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Licracysta corymbus
Licracysta corymbus Fensome et al., 2007, p.402,404,406,408, pl.4, figs.5–6,9–20, pl.5, figs.1–8,12,16,20.
Holotype: Fensome et al., 2007, pl.4, figs.9–12.
Age: youngest occurrence, Rupelian.
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Original description (Fensome et al., 2007):
Licracysta corymbus Fensome, Guerstein and Williams, n. sp. Plate 4, figures 5-6, 9-20; plate 5, figures 1-8, 12, 16, 20
Derivation of name: From the Latin corymbus (Greek “korymbos”) for “bunch of flowers”, in reference to the clustered, contabular nature of many of the processes in this species. The epithet is a noun in apposition and its ending should not be changed to agree with the gender of the genus.
Diagnosis: A species of Licracysta with numerous and variable processes, mostly marginately distributed and in contabular complexes, although relatively simple mesotabular processes may occasionally be present. Processes in each contabular complex may be isolated, connected in part by proximal ridges, or connected variably along their length by trabecula or membranes. Each specimen always has at least two contabular complexes with interconnections above the base.
Description Shape: Cyst proximochorate to chorate with a lenticular central body, dorsoventrally compressed and with a slightly offset sulcal notch. Antapex commonly asymmetrical, more pronounced on the left side. Wall relationships: Autophragm only. Wall features: Autophragm scabrate to granular, the granules especially in dorsoventral areas sometimes developed into short irregular rugulae and even an irregular microreticulum. Central body with numerous and variable processes, mostly marginately distributed. Relatively simple mesotabular processes may occasionally be present, but processes are most commonly distributed in contabular complexes. Processes in each complex may be isolated, connected in part by proximal ridges, or connected variably along their length by trabecula or membranes. Each specimen always has at least two contabular complexes with interconnections above the base. The distal terminations of the processes may be acuminate, irregularly branched or, most typically, dolabrate to weakly licrate. Archeopyle: Apical, type (tA); operculum tetratabular, simple and free. Tabulation: Expressed anteriorly by archeopyle sutures. Otherwise, isolated processes (especially marking plates 3'' and 6'') and contabular groups of processes (postcingulars and lateral precingulars) give a general sense of the tabulation. The cingulum can sometimes be distingushed by an equatorial thinning out of processes. The antapical plate is sometimes suggested by a distinctive duo of “inturned” processes and rarely its dorsal anterior boundary appears to be marked by a low ridge that seems to be penitabular. The sulcus is indicated by the offset sulcal notch.
Dimensions: Range of 10 specimens: central body width 59 (64) 73µm; length (excluding operculum) 50 (54) 64µm; process length up to 17 (22) 26µm; maximum process length as a percentage of central body width 23 (34) 42 percent.
Holotype: Plate 4, figures 9-12.
Location: sample P25 [sample depth 978.4-987.9m (3210-3241 feet; cuttings sample)]; slide 10, co-ordinates 16.0 x 94.5, England Finder P37/4.
Repository: GSC type collection no. 128918.
Dimensions: central body width 62µm, central body length 51µm, processes up to 26µm long.
Geographic occurrence: Onondaga E-84 well (Geological Survey of Canada, Atlantic locality no. D2), Scotian Margin, offshore eastern Canada.
Age: The sample is dated as Early Oligocene (Fensome 2001). Although the holotype is from a cuttings sample and possibly caved, the range top for this species is within the Early Oligocene (RAF, unpublished observations).
Occurrence: The range top of this species is Rupelian (early Oligocene) based on dinocyst assemblages. The base of its range has not been established.
Comparison: Licracysta corymbus differs from species of Cleistosphaeridium in having dorsoventral area that are completely devoid or processes or almost so. Forms in the Cleistosphaeridium diversispinosum/ancyreum complex have processes that are more uniform in morphology and generally simpler distally.
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Holotype: Fensome et al., 2007, pl.4, figs.9–12.
Age: youngest occurrence, Rupelian.
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Original description (Fensome et al., 2007):
Licracysta corymbus Fensome, Guerstein and Williams, n. sp. Plate 4, figures 5-6, 9-20; plate 5, figures 1-8, 12, 16, 20
Derivation of name: From the Latin corymbus (Greek “korymbos”) for “bunch of flowers”, in reference to the clustered, contabular nature of many of the processes in this species. The epithet is a noun in apposition and its ending should not be changed to agree with the gender of the genus.
Diagnosis: A species of Licracysta with numerous and variable processes, mostly marginately distributed and in contabular complexes, although relatively simple mesotabular processes may occasionally be present. Processes in each contabular complex may be isolated, connected in part by proximal ridges, or connected variably along their length by trabecula or membranes. Each specimen always has at least two contabular complexes with interconnections above the base.
Description Shape: Cyst proximochorate to chorate with a lenticular central body, dorsoventrally compressed and with a slightly offset sulcal notch. Antapex commonly asymmetrical, more pronounced on the left side. Wall relationships: Autophragm only. Wall features: Autophragm scabrate to granular, the granules especially in dorsoventral areas sometimes developed into short irregular rugulae and even an irregular microreticulum. Central body with numerous and variable processes, mostly marginately distributed. Relatively simple mesotabular processes may occasionally be present, but processes are most commonly distributed in contabular complexes. Processes in each complex may be isolated, connected in part by proximal ridges, or connected variably along their length by trabecula or membranes. Each specimen always has at least two contabular complexes with interconnections above the base. The distal terminations of the processes may be acuminate, irregularly branched or, most typically, dolabrate to weakly licrate. Archeopyle: Apical, type (tA); operculum tetratabular, simple and free. Tabulation: Expressed anteriorly by archeopyle sutures. Otherwise, isolated processes (especially marking plates 3'' and 6'') and contabular groups of processes (postcingulars and lateral precingulars) give a general sense of the tabulation. The cingulum can sometimes be distingushed by an equatorial thinning out of processes. The antapical plate is sometimes suggested by a distinctive duo of “inturned” processes and rarely its dorsal anterior boundary appears to be marked by a low ridge that seems to be penitabular. The sulcus is indicated by the offset sulcal notch.
Dimensions: Range of 10 specimens: central body width 59 (64) 73µm; length (excluding operculum) 50 (54) 64µm; process length up to 17 (22) 26µm; maximum process length as a percentage of central body width 23 (34) 42 percent.
Holotype: Plate 4, figures 9-12.
Location: sample P25 [sample depth 978.4-987.9m (3210-3241 feet; cuttings sample)]; slide 10, co-ordinates 16.0 x 94.5, England Finder P37/4.
Repository: GSC type collection no. 128918.
Dimensions: central body width 62µm, central body length 51µm, processes up to 26µm long.
Geographic occurrence: Onondaga E-84 well (Geological Survey of Canada, Atlantic locality no. D2), Scotian Margin, offshore eastern Canada.
Age: The sample is dated as Early Oligocene (Fensome 2001). Although the holotype is from a cuttings sample and possibly caved, the range top for this species is within the Early Oligocene (RAF, unpublished observations).
Occurrence: The range top of this species is Rupelian (early Oligocene) based on dinocyst assemblages. The base of its range has not been established.
Comparison: Licracysta corymbus differs from species of Cleistosphaeridium in having dorsoventral area that are completely devoid or processes or almost so. Forms in the Cleistosphaeridium diversispinosum/ancyreum complex have processes that are more uniform in morphology and generally simpler distally.
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