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Palaeogene
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Pontosphaera (21)
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Pontosphaera
print this pageDescription
Zygodiscales
Thu, 11/10/2007 - 14:20 — Jeremy Young
Order ZYGODISCALES Young & Bown 1997
Taxa included: The extant families Helicosphaeraceae and Pontosphaeraceae and extinct Family Zygodiscaceae. These show highly variable shape, but similar structure, and there is strong palaeontological evidence for their evolutionary connections (Romein 1979; Aubry 1989).
Coccolith structure: V-units form outer rim; in Pontosphaeraceae, this is a narrow cycle of anticlockwise-imbricating elements, in the Helicosphaeraceae, a helical flange. The R-units form a proximal plate of rather regular, inward-growing elements and a distal blanket, which typically appears as a mass of minute, tangentially-elongated crystallites. Growth does not occur downwards from the proto-coccolith ring and so the alternating belt of V-R nuclei remains clearly visible on the proximal surface.
Life-cycles and culture studies: Helicosphaera carteri and H. wallichii have been cultured repeatedly (Inouye pers. comm.; Probert & Houdan 2004) and Scyphosphaera apsteinii once (Probert & Houdan 2004). No life-cycle transitions have been observed in these cultures, but combination coccospheres have been observed for Helicosphaera (Cros et al. 2000; Geisen et al. 2002). These indicate that the haploid phase forms holococcoliths with distinctive rhomboid-array ultrastructure (formerly included in the genus Syracolithus).
Comment and discussion:Helicosphaera sellii
Sun, 18/11/2007 - 19:16 — Anonymous
Helicosphaera sellii (Bukry and Bramlette, 1969) Jafar and Martini, 1975 [Helicopontosphaera]
Description: Like H. carteri but pores large.
Remarks:
Range: NN12 to 19. Last occurrence has been used in some zonatons but is rather diachronous
Original description:
Variant: H. omanica Sato, Kameo and Takayama, 1991 - bar missing, ? dissolved. Also similar to H. neogranulata.
Comment and discussion:Helicosphaera perch-nielseniae
Sun, 18/11/2007 - 19:00 — Anonymous
Helicosphaera perch-nielseniae (Haq, 1971) Jafar and Martini, 1975 [Helicopontosphaera]
Description: Like H. obliqua but pores narrower and shape more oblong, less spindle-like (N.B. criteria for separating H. obliqua and H. perch-nielseniae vary between authors).
Range: NP23 to NN6.
Original description:
Variant: H. elongata Theodoridis, 1984 - more elongate and with more rectangular outline.
Comment and discussion:Pontosphaera multipora
Sun, 18/11/2007 - 18:47 — AnonymousPontosphaera multipora (Kamptner, 1948) Roth, 1970 [Discolithus]
Description: Rim elevated, 3 or more several cycles of pores.
Remarks:
Range: Palaeogene to NN21.
Original description:
Comment and discussion:Pontosphaera discopora
Sun, 18/11/2007 - 18:45 — AnonymousPontosphaera discopora Schiller, 1925
Description: Rim elevated, 3 or more several cycles of pores.
Remarks:
Range: Palaeogene to NN21.
Original description:
Comment and discussion:Scyphosphaera
Sun, 18/11/2007 - 20:30 — Anonymous
Genus Scyphosphaera Lohmann, 1902
Description: Coccospheres with Pontosphaera-like body coccoliths and equatorial coccoliths with rims elevated into vase-like structures (lopadoliths).
Remarks: In fossil assemblages, only lopadoliths are assigned to Scyphosphaera.
Numerous Neogene species have been described, often based on subtle variations in outline, but since the single modern species S. apsteinii shows considerable variation in lopadolith outline a broader species concept seems justified. Three main species are certainly separable; S. apsteinii, S. pulcherimma and S. globulata. The table below summarises the morphotypes and for each one possilbe synonyms re listed on the species page. See also Jafar (1975), Perch-Nielsen (1984) Aubry (1990) and Siesser (1998).Original description:
apsteinii 
pulcherrima 
globulata 
tubifera 
intermedia
ventriosa 
lagena
cylindrica Comment and discussion:Braarudosphaera
Thu, 11/10/2007 - 14:20 — Jeremy YoungBraarudosphaera Deflandre 1947 [Pontosphaera]
Description: Pentaliths approximately pentagonal, sutures go to edges of pentagon. NB In Micrantholithus sutures go to vertices of the pentagon.
Remarks:
Type species: Pontosphaera bigelowii Gran & Braarud 1935.
Range: Cretaceous to Recent.
Original description:
Comment and discussion:
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