Back
Gordiacysta
From Fensome et al., 2019:
Gordiacysta, Miles, 1990, p.84,86,88.
Type: Miles, 1990, pl.3, figs.1–2, as Gordiacysta coronata.
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Miles, 1990]:
Diagnosis:
Chorate dinoflagellate cysts with speroidal main body (autophragm only) and an apical and antapical horn.
Three groups of processes are arranged around apical, precingular/postcingular and antapical regions. Four processes are present in the apical region; each process is linked by trabeculae to the adjacent processes, forming a crown-like structure around the apical horn. Six precingular and six postcingular processes are interconnected to form a trabeculate network. In cross-section, the processes are mainly arcuate in shape. Of the six precingular processes, four are more prominent, strongly recurved, and distally bifurcate in the direction of the antapex. The remaining two are smaller and bifurcate. Four of the six postcingular processes are also more prominent, and two are somewhat smaller. The larger processes are strongly recurved and trifurcate, while the smaller processes are bifurcate. The trabeculate network that joins these processes consists of direct connections between adjacent postcingular processes, and connections between postcingular and precingular processes mainly at triple junctions over the cingular area. Adjacent precingular processes are interconnected only at these triple junctions. Another less prominent interconnection between the precingular and postcingular areas is associated with the two smaller processes in each series. Other, usually very tenuous, projections may arise from the autophragm and join the trabeculate network. The development of these smaller processes is highly variable. Faint trabecular strands may be developed between the proximal parts of the apical and precingular processes. A conical antapical horn is formed by the merging of the antapical process group.
A free, single-plate, precingular archeopyle is developed. This and the general process distribution are characteristic of a gonyaulacoid formula.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Gonyaulacysta Deflandre, 1964, emend. Helenes and Lucas-Clark, 1997. According to Helenes and Lucas-Clark (1997), Gonyaulacysta is characterized by well-developed apical horn and cavation, elliptical cingular cross-section, and a paratabulation pattern including the contacts 1u/1i (1`/6"), A/li(4`/6"), ai/II(as/2"' ), and the presence of accessory K intercalary paraplates. Forms included are known only from the Jurassic. The genus now includes G. jurassica, G.dualis and G.pectinigera. The genus may be bicavate, cornucavate or suturocavate. It has a symmetrical rectangular Y(1"" ). The archeopyle is P(3"), resulting from the loss of the third precingular.
Gordiacysta, Miles, 1990, p.84,86,88.
Type: Miles, 1990, pl.3, figs.1–2, as Gordiacysta coronata.
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Miles, 1990]:
Diagnosis:
Chorate dinoflagellate cysts with speroidal main body (autophragm only) and an apical and antapical horn.
Three groups of processes are arranged around apical, precingular/postcingular and antapical regions. Four processes are present in the apical region; each process is linked by trabeculae to the adjacent processes, forming a crown-like structure around the apical horn. Six precingular and six postcingular processes are interconnected to form a trabeculate network. In cross-section, the processes are mainly arcuate in shape. Of the six precingular processes, four are more prominent, strongly recurved, and distally bifurcate in the direction of the antapex. The remaining two are smaller and bifurcate. Four of the six postcingular processes are also more prominent, and two are somewhat smaller. The larger processes are strongly recurved and trifurcate, while the smaller processes are bifurcate. The trabeculate network that joins these processes consists of direct connections between adjacent postcingular processes, and connections between postcingular and precingular processes mainly at triple junctions over the cingular area. Adjacent precingular processes are interconnected only at these triple junctions. Another less prominent interconnection between the precingular and postcingular areas is associated with the two smaller processes in each series. Other, usually very tenuous, projections may arise from the autophragm and join the trabeculate network. The development of these smaller processes is highly variable. Faint trabecular strands may be developed between the proximal parts of the apical and precingular processes. A conical antapical horn is formed by the merging of the antapical process group.
A free, single-plate, precingular archeopyle is developed. This and the general process distribution are characteristic of a gonyaulacoid formula.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Gonyaulacysta Deflandre, 1964, emend. Helenes and Lucas-Clark, 1997. According to Helenes and Lucas-Clark (1997), Gonyaulacysta is characterized by well-developed apical horn and cavation, elliptical cingular cross-section, and a paratabulation pattern including the contacts 1u/1i (1`/6"), A/li(4`/6"), ai/II(as/2"' ), and the presence of accessory K intercalary paraplates. Forms included are known only from the Jurassic. The genus now includes G. jurassica, G.dualis and G.pectinigera. The genus may be bicavate, cornucavate or suturocavate. It has a symmetrical rectangular Y(1"" ). The archeopyle is P(3"), resulting from the loss of the third precingular.