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Mikrocysta bjaerkei
Mikrocysta bjaerkei Below, 1987
Holotype: Below, 1987, pl. 2, fig. 1-2, 4
Stratum typicum: Toarcian
Locus typicus: Knerten Hill near DeGeerdalen, Spitsbergen
Translation Below, 1987: Secretary of State, Canada, Translation Bureau
Original description: Below, 1987, p. 14-16.
Diagnosis (annotated): Arrangement of vesicles/plates on the dinoflagellate amphiesma PR, 5", 3a, 7"", 7c, 6""", 2"""", as, FM subdivided into several periflagellar platelets, ls, rs, ps; pentogonal 1"""" and hexagonal 2"""" partiform; omegaform ps very large. Cyst habit proximate, acavate, ovaloidal to polyhedral, epicyst transversely semi-ellipsoidal, apically rounded, somewhat smaller than the semi-ovoidal hypocyst with rounded antapex; size small; wall composed of pedium and spongy luxuria, surface rugulate, areate, the surface of the area homologous to an overlapping plate raised above the area homologous to the overlapped plate sloping down towards it at a sharp gradient along the finis, overlapping margins sometimes edged by coarse rugulae; areation formula NR PR/XPR, NR"/5", 3a, 7"", 7c, 6""", 2"""", as, FM, ls, rs, ps; PR undifferentiated or not reflected; 5 very small apicals, VI 1" (V) with porichnion on finis 1"/5", deltaform inverse-camerate 2" (VL), IV- nE 3" (L), IV-nE 4" (R), deltaform inverse-camerate 5" (VR); 3 small anterior intercalaries, deltaform inverse-camerate 1a (DL), deltaform linteloid or VII 2a (D), deltaform inverse-camerate 3a (R); 7 precingulars, anteriorly geniculate V-nE 1"" (VVL), anteriorly geniculate V-nE 2"" (L), anteriorly geniculate V-nE 3"" (DL), anteriorly linear IV-nE 4"" (D), anteriorly geniculate V-nE 5"" (DR), anteriorly geniculate V-nE 6"" (RVR), small anteriorly geniculate V-nE 7"" (VVR); cingulum helicoid laevorotatory, indented, heptaareate with lati 1c to 6c and fastigiate 7c; 6 postcingulars, posteriorly linear V-nE 1""" (VVL), posteriorly linear IV-nE 2""" (VL), posteriorly geniculate V-nE 3""" (DL), posteriorly linear IV-nE 4""" (D), posteriorly linear IV-nE 5""" (RDR), posteriorly linear V-nE 6 """ (VR); 2 antapicals partiform, V 1"""" descending towards LVL, VI 2"""" towards R; hypocystal sulcus indented, comprising V as, FM, small caroidal rs and ls, and large, omegaform VI ps; archeopyle apical, amplificate, 2" + 3"; operculum solvate, secate, general opercular formula 2"s + 3"s.
Dimensions of holotype: Length, 30 Ám, breadth, 27 Ám, thickness 27 Ám.
Remarks: This species is extraordinarily interesting because of the reflection of thecal-plate growth structures. On most specimens, the overlapping system is directly readable almost in full, and it is shown on the areation diagram (Figure 3). As can be demonstrated also for taxa of the tribe Phanerodinieae, usually 4""" is the culmen of the primtegulate hypocystal overlap series, but specimens with 3""" as culmen were also observed (Plate 2, fig. 11, 13). The ridge-tile areae are very prominent. At the fines bordering the areae reflecting the overlapped plates, they descend abruptly to the normal level of the cyst surface. The area reflecting the overlapped plate is often structured like a ramp. From the margin where its homologous plate was overlapped, its surface rises uniformly to the margin where the corresponding plate, in turn, overlapped its neighbor. There it stands out like the ridge-tile area. This arrangement, which is reminiscent of a paddle wheel, is seen most clearly in a polar aspect of the cyst (Plate 2, Fig. 11, 12 and 15). In addition, the overlapping margins frequently are edged by coarse rugulae. Perhaps these rugulate fringes on the areae reflect zones of increment on thecal plates. In that case, growth and overlapping would be correlated as in the Gonyaulax type of thecal-plate growth. If we use the character of overlapping areae descending like steps towards the overlapped areae to reconstruct the overlapping at the cingulum as well, then the transverse furrow on the theca was overlapped by precingular and by postcingular plates. The level of overlap is lower on the precingular side than on the postcingular. An important, albeit seldom illustrated detail of the areation is the porichnion on finis 1"/5". It may permit us to homologize area 5" of Mikrocysta with 4" of taxa of the tribe Phanerodinieae (see p. 13). As a rule, the surface