Spinidinium rhombicum (Cookson and Eisenack, 1974) Stover and Evitt, 1978

Now Spinidinium echinoideum ssp. rhombicum. Originally Deflandrea rhombica, subsequently (and now) Spinidinium echinoideum ssp. rhombicum, thirdly Spinidinium rhombicum. Lentin and Williams, 1981 retained this taxon as a subspecies of Spinidinium echinoideum (Cookson and Eisenack, 1960) Lentin and
Williams, 1976.
Holotype: Cookson and Eisenack, 1974, pl.20, fig.7
Locus typicus: Perth Basin, Australia
Stratum typicum: Albian-Cenomanian

Original diagnosis: Cookson and Eisenack, 1974, p. 49: Deflandrea rhombica
Overall shape rhombic. Periphragm flattened, epicyst triangular with slightly concave to convex flanks. Weakly developed, blunt apical horn. Hypocyst triangular with pointed antapical horn. Hypocyst trapezoidal when second, weakly developed antapical horn present. Usually just one, pointed to thorn-like antapical horn present, which may be displaced towards the girdle. Girdle relatively wide but indistinct. Periphragm with short, pointed spines, strongest developed on girdle folds. Apex with few (2-4) diverging folds. Endophragm circular and clearly distinguished from the periphragm. Archaeopyle usually present, trapezoidal to rounded triangular.
Dimensions: Holotype c. 72-50 µm, range - length 57-90 µm, breadth 38-76 µm; length/breadth ratio 1,4 - 1,6:1.