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Alisocysta brevivallata
Alisocysta brevivallata, Harker and Sarjeant in Harker et al., 1990 ex Harker and Sarjeant, 1991
This name was not validly published in Harker et al. (1990), since the lodgement of the holotype was not cited (I.C.N. Article 40.7).
Holotype: Harker et al., 1990, pl.5, figs.11,12
Locus typicus: La Riviere, Manitoba, Canada
Stratum typicum: Campanian
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Original description: [Harker, Sarjeant and Caldwell, 1990, p. 97]
Diagnosis:
Small proximate cysts having a spheroidal to ovoidal ambitus.
Phragma thin, composed of two closely adpressed layers; endophragm smooth to finely granular, periphragm giving rise to short capitate spines that support low connecting crests forming simulate complexes.
These penitabular crests outline the paratabulation 4", (?)6", 6c, 1-5s(?), 6""", 1p, 1"""". The complexes are separated by fossae that are generally bare of ornamentation other than rare isolate, coarse granules but are in places traversed by low ridges. Poorly developed accessory crests give rise to a partial reticulation on some paraplates. Cingulum slightly laevorotatory; sulcus of moderate breadth.
Archaeopyle apical, with deep parasutural notches and a free operculum.
Description:
The low penitabular crests are supported by short capitate spines (Pl. 5, Fig. 17), a structure very similar to that observed in Cassieulosphaeridia magna and C. ovalis (Pl. 2, Fig. 10 and Pl. 2, Fig. 12). Since the penitabular crests are often poorly developed in the apical and ventral regions and since the apex is missing in most specimens, the full paratabulation is difficult to determine; however, it appears to be that typical for the genus. The cingular paraplate series is easily recognized and is slightly laevorotatory, sulcal displacement being by about one cingulum width. A partial reticulation is produced by poorly developed, discontinuous spine-supported crests; this feature is not equally developed on every specimen (compare Pl. 5, Fig. 12 and Pl. 5, Fig. 14). The fossae separating the paraplates are generally smooth with only a few, scattered granules (relief less than 0.5 µm). However, they are in places traversed by low ridges related in position to accessory crests on adjacent peniplates; these surely correspond to lines demarcating growth phases of the motile dinoflagellate.
The archaeopyle is formed by loss of all the apical paraplates; its angular margin has deep parasutural notches (Pl. 5, Fig. 16).
Dimensions:
Holotype: length (apex missing) 26 µm, breadth 29 µm, height of crests 0.5-1.5 µm, width 0.5-1.0 µm.
Range of 61 measurable specimens: length (apex missing) 25-37 µm, mean 31 µm; breadth 25-37 µm, mean 29 µm; height of crests 0.5-2.0 µm; width 0.5-1.0 µm.
Affinities: (p. 98):
The low, spine-supported crests distinguish this from all other species of Alisocysta. A. ornata (Cookson and Eisenack, 1965) Stover and Evitt 1978 and A. circumtabulata (Drugg 1967) Stover and Evitt 1978 are similar, but differ respectively in having smooth, distally tapering penitabular ridges or high, membranous penitabular crests. The specimens illustrated by Leopold & Tschudy (1965, Figs. 237, 238) appear similar in size and morphology to those observed.
This name was not validly published in Harker et al. (1990), since the lodgement of the holotype was not cited (I.C.N. Article 40.7).
Holotype: Harker et al., 1990, pl.5, figs.11,12
Locus typicus: La Riviere, Manitoba, Canada
Stratum typicum: Campanian
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Harker, Sarjeant and Caldwell, 1990, p. 97]
Diagnosis:
Small proximate cysts having a spheroidal to ovoidal ambitus.
Phragma thin, composed of two closely adpressed layers; endophragm smooth to finely granular, periphragm giving rise to short capitate spines that support low connecting crests forming simulate complexes.
These penitabular crests outline the paratabulation 4", (?)6", 6c, 1-5s(?), 6""", 1p, 1"""". The complexes are separated by fossae that are generally bare of ornamentation other than rare isolate, coarse granules but are in places traversed by low ridges. Poorly developed accessory crests give rise to a partial reticulation on some paraplates. Cingulum slightly laevorotatory; sulcus of moderate breadth.
Archaeopyle apical, with deep parasutural notches and a free operculum.
Description:
The low penitabular crests are supported by short capitate spines (Pl. 5, Fig. 17), a structure very similar to that observed in Cassieulosphaeridia magna and C. ovalis (Pl. 2, Fig. 10 and Pl. 2, Fig. 12). Since the penitabular crests are often poorly developed in the apical and ventral regions and since the apex is missing in most specimens, the full paratabulation is difficult to determine; however, it appears to be that typical for the genus. The cingular paraplate series is easily recognized and is slightly laevorotatory, sulcal displacement being by about one cingulum width. A partial reticulation is produced by poorly developed, discontinuous spine-supported crests; this feature is not equally developed on every specimen (compare Pl. 5, Fig. 12 and Pl. 5, Fig. 14). The fossae separating the paraplates are generally smooth with only a few, scattered granules (relief less than 0.5 µm). However, they are in places traversed by low ridges related in position to accessory crests on adjacent peniplates; these surely correspond to lines demarcating growth phases of the motile dinoflagellate.
The archaeopyle is formed by loss of all the apical paraplates; its angular margin has deep parasutural notches (Pl. 5, Fig. 16).
Dimensions:
Holotype: length (apex missing) 26 µm, breadth 29 µm, height of crests 0.5-1.5 µm, width 0.5-1.0 µm.
Range of 61 measurable specimens: length (apex missing) 25-37 µm, mean 31 µm; breadth 25-37 µm, mean 29 µm; height of crests 0.5-2.0 µm; width 0.5-1.0 µm.
Affinities: (p. 98):
The low, spine-supported crests distinguish this from all other species of Alisocysta. A. ornata (Cookson and Eisenack, 1965) Stover and Evitt 1978 and A. circumtabulata (Drugg 1967) Stover and Evitt 1978 are similar, but differ respectively in having smooth, distally tapering penitabular ridges or high, membranous penitabular crests. The specimens illustrated by Leopold & Tschudy (1965, Figs. 237, 238) appear similar in size and morphology to those observed.