between 1", the anterior intercalaries, 2", and 5" is undivided, as in Mikrocysta erugata, so that there appear to be only four apical areae in all. However, specimen S2- 805(KO-1)1/1 (Plate 2, Fig. 15) shows schematic relicts of two low circles of ribs in a peniareate position, which represent 3" and 4". In contrast to Mikrocysta erugata, only three anterior intercualries are discernible. The additional, minute trigonal area (2a anterior to 3"" in Mikrocysta erugata) was either not originally present on the theca, or not reflected, or reflected inadequately. Possibly the surfaces of the corresponding thecal plates were too small to be reflected as areae, so that they were reflected only by ornaments (thus, e.g., cop is often reflected by a granule, verruca, or baculum), which however, are no longer visible among the coarsely rugulate surface ornamentation of this species. The configuration of areae is: PR (1", 2", 3", 4", 5"), 1" (as, 1"", 2", PR, 5", 7""), 2" (PR, 1", 1"", 2"", 1a, 3"), 3" (PR, 2", 1a, 2a, 4a), 4" (PR, 3", 2a, 3a, 5"), 5" ( PR, 4", 3a, 6"", 7"", 1"), 1a (2"", 3"", 2a, 3", 2"), 2a (3"", 4"", 5"", 3a, 4", 3", 1a), 3a (5"", 6"", 5", 4", 2a), 1"" (c, 2"", 2", 1", as), 2"" (c, 3"", 1a, 2", 1""), 3"" (c, 4"", 2a, 1a, 2""), 4"" (c, 5"", 2a, 3""), 5"" (c, 6"", 3a, 2a, 4""), 6"" (c, 7"", 5", 3a, 5""), 7"" (c, as, 1", 5", 6""), as (1", 7"", c, FM, c, 1""), 1""" (c, s, 1"""", 2"""), 2""" (c, 1""", 1"""", 3"""), 3""" (c, 2""", 1"""", 2"""", 4"""), 4""" (c, 3""", 2"""", 5"""), 5""" (c, 4""", 2"""", 6"""), 6""" (c, 5""", 2"""", s), 1"""" (1""", 2""", 3""", 2"""", s), 2"""" (1"""", 3""", 4""", 5""", 6""", s).
The surface bears rugulae usually very tightly coiled liked intestines. They may be bevelled (Plate 2, Fig. 7, 8, 9, 11, 12, and 14) or reduced to granules (Plate 3, Fig. 4) or completely absent on intraareate surfaces. Figures 1-6 on Plate 3 show another variant of this species. The ramp-like structure of the area has degenerated. Only the coarse rugulate fringes along area margins are still present and mark the fines.
Holotype: Below, 1987, pl. 2, fig. 1-2, 4
Stratum typicum: Toarcian
Locus typicus: Knerten Hill near DeGeerdalen, Spitsbergen
Translation Below, 1987: Secretary of State, Canada, Translation Bureau
Original description: Below, 1987, p. 14-16.
Diagnosis (annotated): Arrangement of vesicles/plates on the dinoflagellate amphiesma PR, 5", 3a, 7"", 7c, 6""", 2"""", as, FM subdivided into several periflagellar platelets, ls, rs, ps; pentogonal 1"""" and hexagonal 2"""" partiform; omegaform ps very large. Cyst habit proximate, acavate, ovaloidal to polyhedral, epicyst transversely semi-ellipsoidal, apically rounded, somewhat smaller than the semi-ovoidal hypocyst with rounded antapex; size small; wall composed of pedium and spongy luxuria, surface rugulate, areate, the surface of the area homologous to an overlapping plate raised above the area homologous to the overlapped plate sloping down towards it at a sharp gradient along the finis, overlapping margins sometimes edged by coarse rugulae; areation formula NR PR/XPR, NR"/5", 3a, 7"", 7c, 6""", 2"""", as, FM, ls, rs, ps; PR undifferentiated or not reflected; 5 very small apicals, VI 1" (V) with porichnion on finis 1"/5", deltaform inverse-camerate 2" (VL), IV- nE 3" (L), IV-nE 4" (R), deltaform inverse-camerate 5" (VR); 3 small anterior intercalaries, deltaform inverse-camerate 1a (DL), deltaform linteloid or VII 2a (D), deltaform inverse-camerate 3a (R); 7 precingulars, anteriorly geniculate V-nE 1"" (VVL), anteriorly geniculate V-nE 2"" (L), anteriorly geniculate V-nE 3"" (DL), anteriorly linear IV-nE 4"" (D), anteriorly geniculate V-nE 5"" (DR), anteriorly geniculate V-nE 6"" (RVR), small anteriorly geniculate V-nE 7"" (VVR); cingulum helicoid laevorotatory, indented, heptaareate with lati 1c to 6c and fastigiate 7c; 6 postcingulars, posteriorly linear V-nE 1""" (VVL), posteriorly linear IV-nE 2""" (VL), posteriorly geniculate V-nE 3""" (DL), posteriorly linear IV-nE 4""" (D), posteriorly linear IV-nE 5""" (RDR), posteriorly linear V-nE 6 """ (VR); 2 antapicals partiform, V 1"""" descending towards LVL, VI 2"""" towards R; hypocystal sulcus indented, comprising V as, FM, small caroidal rs and ls, and large, omegaform VI ps; archeopyle apical, amplificate, 2" + 3"; operculum solvate, secate, general opercular formula 2"s + 3"s.
