Valvaeodinium wapellense (Pocock, 1972) Below, 1987; Emendation: Dörhöfer and Davies, 1980, p.23, as Dapcodinium wapellense.

Now Opaeopsomus. Originally (and now) Opaeopsomus, subsequently Dapcodinium, thirdly Valvaeodinium.
Lentin and Williams (1993, p.465) retained this species in Opaeopsomus.
Lentin and Williams (1993, p.465) recommended that this name be restricted to the type.

Holotype: Pocock, 1972, pl.24, fig.14
Locus typicus: Western Canada
Stratum typicum: Callovian

Original descrpition: Pocock, 1972, p.97: Opaeopsomus wappelensis
Vesicle ellipsoidal to sphaerical; epitheca and hypotheca hemipshaerical; no apical or antapical processes developed; transverse furrow well delineated; parallel sided; helicoidal, 6µm wide, longitudinal furrow only faintly visible over part of its lengh. archaeopyle apical with free simple operculum; vesicle two-layered, casule smooth; about 5µm thick; tightly appressed to outer layer; sutures reflected by narrow raised ridges, 4µm high and less than 0.25µm wide; accessory ridges developed in addition to the sutural ridges; making determination of tabulation impossible; brocci of reticulum resulting from intersection of ridges, rounded and very variable in size; 1.0 x 5.0µm wide; thin membrane developed completely enveloping the vesicle and supported by the ridges; colorless to pale yellow; size range 42.9 - 45.0 x 39.6 - 43µm.

Emended diagnosis: Dörhöfer and Davies, 1980: Dapcodinium wapellense
Proximate dinoflagellate cysts with circular ambitus and slight apical horn. Tabulation expressed by sutural crests, surface otherwise smooth. Tabulation 4", 5a, 7", 7c, 7""", 4p, 1"""", 5s. Disintegration archeopyle, 4A + 5l + 7P initiating at 2a.

Affinities:
Pocock, 1972, p.97: Differs from Fovilarnax in posessing transverse and longitudinal furrows, thus indicating definite dinoflagellate affinity.