Back
Exochosphaeridium truncatum
Exochosphaeridium truncatum (Davey, 1969) Stover and Evitt, 1978
Now Pervosphaeridium truncatum. Originally Exochosphaeridium striolatum var. truncatum, subsequently Exochosphaeridium striolatum ssp. truncatum, thirdly Exochosphaeridium? truncatum, fourthly (and now) Pervosphaeridium truncatum.
Stover and Evitt, 1978, questionably included this species in Exochosphaeridium.
Holotype: Davey, 1969, pl.7, fig.2
Age: Cenomanian
Original diagnosis: Davey, 1969, p. 164-165
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 Ám, maximum length of processes 6(17.8)27 Ám.
Original descrpition: Davey, 1969, p. 165
The shell possesses a moderately thick wall (c. 1 Ám) but it is quite often distorted, especially when an archaeopyle is developed. The shcll 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 proccsses. 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 othcr processes and often foliate; the endophragm occasionally forms a small apical bulge beneath it. The archaeopyle is 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.
Now Pervosphaeridium truncatum. Originally Exochosphaeridium striolatum var. truncatum, subsequently Exochosphaeridium striolatum ssp. truncatum, thirdly Exochosphaeridium? truncatum, fourthly (and now) Pervosphaeridium truncatum.
Stover and Evitt, 1978, questionably included this species in Exochosphaeridium.
Holotype: Davey, 1969, pl.7, fig.2
Age: Cenomanian
Original diagnosis: Davey, 1969, p. 164-165
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 Ám, maximum length of processes 6(17.8)27 Ám.
Original descrpition: Davey, 1969, p. 165
The shell possesses a moderately thick wall (c. 1 Ám) but it is quite often distorted, especially when an archaeopyle is developed. The shcll 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 proccsses. 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 othcr processes and often foliate; the endophragm occasionally forms a small apical bulge beneath it. The archaeopyle is 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.