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Pervosphaeridium truncatum
Pervosphaeridium truncatum (Davey, 1969) Below, 1982; emend. Masure, 1988; emend. Harker and Sarjeant in Harker et al., 1990
Originally Exochosphaeridium striolatum var. truncatum, subsequently Exochosphaeridium striolatum ssp. truncatum, thirdly Exochosphaeridium? truncatum, fourthly (and now) Pervosphaeridium truncatum.
Holotype: Davey, 1969, pl.7, fig.2
Locus typicus: Escalles, France
Stratum typicum: Cenomanian
Original diagnosis: Davey, 1969, p. 164-165: Exochosphaeridium striolatum ssp. truncatum
A variety of E. striolatum possessing subspherical to ovoidal shell; shell wall fibrous or lightly pitted. Processes numerous, typically fibrous and blunted distally, slender or subtriangular, rarely branched. Apical process large, often foliate. Precingular archaeopyle, commonly present, formed by loss of two plate areas, rarely one.
Dimensions: diameter of central body 34 (56.I) 81 µm, maximum length of processes 6 (17.8) 27 µm.
Original descripition: Davey, 1969, p. 165: Exochosphaeridium striolatum ssp. truncatum
The shell possesses a moderately thick wall (c. 1 µm) but it is quite often distorted, especially when an archaeopyle is developed. The shell surface (periphragm) is typically fibrous; the fibres pass down the length of the processes onto the shell surface and, there, join up with similar fibres from adjacent processes. Some specimens are less conspicuously fibrous, the fibres being apparent near the bases of the processes and only extending a little way onto the shell surface. The remainder of the shell surface in these forms is lightly pitted. The processes may be fairly slender to subtriangular and are occasionally joined proximally. A small number of processes are subdivided medially. The processes are typically truncated distally but may be slightly bulbous. Process alignment was not observed. The apical process is larger than the other processes and often foliate; the endophragm occasionally forms a small apical bulge beneath it.
Archaeopyle: typically formed by the removal of two precingular plates, as is apparent by its shape. Rarely only one plate is lost. Detached opercula consisting of two precingular plates have been located.
Emended diagnosis: Masure, 1988, p.129
Proximochorate, two-layered dinoflagellate cyst with sub.pheroidal central body and fibrous, lightly pitted periphragm. Processes intratabular, hollow, fibrous with broad bases, blunted distally, slender, some joined proximally Apical and antapical processes well developed. Gonyaulacoid paratabulation processes represent 1-?2 preapicals, 4 apicals, 6 precingulars, 6 cingulars, X sulcals, 5-6 postcingulars, ? 1 posterior intercalary, 1 antapical. Precingular archeopyle, type 2P 3-4.
Emended description: Masure, 1988, p. 129
The processes are intratabular, with one or more than one for each paraplate. The processes of the post-cingular paraplate (III / IV) may form a penitabular complex. with their broad bases joined proximally. The preapical process is distinctive; the antapical Y is well developed.
Emended diagnosis: Harker, Sarjeant and Caldwell, 1990, p. 73-74
Proximochorate cyst, with radius of endocoel: radius overall within the range 0.6-0.8. Ambitus spheroidal to ovoidal. Periphragm composed of fibres producing a meshwork that covers the shagreenate endophragm; total phragma thickness around 1-1.5 µm. Numerous short, nontabular processes arise at the confluence of several fibres (a feature best seen under scanning electron microscopy: see Pl. 3, Fig. 12). Processes slender, tapering to sub-triangular; blunted; bulbous, branched or recurved distally; often connected proximally to adjacent processes by low fibrous crests. Apical process usually large and foliate, arising from a small apical bulge. Cingulum sometimes indicated by a parallel alignment of processes about the equatorial region (Pl. 3, Fig. 11). Archaeopyle adjacent and anterior to the cingulum on the dorsal surface and formed by loss of two precingular
paraplates (Pl. 3, Fig. 10).
Affinities:
Masure, 1988, p.129: P trunratum differs from other species of the genus in having some processes joined proximally. The archeopyle formula of the genus Pervosphaeridium is 2P (Yun, 1981). Below (1981, p. 60) specified that the archeopyle of Pervosphaeridium paucispinum was 2P 3-4. P. truncatum and P. paucispinum appear to have 2P 3-4 archeopyle formula.
