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Endoscrinium tabulatum
Endoscrinium tabulatum Miles, 1990, p.81-82, pl.1, figs.1-12; text-figs.3A-B. Holotype: Miles, 1990, pl.1, figs.1-6. Questionable assignment: Riding and Fensome (2003, p.23); these authors considered that the species may belong to the genus Impagidinium. Age: Late Albian.
Original diagnosis: Miles, 1990, p. 81-82
Small, cavate dinoflagellate cyst showing dorso-ventral compression; outline in dorso-ventral view is subcircular. Inner body consists of a psilate endophragm, compressed dorso-ventrally, subcircular in outline and of a diameter approximately one-half that of the periphragm. Endophragm is attached to the periphragm in the mid-ventral region. The periphragm is smooth, and bears low but distinct ridges that define a gonyaulacoid paratabulation (Taylor/Evitt equivalents in parentheses): xpr, 4" (A-C, lu), 6" (li, 2-6), 6c (au, b-e, fi), 5""" (II-VI), 1p (X), 1"""" (Y), xs (including Z); see Text-Figure 2. No sulcal paratabulation is evident, and the boundaries between the parasulcus (Z) and paraplates 1""" (II), 1p (X), 6""" (Vl) and 6c (fi) are partially or completely suppressed. The paracingulum is laevorotatory and is offset by approximately its own width. Paraplates 1" (lu) and 6" (li) have no common boundary, being separated by paraplate 4" (A) . The adcingular boundary of paraplate 6" (li) is longer than its contact with paraplate 4" (A), giving a trapezoidal shape. Paraplate 1"""" (Y) contacts the sulcus (Z) and paraplates 1p (X), 2""" (III), 3""" (IV), 4""" (V) and 5""" (VI). This distribution of the antapical series and the sulcal arrangement are typical of the S-type sexiform group of Evitt (1985).
Archeopyle is precingular, formed by the loss of paraplate 3" (4); the endo- and periarcheopyles are congruent. Measurements. Minimum (average) maximum: overall length 38(43)52 Ám, overall width 38(43)51 Ám, length of innerbody 21(26)31 Ám, width of innerbody 19(23)30 Ám (based on 15 well-preserved and well-orientated specimens).
Affinities:
Miles, 1990, p. 82: The circumcavate wall relationship, subcircular shape, Type P precingular archeopyle, and paratabulation indicated by low ridges are features typical of the genus Endoscrinum Klement 1960, to which this species is assigned.
The separation of paraplates 1" (lu) and 6" (li) is a feature shared with species of the non-cavate genus Impagidinium Stover and Evitt 1978. There is some similarity with species of Thalassiphora Eisenack and Gocht 1960 emend. Gocht 1968. However, Endoscrinium tabulatum lacks the prominent opening in the ventral surface of the periphragm seen in Thalassiphora pelagica (Eisenack 1954) Eisenack & Gocht 1960 and T. delicata Williams and Downie 1966 emend. Eaton 1976. In addition, E. tabulatum lacks the distinctive paratabulation of T. delicata as illustrated by Eaton (1976, 1980).
Original diagnosis: Miles, 1990, p. 81-82
Small, cavate dinoflagellate cyst showing dorso-ventral compression; outline in dorso-ventral view is subcircular. Inner body consists of a psilate endophragm, compressed dorso-ventrally, subcircular in outline and of a diameter approximately one-half that of the periphragm. Endophragm is attached to the periphragm in the mid-ventral region. The periphragm is smooth, and bears low but distinct ridges that define a gonyaulacoid paratabulation (Taylor/Evitt equivalents in parentheses): xpr, 4" (A-C, lu), 6" (li, 2-6), 6c (au, b-e, fi), 5""" (II-VI), 1p (X), 1"""" (Y), xs (including Z); see Text-Figure 2. No sulcal paratabulation is evident, and the boundaries between the parasulcus (Z) and paraplates 1""" (II), 1p (X), 6""" (Vl) and 6c (fi) are partially or completely suppressed. The paracingulum is laevorotatory and is offset by approximately its own width. Paraplates 1" (lu) and 6" (li) have no common boundary, being separated by paraplate 4" (A) . The adcingular boundary of paraplate 6" (li) is longer than its contact with paraplate 4" (A), giving a trapezoidal shape. Paraplate 1"""" (Y) contacts the sulcus (Z) and paraplates 1p (X), 2""" (III), 3""" (IV), 4""" (V) and 5""" (VI). This distribution of the antapical series and the sulcal arrangement are typical of the S-type sexiform group of Evitt (1985).
Archeopyle is precingular, formed by the loss of paraplate 3" (4); the endo- and periarcheopyles are congruent. Measurements. Minimum (average) maximum: overall length 38(43)52 Ám, overall width 38(43)51 Ám, length of innerbody 21(26)31 Ám, width of innerbody 19(23)30 Ám (based on 15 well-preserved and well-orientated specimens).
Affinities:
Miles, 1990, p. 82: The circumcavate wall relationship, subcircular shape, Type P precingular archeopyle, and paratabulation indicated by low ridges are features typical of the genus Endoscrinum Klement 1960, to which this species is assigned.
The separation of paraplates 1" (lu) and 6" (li) is a feature shared with species of the non-cavate genus Impagidinium Stover and Evitt 1978. There is some similarity with species of Thalassiphora Eisenack and Gocht 1960 emend. Gocht 1968. However, Endoscrinium tabulatum lacks the prominent opening in the ventral surface of the periphragm seen in Thalassiphora pelagica (Eisenack 1954) Eisenack & Gocht 1960 and T. delicata Williams and Downie 1966 emend. Eaton 1976. In addition, E. tabulatum lacks the distinctive paratabulation of T. delicata as illustrated by Eaton (1976, 1980).