• Posidonia angustifolia Cambridge & Kuo, 1979
• Posidonia anomala Münster, 1835 † (uncertain > unassessed)
• Posidonia arcuata Conrad, 1841 † accepted as Grammysioidea arcuata (Conrad, 1841) †
• Posidonia australis J.D.Hooker, 1858
• Posidonia becheri Bronn, 1828 † (uncertain > unassessed)
• Posidonia bronnii Zieten, 1833 † (uncertain > unassessed)
• Posidonia bronnii var. elongata Goldfuss, 1835 † (uncertain > unassessed)
• Posidonia buchii Roemer, 1836 † accepted as Bositra buchii (Roemer, 1836) †
• Posidonia canaliculata Goldfuss, 1835 † (uncertain > unassessed)
• Posidonia caulinii K.D.Koenig, 1805 accepted as Posidonia oceanica (Linnaeus) Delile, 1813
• Posidonia coriacea Cambridge & Kuo accepted as Posidonia ostenfeldii Hartog, 1970
• Posidonia denhartogii Kuo & Cambridge, 1984
• Posidonia gigantea Münster, 1835 † (uncertain > unassessed)
• Posidonia hians (Waldschmidt, 1885) † accepted as Pterochaenia insidiosa (Barrande, 1881) †
• Posidonia kirkmanii J.Kuo & Cambridge, 1984
• Posidonia lata Betekhtina, 1979 † (accepted > unreplaced junior homonym)
• Posidonia lirata Conrad, 1838 † accepted as Paracyclas lirata (Conrad, 1838) †
• Posidonia marcellensis J. M. Clarke, 1904 † accepted as Pterochaenia marcellensis (J. M. Clarke, 1904) †
• Posidonia mariannae B. I. Chernyshev, 1941 † accepted as Guerichia mariannae (B. I. Chernyshev, 1941) †
• Posidonia mimer Öberg, 1877 † accepted as Peribositria mimer (Öberg, 1877) †
• Posidonia minuta Zieten, 1833 † accepted as Euestheria minuta (Zieten, 1833) †
• Posidonia oceanica (Linnaeus) Delile, 1813
• Posidonia orbicularis Münster, 1835 † (uncertain > unassessed)
• Posidonia ornati Quenstedt, 1851 † accepted as Bositra ornati (Quenstedt, 1851) †
• Posidonia ostenfeldii Hartog, 1970
• Posidonia pannonica (Mojsisovics, 1873) † accepted as Peribositria pannonica (Mojsisovics, 1873) †
• Posidonia paradoxica J.-H. Li, 1982 † (uncertain > unassessed)
• Posidonia qijiagouensis Z.-R. Yang, 1983 † (uncertain > unassessed)
• Posidonia radiata Goldfuss, 1835 † (uncertain > unassessed)
• Posidonia robertsoniae Kuo & Cambridge, 1984 accepted as Posidonia ostenfeldii Hartog, 1970
• Posidonia serrulata (R.Br.) Spreng. accepted as Oceana serrulata (R.Brown) Byng & Christenh.
• Posidonia sinuosa Cambridge & Kuo, 1979
• Posidonia socialis Münster, 1835 † (uncertain > unassessed)
• Posidonia somaliensis L. R. Cox, 1935 † accepted as Bositra buchii (Roemer, 1836) †
• Posidonia tamugangensis Z.-R. Yang, 1983 † (uncertain > unassessed)
• Posidonia wuweiensis J.-H. Li, 1982 † (uncertain > unassessed)
• Posidonia yinkengensis J.-H. Li, 1982 † (uncertain > unassessed)
• Posidoniaceae Vines