Originally Exochosphaeridium striolatum var. truncatum, subsequently Exochosphaeridium striolatum ssp. truncatum, thirdly Exochosphaeridium? truncatum, fourthly (and now) Pervosphaeridium truncatum.
Holotype: Davey, 1969, pl.7, fig.2
Locus typicus: Escalles, France
Stratum typicum: Cenomanian
Original diagnosis: Davey, 1969, p. 164-165: Exochosphaeridium striolatum ssp. truncatum
A variety of E. striolatum possessing subspherical to ovoidal shell; shell wall fibrous or lightly pitted. Processes numerous, typically fibrous and blunted distally, slender or subtriangular, rarely branched. Apical process large, often foliate. Precingular archaeopyle, commonly present, formed by loss of two plate areas, rarely one.
Dimensions: diameter of central body 34 (56.I) 81 µm, maximum length of processes 6 (17.8) 27 µm.
Original descripition: Davey, 1969, p. 165: Exochosphaeridium striolatum ssp. truncatum
The shell possesses a moderately thick wall (c. 1 µm) but it is quite often distorted, especially when an archaeopyle is developed. The shell surface (periphragm) is typically fibrous; the fibres pass down the length of the processes onto the shell surface and, there, join up with similar fibres from adjacent processes. Some specimens are less conspicuously fibrous, the fibres being apparent near the bases of the processes and only extending a little way onto the shell surface. The remainder of the shell surface in these forms is lightly pitted. The processes may be fairly slender to subtriangular and are occasionally joined proximally. A small number of processes are subdivided medially. The processes are typically truncated distally but may be slightly bulbous. Process alignment was not observed. The apical process is larger than the other processes and often foliate; the endophragm occasionally forms a small apical bulge beneath it.
Archaeopyle: typically formed by the removal of two precingular plates, as is apparent by its shape. Rarely only one plate is lost. Detached opercula consisting of two precingular plates have been located.
Emended diagnosis: Masure, 1988, p.129
Proximochorate, two-layered dinoflagellate cyst with sub.pheroidal central body and fibrous, lightly pitted periphragm. Processes intratabular, hollow, fibrous with broad bases, blunted distally, slender, some joined proximally Apical and antapical processes well developed. Gonyaulacoid paratabulation processes represent 1-?2 preapicals, 4 apicals, 6 precingulars, 6 cingulars, X sulcals, 5-6 postcingulars, ? 1 posterior intercalary, 1 antapical. Precingular archeopyle, type 2P 3-4.
Emended description: Masure, 1988, p. 129
The processes are intratabular, with one or more than one for each paraplate. The processes of the post-cingular paraplate (III / IV) may form a penitabular complex. with their broad bases joined proximally. The preapical process is distinctive; the antapical Y is well developed.
Emended diagnosis: Harker, Sarjeant and Caldwell, 1990, p. 73-74
Proximochorate cyst, with radius of endocoel: radius overall within the range 0.6-0.8. Ambitus spheroidal to ovoidal. Periphragm composed of fibres producing a meshwork that covers the shagreenate endophragm; total phragma thickness around 1-1.5 µm. Numerous short, nontabular processes arise at the confluence of several fibres (a feature best seen under scanning electron microscopy: see Pl. 3, Fig. 12). Processes slender, tapering to sub-triangular; blunted; bulbous, branched or recurved distally; often connected proximally to adjacent processes by low fibrous crests. Apical process usually large and foliate, arising from a small apical bulge. Cingulum sometimes indicated by a parallel alignment of processes about the equatorial region (Pl. 3, Fig. 11). Archaeopyle adjacent and anterior to the cingulum on the dorsal surface and formed by loss of two precingular
paraplates (Pl. 3, Fig. 10).
Affinities:
Masure, 1988, p.129: P trunratum differs from other species of the genus in having some processes joined proximally. The archeopyle formula of the genus Pervosphaeridium is 2P (Yun, 1981). Below (1981, p. 60) specified that the archeopyle of Pervosphaeridium paucispinum was 2P 3-4. P. truncatum and P. paucispinum appear to have 2P 3-4 archeopyle formula.