Gonyaulacysta eumorpha (Cookson and Eisenack, 1960) Sarjeant, 1966

Combination not validly published since Sarjeant, 1966, did not fully reference the basionym.
Now Leptodinium. Originally Gonyaulax, subsequently Gonyaulacysta (combination not validly published), thirdly (and now) Leptodinium.
Holotype: Cookson and Eisenack, 1960, pl.37, fig.1; Jan du Chêne et al., 1986, pl.75, fig.4
Locus typicus: Canning Basin, Australia
Stratum typicum: Late Jurassic

Original description: Cookson and Eisenack, 1960, p.246: Gonyaulax eumorpha
Shell rather large, ovoidal, flattened dorso-ventrally; epitheca broadly rounded, hypotheca narrowing somewhat towards the antapex. The girdle, which is equatorial, helicoid and broad, and the plates are bordered by thin, rather high ledges which may be perforated. The formula is 4", 6"", 5""", 1p, 1"""", but it seems that 6"" is very small and a long intercalary plate, the transverse boundary of which is indistinct, is developed on the ventral surface. Three of the four apical plates are always evident on the ventral surface.
Dimensions: Holotype: 112 Ám long, 110 Ám broad. Paratype: 98 Ám long, 93 Ám broad. Range: length 86-112 Ám, breadth 86-110 Ám.