Back
Trithyrodinium suspectum
Trithyrodinium suspectum (Manum and Cookson, 1964) Davey, 1969
Originally Hexagonifera, subsequently (and now) Trithyrodinium, thirdly Deflandrea. Lentin and Williams (1976, p.100) retained this species in Trithyrodinium.
Holotype: Manum and Cookson 1964, pl.1, fig.9
Locus typicus: Graham Islands, Arctic Canada
Stratum typicum: Cenomanian
--------------------------------------------------
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Trithyrodinium suspectum (Manum and Cookson, 1964) Davey, 1969b. Trithyrodinium suspectum has 2-4 µm endophragm with the thicker luxuria being composed of rod shaped elements or unequal length and with small widely spaced warts on the surface. Endoarcheopyle 3I. Periphragm delicate, thin, with blunt apical and two smaller antapical horns. Suggestion of cingulum. Size: Overall 91-118 µ, endocyst 65-78 µm.
--------------------------------------------------
Original description: Manum and Cookson, 1964, p. 9-10: Hexagonifera suspecta
Shell circular in outline, wall 2.5-4.0 Ám thick, twolayered, dotted in surface view, unevenly wavy in optical section due to the thicker outer layer being composed of rod-shaped elements of unequal length. In addition, small, widely spaced warts sometimes occur on the surface. The shell opens somewhat obliquely at one end by the removal of three portions of the wall the median one of which is hexagonal with alternating short and long sides and the ones on either side of it roughly pentagonal. Usually the shell is partially and sometimes entirely enveloped in a delicate, closely opposed, hyaline membrane. When entire, the membrane has a blunt apical horn and two smaller antapical horns. Slight lateral indentations in the membrane suggest the presence of an equatorial girdle.
Dimensions: Holotype: shell diameter 73 Ám, overall length including the horns 118 Ám. Range: shell diameter 65-78 Ám, overall length of three horned specimens 91 Ám, 92 Ám, and 97 Ám respectively.
Affinities:
Manum and Cookson, 1964, p. 10: Hexagonifera suspecta
The three species of Hexagonifera previously known (Cookson & Eisenack 1961, 1962) have been mainly distinguished by the ornamentation of the shell. In H. glabra the wall is smooth, in H. vermiculata the pattern is vermiculate to reticulate, and in H. chlamydata verrucose. The ornament of H. suspecta differs from that of all three species in resulting from closely arranged rods which in surface view appear as small dots. These dots are much finer than the irregular spots of H. chlamydata. The closeness of the outer membrane to the wall of the shell parallels that in H. glabra and H. vermiculata in both of which portions of the membrane may adhere to the shell. The possession of horns in species of Hexagonifera has not been previously observed.
The general appearance of the horned specimens is strikingly like that of some species of Deflandrea, e. g. D. phosphoritica Eis. Furthermore, the mode of opening is exactly similar to that occurring in the capsules of D. granulifera and D. verrucosa Manum (1963) of which illustrations are included here for comparison (pl. 1, figs. 7, 8). A similar mode of opening is seen in D. thomasi (cp. pl. 1, fig. 6).
The spximens of H. suspecta with an entire outer membrane throw light on the morphology of the genus Hexagonifera (cp. Cookson & Eisenack 1962 p. 495). They indicate that the outer thin membrane which sometimes is present in its entirety, but usually is partly or completely detached, corresponds to the theca of forms like Deflandrea. In fact the resemblance which such specimens of Hexagonifera stuipecta bear to Defandrea indicates that a definite relationship exists between the two genera. It is for this reason that we have placed Hexagonifera togethcr with Deflandrea under Peridiniaceae.
Originally Hexagonifera, subsequently (and now) Trithyrodinium, thirdly Deflandrea. Lentin and Williams (1976, p.100) retained this species in Trithyrodinium.
Holotype: Manum and Cookson 1964, pl.1, fig.9
Locus typicus: Graham Islands, Arctic Canada
Stratum typicum: Cenomanian
--------------------------------------------------
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Trithyrodinium suspectum (Manum and Cookson, 1964) Davey, 1969b. Trithyrodinium suspectum has 2-4 µm endophragm with the thicker luxuria being composed of rod shaped elements or unequal length and with small widely spaced warts on the surface. Endoarcheopyle 3I. Periphragm delicate, thin, with blunt apical and two smaller antapical horns. Suggestion of cingulum. Size: Overall 91-118 µ, endocyst 65-78 µm.
--------------------------------------------------
Original description: Manum and Cookson, 1964, p. 9-10: Hexagonifera suspecta
Shell circular in outline, wall 2.5-4.0 Ám thick, twolayered, dotted in surface view, unevenly wavy in optical section due to the thicker outer layer being composed of rod-shaped elements of unequal length. In addition, small, widely spaced warts sometimes occur on the surface. The shell opens somewhat obliquely at one end by the removal of three portions of the wall the median one of which is hexagonal with alternating short and long sides and the ones on either side of it roughly pentagonal. Usually the shell is partially and sometimes entirely enveloped in a delicate, closely opposed, hyaline membrane. When entire, the membrane has a blunt apical horn and two smaller antapical horns. Slight lateral indentations in the membrane suggest the presence of an equatorial girdle.
Dimensions: Holotype: shell diameter 73 Ám, overall length including the horns 118 Ám. Range: shell diameter 65-78 Ám, overall length of three horned specimens 91 Ám, 92 Ám, and 97 Ám respectively.
Affinities:
Manum and Cookson, 1964, p. 10: Hexagonifera suspecta
The three species of Hexagonifera previously known (Cookson & Eisenack 1961, 1962) have been mainly distinguished by the ornamentation of the shell. In H. glabra the wall is smooth, in H. vermiculata the pattern is vermiculate to reticulate, and in H. chlamydata verrucose. The ornament of H. suspecta differs from that of all three species in resulting from closely arranged rods which in surface view appear as small dots. These dots are much finer than the irregular spots of H. chlamydata. The closeness of the outer membrane to the wall of the shell parallels that in H. glabra and H. vermiculata in both of which portions of the membrane may adhere to the shell. The possession of horns in species of Hexagonifera has not been previously observed.
The general appearance of the horned specimens is strikingly like that of some species of Deflandrea, e. g. D. phosphoritica Eis. Furthermore, the mode of opening is exactly similar to that occurring in the capsules of D. granulifera and D. verrucosa Manum (1963) of which illustrations are included here for comparison (pl. 1, figs. 7, 8). A similar mode of opening is seen in D. thomasi (cp. pl. 1, fig. 6).
The spximens of H. suspecta with an entire outer membrane throw light on the morphology of the genus Hexagonifera (cp. Cookson & Eisenack 1962 p. 495). They indicate that the outer thin membrane which sometimes is present in its entirety, but usually is partly or completely detached, corresponds to the theca of forms like Deflandrea. In fact the resemblance which such specimens of Hexagonifera stuipecta bear to Defandrea indicates that a definite relationship exists between the two genera. It is for this reason that we have placed Hexagonifera togethcr with Deflandrea under Peridiniaceae.