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Palaecysta
From Williams et al., 2017:
[Palaecysta, Chen, 2013, p. 288–289.
Type species: Palaecysta integra, Chen, 2013 (pl.1, fig.1)]
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Original description [Chen et al., 2013]:
Synopsis:
Cysts skolochorate, gonyaulacacean, sexiform; central body subspherical, normally slightly dorso-ventrally compressed, with 18 membranous process clusters and up to 18 singular spinous processes, neither of which are distally linked (Figure 4). The membranous process clusters arcuate in the apical, precingular, and postcingular series, whereas annulate in the antapical series. The singular spinous processes are restricted to the parasulcus and paracingular series, and sometimes show up in the first postcingular paraplate. Archeopyle apical, Type tA (sensu Stover & Evitt, 1978) (Figure 4; Figure 5C; Figures 8B, 8C, 8D). The criteria for the differentiation at species and subspecies levels are largely based on the expressions of the process clusters.
Descriptions:
Shape: Body subspherical.
Wall relationships: Endophragm and periphragm appressed, or autophragm only.
Wall features: Parasutural features generally present, expressed by accessory archeopyle sutures, of up to one-third of a paraplate length, in areas between the precingular paraplates (Figures 4-8). Processes and process clusters intratabular.
Processes: Single spinous processes and membranous process clusters, neither of which are distally linked. Process clusters (total 18), arcuate in the apical, precingular, and postcingular, annulate in the antapical paraplate, flare distally, with or without branching, and with or without foveolation or reticulation. Single processes (up to 18), straight or bent, long, and tapered; restricted to paracingular and parasulcal paraplates. The arcuate process clusters in the apical series open towards the dorsoventral axis, and in the precingular and postcingular series, open towards the paracingulum (Figure 4). Pre-apical paraplates may be present, indicated by low-relief three to four granulate protrusions (Figure 5C). The first postcingular expression can be either process or process cluster; but when only five postcingular process clusters present, they are interpreted to be from paraplates 2000 to 6000 (Figure 4). The posterior intercalary paraplate can be expressed as annulate (Figures 6, 7), or arcuate (Figure 5) process cluster, its size similar to most of those postcingular series. The anterior sulcal process often well-established (Figures 5-7).
Paratabulation: Indicated by the process clusters, processes, and granulate protrusions; gonyaulacacean, process formula: 0-3 pr, 4’, 6’’, 6c, 6’’’, 1p, 1’’’’, 0-7s.
Archeopyle: Apical, Type tA; principal archeopyle suture slightly zigzag and parasulcal notch sometimes conspicuous; operculum free (Figure 4; Figure 5C).
Paracingulum: Indicated by 6 pairs of spinous processes, unlinked at the base.
Parasulcus: Indicated frequently by 5 to 7 single spinous processes.
Size: Mostly large (100 to 150 µm) with few intermediate (80 to 100 µm).
Affinities/Comparison:
Palaecysta differs from Systematophora Klement 1960 in having arcuate membranous, not annulate process clusters, in the pre- and postcingular series. The two genera further differ in that the former lacks while the latter genus possesses ridge-like structures linking the pair of spinous processes for each of its paracingular paraplates (Plate 14, Figures 160). “Amphorula” (now Amphorulacysta, see Systematic palynology), similar to Systematophora, also possesses linkage for their paracingular process pairs (Plate 14, Figures 159), with which it differs from Palaecysta. The two genera further differ in Amphorulacysta being proximochorate while Palaecysta comprising skolochorate cysts. More comparison with other morphologically similar genera can be found in Section 5.1. Discussion All the species in this genus possess exclusively arcuate process clusters and no intraspecies variation of different process cluster type (such as annulate ones) exists in any specimens from any of the Madagascar species. The arcuate process cluster has been observed to be a stable and consistent characteristic throughout the studied interval from the Ankamatra-1 well, which is the justification to erect this group into a distinct genus.
[Palaecysta, Chen, 2013, p. 288–289.
Type species: Palaecysta integra, Chen, 2013 (pl.1, fig.1)]
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description [Chen et al., 2013]:
Synopsis:
Cysts skolochorate, gonyaulacacean, sexiform; central body subspherical, normally slightly dorso-ventrally compressed, with 18 membranous process clusters and up to 18 singular spinous processes, neither of which are distally linked (Figure 4). The membranous process clusters arcuate in the apical, precingular, and postcingular series, whereas annulate in the antapical series. The singular spinous processes are restricted to the parasulcus and paracingular series, and sometimes show up in the first postcingular paraplate. Archeopyle apical, Type tA (sensu Stover & Evitt, 1978) (Figure 4; Figure 5C; Figures 8B, 8C, 8D). The criteria for the differentiation at species and subspecies levels are largely based on the expressions of the process clusters.
Descriptions:
Shape: Body subspherical.
Wall relationships: Endophragm and periphragm appressed, or autophragm only.
Wall features: Parasutural features generally present, expressed by accessory archeopyle sutures, of up to one-third of a paraplate length, in areas between the precingular paraplates (Figures 4-8). Processes and process clusters intratabular.
Processes: Single spinous processes and membranous process clusters, neither of which are distally linked. Process clusters (total 18), arcuate in the apical, precingular, and postcingular, annulate in the antapical paraplate, flare distally, with or without branching, and with or without foveolation or reticulation. Single processes (up to 18), straight or bent, long, and tapered; restricted to paracingular and parasulcal paraplates. The arcuate process clusters in the apical series open towards the dorsoventral axis, and in the precingular and postcingular series, open towards the paracingulum (Figure 4). Pre-apical paraplates may be present, indicated by low-relief three to four granulate protrusions (Figure 5C). The first postcingular expression can be either process or process cluster; but when only five postcingular process clusters present, they are interpreted to be from paraplates 2000 to 6000 (Figure 4). The posterior intercalary paraplate can be expressed as annulate (Figures 6, 7), or arcuate (Figure 5) process cluster, its size similar to most of those postcingular series. The anterior sulcal process often well-established (Figures 5-7).
Paratabulation: Indicated by the process clusters, processes, and granulate protrusions; gonyaulacacean, process formula: 0-3 pr, 4’, 6’’, 6c, 6’’’, 1p, 1’’’’, 0-7s.
Archeopyle: Apical, Type tA; principal archeopyle suture slightly zigzag and parasulcal notch sometimes conspicuous; operculum free (Figure 4; Figure 5C).
Paracingulum: Indicated by 6 pairs of spinous processes, unlinked at the base.
Parasulcus: Indicated frequently by 5 to 7 single spinous processes.
Size: Mostly large (100 to 150 µm) with few intermediate (80 to 100 µm).
Affinities/Comparison:
Palaecysta differs from Systematophora Klement 1960 in having arcuate membranous, not annulate process clusters, in the pre- and postcingular series. The two genera further differ in that the former lacks while the latter genus possesses ridge-like structures linking the pair of spinous processes for each of its paracingular paraplates (Plate 14, Figures 160). “Amphorula” (now Amphorulacysta, see Systematic palynology), similar to Systematophora, also possesses linkage for their paracingular process pairs (Plate 14, Figures 159), with which it differs from Palaecysta. The two genera further differ in Amphorulacysta being proximochorate while Palaecysta comprising skolochorate cysts. More comparison with other morphologically similar genera can be found in Section 5.1. Discussion All the species in this genus possess exclusively arcuate process clusters and no intraspecies variation of different process cluster type (such as annulate ones) exists in any specimens from any of the Madagascar species. The arcuate process cluster has been observed to be a stable and consistent characteristic throughout the studied interval from the Ankamatra-1 well, which is the justification to erect this group into a distinct genus.