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Hystrichokolpoma tumescens
From Fensome et al., 2019:
Hystrichokolpoma tumescens McLean, 1974, p.66,68, pl.8, figs.6–9; text-fig.1A. Holotype: McLean, 1974, pl.8, figs.7–8. Age: Late Paleocene.
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Locus typicus: Potomac River, S of Washington, U.S.A.
Stratum typicum: Late Paleocene
Original diagnosis: McLean, 1974, p.66
A species of Hystrichokolpoma with a large, bulbous antapical process.
Original description: McLean, 1974, p.68
Cyst main body ellipsoidal, bearing simulate, hollow, bix-like processes. Cyst wall bi-layered; processes, formed of the periphragm, reflect tabulation of 4?', 0a, 6", 6c, 6''', 1p, 1''''. Archeopyle apical (Type A) with simple, free operculum; corresponds to 4(?) apical plates. Cingulum and sulcus reflected by processes. Cingulum levorotatory, ends separated vertically up to one cingulum width and transversely up to one and one-half cingulum widths. Sulcal area reflected at top and bottom by anterior and posterior sulcal processes, respectively, ancl in between by two pairs of small processes. Of the anterior-most pair the left member is the larger and is designated as the 1'''; the other pair is between processes 6''' and 1p. Individual processes of the two small process pairs occur either as single spine-like elements, or as several spine-like elements branching from a common base.
Wall layers appressed except under processes. Endophragm c. 0.75 - 1.25 µm thick, and smooth to faintly granulose externally. Periphragm c. 0.5 µm thick, and smooth to faintly granulose externally. Processes simulate, one per plate-equivalent, hollow and box-like, closed ancl denticulate at tips, non branching except for 1p and sulcal processes, externally smooth, faintly striate, or faintly granulose, and may show numerous tiny longitudinal folds; do not communicate with endocoel. Precingular processes nearly equidimensional except for relatively small 6" process. Processes 2", 4", and 6" have four-sided bases, and processes 1", 3", and 5" have five-sided bases. Cingular process bases rectangular. Postcingular process bases characteristically four-sided; processes 3''', 4''', and 5''' are largest. 6''' is intermediate in size, and 1''' is smallest. Process 1p has an irregular basal outline, and may branch into several spine-like elements. Antapical process bulbous, with pentagonal base and narrow, drawn-out tip which may be broken open.
Dimensions: Holotype main body L x W (excluding operculum which is missing): 45x37 µm; processes up to 25 µm long; antapical process 37 µm long by 26-31 µm at base. Observed range- main body length (excluding opercula which were universally missing) 45-62 µm (mean 52 µm); main body transdiameter: 37-53 µm (mean 42 µm), length of main body together with antapical process 76-99 µm.
Hystrichokolpoma tumescens McLean, 1974, p.66,68, pl.8, figs.6–9; text-fig.1A. Holotype: McLean, 1974, pl.8, figs.7–8. Age: Late Paleocene.
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Locus typicus: Potomac River, S of Washington, U.S.A.
Stratum typicum: Late Paleocene
Original diagnosis: McLean, 1974, p.66
A species of Hystrichokolpoma with a large, bulbous antapical process.
Original description: McLean, 1974, p.68
Cyst main body ellipsoidal, bearing simulate, hollow, bix-like processes. Cyst wall bi-layered; processes, formed of the periphragm, reflect tabulation of 4?', 0a, 6", 6c, 6''', 1p, 1''''. Archeopyle apical (Type A) with simple, free operculum; corresponds to 4(?) apical plates. Cingulum and sulcus reflected by processes. Cingulum levorotatory, ends separated vertically up to one cingulum width and transversely up to one and one-half cingulum widths. Sulcal area reflected at top and bottom by anterior and posterior sulcal processes, respectively, ancl in between by two pairs of small processes. Of the anterior-most pair the left member is the larger and is designated as the 1'''; the other pair is between processes 6''' and 1p. Individual processes of the two small process pairs occur either as single spine-like elements, or as several spine-like elements branching from a common base.
Wall layers appressed except under processes. Endophragm c. 0.75 - 1.25 µm thick, and smooth to faintly granulose externally. Periphragm c. 0.5 µm thick, and smooth to faintly granulose externally. Processes simulate, one per plate-equivalent, hollow and box-like, closed ancl denticulate at tips, non branching except for 1p and sulcal processes, externally smooth, faintly striate, or faintly granulose, and may show numerous tiny longitudinal folds; do not communicate with endocoel. Precingular processes nearly equidimensional except for relatively small 6" process. Processes 2", 4", and 6" have four-sided bases, and processes 1", 3", and 5" have five-sided bases. Cingular process bases rectangular. Postcingular process bases characteristically four-sided; processes 3''', 4''', and 5''' are largest. 6''' is intermediate in size, and 1''' is smallest. Process 1p has an irregular basal outline, and may branch into several spine-like elements. Antapical process bulbous, with pentagonal base and narrow, drawn-out tip which may be broken open.
Dimensions: Holotype main body L x W (excluding operculum which is missing): 45x37 µm; processes up to 25 µm long; antapical process 37 µm long by 26-31 µm at base. Observed range- main body length (excluding opercula which were universally missing) 45-62 µm (mean 52 µm); main body transdiameter: 37-53 µm (mean 42 µm), length of main body together with antapical process 76-99 µm.