Dimensions of holotype: Length, 30 Ám, breadth, 27 Ám, thickness 27 Ám.
Remarks: This species is extraordinarily interesting because of the reflection of thecal-plate growth structures. On most specimens, the overlapping system is directly readable almost in full, and it is shown on the areation diagram (Figure 3). As can be demonstrated also for taxa of the tribe Phanerodinieae, usually 4""" is the culmen of the primtegulate hypocystal overlap series, but specimens with 3""" as culmen were also observed (Plate 2, fig. 11, 13). The ridge-tile areae are very prominent. At the fines bordering the areae reflecting the overlapped plates, they descend abruptly to the normal level of the cyst surface. The area reflecting the overlapped plate is often structured like a ramp. From the margin where its homologous plate was overlapped, its surface rises uniformly to the margin where the corresponding plate, in turn, overlapped its neighbor. There it stands out like the ridge-tile area. This arrangement, which is reminiscent of a paddle wheel, is seen most clearly in a polar aspect of the cyst (Plate 2, Fig. 11, 12 and 15). In addition, the overlapping margins frequently are edged by coarse rugulae. Perhaps these rugulate fringes on the areae reflect zones of increment on thecal plates. In that case, growth and overlapping would be correlated as in the Gonyaulax type of thecal-plate growth. If we use the character of overlapping areae descending like steps towards the overlapped areae to reconstruct the overlapping at the cingulum as well, then the transverse furrow on the theca was overlapped by precingular and by postcingular plates. The level of overlap is lower on the precingular side than on the postcingular. An important, albeit seldom illustrated detail of the areation is the porichnion on finis 1"/5". It may permit us to homologize area 5" of Mikrocysta with 4" of taxa of the tribe Phanerodinieae (see p. 13). As a rule, the surface between 1", the anterior intercalaries, 2", and 5" is undivided, as in Mikrocysta erugata, so that there appear to be only four apical areae in all. However, specimen S2- 805(KO-1)1/1 (Plate 2, Fig. 15) shows schematic relicts of two low circles of ribs in a peniareate position, which represent 3" and 4". In contrast to Mikrocysta erugata, only three anterior intercualries are discernible. The additional, minute trigonal area (2a anterior to 3"" in Mikrocysta erugata) was either not originally present on the theca, or not reflected, or reflected inadequately. Possibly the surfaces of the corresponding thecal plates were too small to be reflected as areae, so that they were reflected only by ornaments (thus, e.g., cop is often reflected by a granule, verruca, or baculum), which however, are no longer visible among the coarsely rugulate surface ornamentation of this species. The configuration of areae is: PR (1", 2", 3", 4", 5"), 1" (as, 1"", 2", PR, 5", 7""), 2" (PR, 1", 1"", 2"", 1a, 3"), 3" (PR, 2", 1a, 2a, 4a), 4" (PR, 3", 2a, 3a, 5"), 5" ( PR, 4", 3a, 6"", 7"", 1"), 1a (2"", 3"", 2a, 3", 2"), 2a (3"", 4"", 5"", 3a, 4", 3", 1a), 3a (5"", 6"", 5", 4", 2a), 1"" (c, 2"", 2", 1", as), 2"" (c, 3"", 1a, 2", 1""), 3"" (c, 4"", 2a, 1a, 2""), 4"" (c, 5"", 2a, 3""), 5"" (c, 6"", 3a, 2a, 4""), 6"" (c, 7"", 5", 3a, 5""), 7"" (c, as, 1", 5", 6""), as (1", 7"", c, FM, c, 1""), 1""" (c, s, 1"""", 2"""), 2""" (c, 1""", 1"""", 3"""), 3""" (c, 2""", 1"""", 2"""", 4"""), 4""" (c, 3""", 2"""", 5"""), 5""" (c, 4""", 2"""", 6"""), 6""" (c, 5""", 2"""", s), 1"""" (1""", 2""", 3""", 2"""", s), 2"""" (1"""", 3""", 4""", 5""", 6""", s).
The surface bears rugulae usually very tightly coiled liked intestines. They may be bevelled (Plate 2, Fig. 7, 8, 9, 11, 12, and 14) or reduced to granules (Plate 3, Fig. 4) or completely absent on intraareate surfaces. Figures 1-6 on Plate 3 show another variant of this species. The ramp-like structure of the area has degenerated. Only the coarse rugulate fringes along area margins are still present and mark the fines.