http://en.wikipedia.org/wiki/Ascidiacea
Ascidians are soft-bodied animals, and for this reason their fossil record is almost entirely lacking. The earliest reliable ascidians is Shankouclava shankouense from the Lower Cambrian Maotianshan Shale (South China).There are also two enigmatic species from the Ediacaran period with some affinity to the ascidians - Ausiafrom the Nama Group of Namibia and Burykhia from the Onega Peninsula, White Sea of northern Russia.They are also recorded from Lower Jurassic (Bonet and Benveniste-Velasquez, 1971; Buge and Monniot,1972) and the Tertiary from France (Deflandre-Riguard, 1949, 1956; Durand, 1952; Deflandre and Deflandre-Rigaud, 1956; Bouche, 1962; Lezaud, 1966; Monniot and Buge, 1971; Varol and Houghton, 1996). Older (Triassic) records are ambiguous.The representatives of the genus Cystodytes (family Polycitoridae) have been described from the Pliocene of France by Monniot (1970, 1971) and Deflandre-Rigaud (1956), and from Eocene of France by Monniot and Buge (1971), and lately from the Late Eocene of S Australia by Łukowiak (2012).
Ascidians are soft-bodied animals, and for this reason their fossil record is almost entirely lacking. The earliest reliable ascidians is Shankouclava shankouense from the Lower Cambrian Maotianshan Shale (South China).There are also two enigmatic species from the Ediacaran period with some affinity to the ascidians - Ausiafrom the Nama Group of Namibia and Burykhia from the Onega Peninsula, White Sea of northern Russia.They are also recorded from Lower Jurassic (Bonet and Benveniste-Velasquez, 1971; Buge and Monniot,1972) and the Tertiary from France (Deflandre-Riguard, 1949, 1956; Durand, 1952; Deflandre and Deflandre-Rigaud, 1956; Bouche, 1962; Lezaud, 1966; Monniot and Buge, 1971; Varol and Houghton, 1996). Older (Triassic) records are ambiguous.The representatives of the genus Cystodytes (family Polycitoridae) have been described from the Pliocene of France by Monniot (1970, 1971) and Deflandre-Rigaud (1956), and from Eocene of France by Monniot and Buge (1971), and lately from the Late Eocene of S Australia by Łukowiak (2012).
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