Back
Downiesphaeridium polyacanthum
Downiesphaeridium polyacanthum (Gitmez, 1970) Islam, 1993
Originally Cleistosphaeridium, subsequently Cleistosphaeridium?, thirdly Downiesphaeridium.
Taxonomic senior synonym: Hystrichosphaeridium (now Downiesphaeridium) polytrichum, according to Masure in Fauconnier and Masure (2004, p.196).
Taxonomic senior synonym: Baltisphaeridium (as Cleistosphaeridium) iaculigerum, according to Brenner (1988, p.42) - however, neither Islam (1993, p.84), who retained Downiesphaeridium polyacanthum, nor Masure in Fauconnier and Masure (2004, p.196) followed this synonymy.
Holotype: Gitmez, 1970, pl.12, fig.10, text-fig.22B
Locus typicus: Kimmeridge Clay from between the Ringstead Waxy Clay and the Coral bed, Ringstead Bay, Dorset (RB 218), England
Stratum typicum: Early Kimmeridgian
Translation Courtinat, 1989: LPP
Original diagnosis: Gitmez, 1970, p.284: Cleistosphaeridium polyacanthum
A Cleistosphaeridium having an ellipsoidal to ovoidal shell bearing numerous processes (50-70 in number). All processes of approximately same length (not less than half of the shell length), simple, straight, hollow and acuminate. Shell surface smooth. Apical archaeopyle sometimes present.
Dimensions: Holotype: shell length 40 Ám, breadth 30 Ám; length of the processes 20-22 Ám. Range of the English specimens (5 specimens measured): shell length 33-42 Ám, breadth 28-35 Ám; French specimens (4 specimens measured): shell length 30-45 Ám, breadth 25-38 Ám; length of the processes 16-20 Ám.
Original description: Gitmez, 1970, p.286: Cleistosphaeridium polyacanthum
This chorate cyst has processes in variable number, 50-70, their cavity directly connected to the shell interior. There are no fields or plates identifiable on the shell.
Affinities:
Gitmez, 1970, p.284: Cleistosphaeridium polyacanthum
This new form of Cleistosphaeridium should be placed morphologically between C. ehrenbergi and C. polytrichum. It differs from them consistently in shell shape and in the number of the processes. These three species do not seem to be part of a continuously varying plexus, at least at this horizon, since intermediate forms were not encountered (Table 5).
C. polyacanthum is comparable with C. flexuosum, which was recorded from Cenomanian of England by Davey, Downie, Sarjeant and Williams (1966), in its ovoidal shape and simple acuminate processes in large number. Since the processes of C. flexuosum are slightly fibrous and always flexuous, this new species is different; moreover, archaeopyle formation was not observed in C. flexuosum.
Courtinat, 1989, p.167: This species is distinguished from C. deflandrei in the slightly longer processes. The number of processes seems identical in both species. Possibly the two species are synonymous.
Originally Cleistosphaeridium, subsequently Cleistosphaeridium?, thirdly Downiesphaeridium.
Taxonomic senior synonym: Hystrichosphaeridium (now Downiesphaeridium) polytrichum, according to Masure in Fauconnier and Masure (2004, p.196).
Taxonomic senior synonym: Baltisphaeridium (as Cleistosphaeridium) iaculigerum, according to Brenner (1988, p.42) - however, neither Islam (1993, p.84), who retained Downiesphaeridium polyacanthum, nor Masure in Fauconnier and Masure (2004, p.196) followed this synonymy.
Holotype: Gitmez, 1970, pl.12, fig.10, text-fig.22B
Locus typicus: Kimmeridge Clay from between the Ringstead Waxy Clay and the Coral bed, Ringstead Bay, Dorset (RB 218), England
Stratum typicum: Early Kimmeridgian
Translation Courtinat, 1989: LPP
Original diagnosis: Gitmez, 1970, p.284: Cleistosphaeridium polyacanthum
A Cleistosphaeridium having an ellipsoidal to ovoidal shell bearing numerous processes (50-70 in number). All processes of approximately same length (not less than half of the shell length), simple, straight, hollow and acuminate. Shell surface smooth. Apical archaeopyle sometimes present.
Dimensions: Holotype: shell length 40 Ám, breadth 30 Ám; length of the processes 20-22 Ám. Range of the English specimens (5 specimens measured): shell length 33-42 Ám, breadth 28-35 Ám; French specimens (4 specimens measured): shell length 30-45 Ám, breadth 25-38 Ám; length of the processes 16-20 Ám.
Original description: Gitmez, 1970, p.286: Cleistosphaeridium polyacanthum
This chorate cyst has processes in variable number, 50-70, their cavity directly connected to the shell interior. There are no fields or plates identifiable on the shell.
Affinities:
Gitmez, 1970, p.284: Cleistosphaeridium polyacanthum
This new form of Cleistosphaeridium should be placed morphologically between C. ehrenbergi and C. polytrichum. It differs from them consistently in shell shape and in the number of the processes. These three species do not seem to be part of a continuously varying plexus, at least at this horizon, since intermediate forms were not encountered (Table 5).
C. polyacanthum is comparable with C. flexuosum, which was recorded from Cenomanian of England by Davey, Downie, Sarjeant and Williams (1966), in its ovoidal shape and simple acuminate processes in large number. Since the processes of C. flexuosum are slightly fibrous and always flexuous, this new species is different; moreover, archaeopyle formation was not observed in C. flexuosum.
Courtinat, 1989, p.167: This species is distinguished from C. deflandrei in the slightly longer processes. The number of processes seems identical in both species. Possibly the two species are synonymous.