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Aprobolocysta bipartita
Aprobolacysta bipartita, Backhouse, 1987
Originally (and now) Aprobolocysta, subsequently Necrobroomea. Below, 1990, transferred this species to Necrobroomea Wiggins, 1975. Lentin and Williams, 1993, retained this species in Aprobolocysta.
Holotype: Backhouse 1987, figs.9E-F
Locus typicus: Perth basin, Australia
Stratum typicum: Middle Hauterivian
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Original description: [Backhouse, 1987, p. 212]:
Description:
Cyst small, proximate, elongate and ovoidal.
Apex rounded without an apical horn; 2 short antapical horns developed by the endophragm; left horn slightly longer than the right.
Endophragm finely granular, approximately 0.5 µm thick; periphragm thinner, appressed to the endophragm in the apical, cingular, anterior sulcal, and antapical areas, slightly raised and tightly folded or wrinkled elsewhere.
Archeopyle apical, probably type [tA]; operculum usually missing. Principal archeopyle suture with a deep sulcal notch and a short gabled paraplate to the left of the sulcal notch.
Accessory sutures and the morphology of the periphragm not delineating a precise paratabulation.
Dimensions:
Total length of holotype 62 µm, width across the hypocyst 34 µm.
Range of length with operculum missing (11 specimens) 39(51)61 µm, width 31(35)43 µm.
Affinities:
Aprobolocysta bipartita is similar in overall shape and structure to A. galeata. It is distinguished from A. galeata by possessing longer antapical horns and a tightly folded periphragm only in the precingular and postcingular areas. The absence of high, rounded, periphragmal folds distinguishes A. bipartita from A . alata. From the stratigraphic distribution of A. galeata, A. bipartita and A. alata it is concluded that these species form a morphocline. The transition from A. bipartita to A. alata takes place at, or just below the base of the A. alata Zone.
Originally (and now) Aprobolocysta, subsequently Necrobroomea. Below, 1990, transferred this species to Necrobroomea Wiggins, 1975. Lentin and Williams, 1993, retained this species in Aprobolocysta.
Holotype: Backhouse 1987, figs.9E-F
Locus typicus: Perth basin, Australia
Stratum typicum: Middle Hauterivian
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Backhouse, 1987, p. 212]:
Description:
Cyst small, proximate, elongate and ovoidal.
Apex rounded without an apical horn; 2 short antapical horns developed by the endophragm; left horn slightly longer than the right.
Endophragm finely granular, approximately 0.5 µm thick; periphragm thinner, appressed to the endophragm in the apical, cingular, anterior sulcal, and antapical areas, slightly raised and tightly folded or wrinkled elsewhere.
Archeopyle apical, probably type [tA]; operculum usually missing. Principal archeopyle suture with a deep sulcal notch and a short gabled paraplate to the left of the sulcal notch.
Accessory sutures and the morphology of the periphragm not delineating a precise paratabulation.
Dimensions:
Total length of holotype 62 µm, width across the hypocyst 34 µm.
Range of length with operculum missing (11 specimens) 39(51)61 µm, width 31(35)43 µm.
Affinities:
Aprobolocysta bipartita is similar in overall shape and structure to A. galeata. It is distinguished from A. galeata by possessing longer antapical horns and a tightly folded periphragm only in the precingular and postcingular areas. The absence of high, rounded, periphragmal folds distinguishes A. bipartita from A . alata. From the stratigraphic distribution of A. galeata, A. bipartita and A. alata it is concluded that these species form a morphocline. The transition from A. bipartita to A. alata takes place at, or just below the base of the A. alata Zone.