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Diacanthum tenuiceras
Diacanthum tenuiceras (Eisenack, 1958) Stover and Evitt, 1978; Emendations: Sarjeant, 1985a, p.63,65-66, as Acanthaulax? tenuiceras; Jan du Chêne et al., 1986b, p.29-30, as Tehamadinium tenuiceras.
Now Acanthaulax?. Originally Gonyaulax, subsequently Gonyaulacysta?, thirdly Diacanthum, fourthly Occisucysta, fifthly (and now) Acanthaulax?, sixthly Tehamadinium.
Below, 1981, transferred this species to Occisucysta Gitmez, 1970. Lentin and Williams, 1981, retained it in Diacanthum.
Holotype: Eisenack, 1958, pl.21, fig.15; Sarjeant, 1985, pl.6, figs.1-2; text-fig.3; Jan du Chêne et al., 1986(1), pl.118, fig.1; and Jan du Chêne et al., 1986(2), pl.24, fig.5.
Locus typicus: borehole at Marne, Feld Heide, N Germany
Stratum typicum: Late Barremian-Aptian
Translation Eisenack, 1958: Sarjeant, 1985, p.63
Original diagnosis: Eisenack, 1958, p.390: Gonyaulax tenuiceras
Shell thick-walled (consequently almost always dark brown), oval to almost spherical, epitheca and hypotheca usually almost equally large; transverse furrow spiral, always clear, bounded by low but stout crests. Horn straight, usually sharply developed, not tapering, appearing rectangular, apically expanding into a "crownlet". Plate boundaries formed by low crests. Plates and in particular their boundary crests ornamented with + numerous and densely set lamellate spinelets, short, sometimes stout, often delicate however, the lateral lamellae of which may grow together to form a flange, which is especially prominent in the median plane. Pylome not rare, broader than high.
Emended diagnosis: Sarjeant, 1985, p. 63, 65-66: Acanthaulax tenuiceras
Proximate, cornucavate, holotabulate cysts of moderate size, rotundly ovoidal. Epitract and hypotract of almost equal size and shape. A short apical horn, parallel-sided and blunt, is formed from periphragm only; the crests bounding the preapical paraplates impart to it a briefly furcate aspect. Paraplate boundaries marked by broad, low crests, echinate, with spines close set and of relatively uniform length; the spinelets in gonal situations may be slightly larger than those in other positions. Surface of phragma densely set with fine spinelets.
Paratabulation 2pr, 4", 6", 6c, 6""", 1p, 1pv, 2"""", 7s. Paraplate 4" is almost quadrate, having a moderately long boundary with a reduced 6"; the boundary between these paraplates intersects that of 1" in a position anterior to the junction of 1" with the sulcus. Paraplate 1""" is small and quadrate, 1p much larger. The sulcus is short and broad, divided into a large anterior, four small median and two elongate posterior paraplates. Paraplate lpv is the most ventrally situated of three paraplates occupying the antapical region: 1"""" and 2"""" are somewhat larger and are similar to each other in size and shape. Mode of archaeopyle formation not determined.
Dimensions: Holotype: overall length 74 Ám, breadth 62 Ám, length of horn 7 Ám, breadth of cingulum 4--5 Ám. Range of dimensions, as quoted by Eisenack: length around 60--83 Ám (mean 63 Ám), breadth 50--70 Ám (mean 60 Ám), 30 specimens having been measured.
Now Acanthaulax?. Originally Gonyaulax, subsequently Gonyaulacysta?, thirdly Diacanthum, fourthly Occisucysta, fifthly (and now) Acanthaulax?, sixthly Tehamadinium.
Below, 1981, transferred this species to Occisucysta Gitmez, 1970. Lentin and Williams, 1981, retained it in Diacanthum.
Holotype: Eisenack, 1958, pl.21, fig.15; Sarjeant, 1985, pl.6, figs.1-2; text-fig.3; Jan du Chêne et al., 1986(1), pl.118, fig.1; and Jan du Chêne et al., 1986(2), pl.24, fig.5.
Locus typicus: borehole at Marne, Feld Heide, N Germany
Stratum typicum: Late Barremian-Aptian
Translation Eisenack, 1958: Sarjeant, 1985, p.63
Original diagnosis: Eisenack, 1958, p.390: Gonyaulax tenuiceras
Shell thick-walled (consequently almost always dark brown), oval to almost spherical, epitheca and hypotheca usually almost equally large; transverse furrow spiral, always clear, bounded by low but stout crests. Horn straight, usually sharply developed, not tapering, appearing rectangular, apically expanding into a "crownlet". Plate boundaries formed by low crests. Plates and in particular their boundary crests ornamented with + numerous and densely set lamellate spinelets, short, sometimes stout, often delicate however, the lateral lamellae of which may grow together to form a flange, which is especially prominent in the median plane. Pylome not rare, broader than high.
Emended diagnosis: Sarjeant, 1985, p. 63, 65-66: Acanthaulax tenuiceras
Proximate, cornucavate, holotabulate cysts of moderate size, rotundly ovoidal. Epitract and hypotract of almost equal size and shape. A short apical horn, parallel-sided and blunt, is formed from periphragm only; the crests bounding the preapical paraplates impart to it a briefly furcate aspect. Paraplate boundaries marked by broad, low crests, echinate, with spines close set and of relatively uniform length; the spinelets in gonal situations may be slightly larger than those in other positions. Surface of phragma densely set with fine spinelets.
Paratabulation 2pr, 4", 6", 6c, 6""", 1p, 1pv, 2"""", 7s. Paraplate 4" is almost quadrate, having a moderately long boundary with a reduced 6"; the boundary between these paraplates intersects that of 1" in a position anterior to the junction of 1" with the sulcus. Paraplate 1""" is small and quadrate, 1p much larger. The sulcus is short and broad, divided into a large anterior, four small median and two elongate posterior paraplates. Paraplate lpv is the most ventrally situated of three paraplates occupying the antapical region: 1"""" and 2"""" are somewhat larger and are similar to each other in size and shape. Mode of archaeopyle formation not determined.
Dimensions: Holotype: overall length 74 Ám, breadth 62 Ám, length of horn 7 Ám, breadth of cingulum 4--5 Ám. Range of dimensions, as quoted by Eisenack: length around 60--83 Ám (mean 63 Ám), breadth 50--70 Ám (mean 60 Ám), 30 specimens having been measured.