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Litosphaeridium fucosum
Litosphaeridium fucosum (Valensi, 1955a, p.40; text-fig.2b) Masure in Fauconnier and Masure, 2004, p.378. Holotype: Valensi, 1955a, text-fig.2b; Fauconnier and Masure, pl.52, figs.8–11. Originally Micrhystridium, subsequently Hystrichosphaeridium, thirdly Polysphaeridium?, fourthly Dapsilidinium?, fifthly (and now) Litosphaeridium. Taxonomic junior synonyms (at specific rank): Hystrichosphaeridium tubiferum subsp. brevispinum, according to Below (1982c, p.29); Hystrichosphaeridium (as and now Litosphaeridium) arundum, according to Below (1982c,
p.29) — however, Lentin and Williams (1985, p.190,227) retained Hystrichosphaeridium tubiferum subsp. brevispinum and Litosphaeridium arundum. Age: Late Cretaceous.
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Original description: [Valensi, 1955] (translated from French):
Micrhystridium fucosum n. sp.
Fig. 2 B.
Holotype (unique): Cretaceous flint from Venesmes.
The ovoid shell bears about twenty tube-like processes, the length of which is between one-third and one-half of its diameter. These tubes are hollow, circular in cross-section, and their cavity does not appear to communicate with that of the shell; slightly widened at their base, they flare slightly at their tip. The surface of the shell is granular and light brown in color.
The shell alone measures 20 to 24 μ, the processes 7 to 10 μ, and the entire span 30 to 35 μ. Despite the absence of spines on the edges of the terminal funnel of the processes, Micrhystridium fucosum is unquestionably a "Tubifer", but its small size and short processes distance it from Hystrichosphaeridum tubifer um and its more than double size, from Micrhystridium paulinae VAL., from the Jurassic.
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Emendation: (Fauconnier and Masure, 2004, p. 378) (translated from French):
Amended diagnosis: Chorate cyst, whose central body is subspherical to ellipsoid in shape and subcircular to oval in ambitus. The wall is formed of an endophragm and a periphragm adjacent between the processes. The surface of the central body is granular to finely reticulated. The periphragm alone forms the tubular, hollow, intratabular processes (1 to 3-4 depending on the paraplates). Their truncated or slightly flared distal ends are bordered by a serrate rim. The cingulate processes (1 or 2 per paraplate) are thinner than the pre- and postcingulates and open distally. The distribution of the processes indicates a gonyaulacoid paratabulation (3-4', 5-6", 6c, 6'", 1"", Xs). The archaeopyle is apical, type (tA).
The operculum is adnate.
BELOW (1982c, p. 29) considers Micrhystridium fucosum VALENSI, 1955a to be an older synonym of Hystrichosphaeridium arundum. EISENACK
& COOKSON, 1960, DAVEY & VWILLIAMS (1969, p. 6) reservedly assign M. fucosum VALENSI, 1955a to the genus Polysphaeridium DAVEY & WILLIAMS, 1966b emend. BUJAK et al., 1980. LENTIN & WILLIAMS (1981, p. 69) assign probably the species fucsum to the genus Dapsilidinium BuJAK et al., 1980. Litosphaeridium fucosum and Litosphaeridium arundum are very close morphologically.
Nevertheless, they can be distinguished by the length of their processes. Compared to the equatorial diameter of the central body, the processes are shorter in L. arundum (R 0.23) than in L. fucosum (R = 0.43-0.45). These two species are likely the extremes of the same complex.
p.29) — however, Lentin and Williams (1985, p.190,227) retained Hystrichosphaeridium tubiferum subsp. brevispinum and Litosphaeridium arundum. Age: Late Cretaceous.
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Original description: [Valensi, 1955] (translated from French):
Micrhystridium fucosum n. sp.
Fig. 2 B.
Holotype (unique): Cretaceous flint from Venesmes.
The ovoid shell bears about twenty tube-like processes, the length of which is between one-third and one-half of its diameter. These tubes are hollow, circular in cross-section, and their cavity does not appear to communicate with that of the shell; slightly widened at their base, they flare slightly at their tip. The surface of the shell is granular and light brown in color.
The shell alone measures 20 to 24 μ, the processes 7 to 10 μ, and the entire span 30 to 35 μ. Despite the absence of spines on the edges of the terminal funnel of the processes, Micrhystridium fucosum is unquestionably a "Tubifer", but its small size and short processes distance it from Hystrichosphaeridum tubifer um and its more than double size, from Micrhystridium paulinae VAL., from the Jurassic.
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Emendation: (Fauconnier and Masure, 2004, p. 378) (translated from French):
Amended diagnosis: Chorate cyst, whose central body is subspherical to ellipsoid in shape and subcircular to oval in ambitus. The wall is formed of an endophragm and a periphragm adjacent between the processes. The surface of the central body is granular to finely reticulated. The periphragm alone forms the tubular, hollow, intratabular processes (1 to 3-4 depending on the paraplates). Their truncated or slightly flared distal ends are bordered by a serrate rim. The cingulate processes (1 or 2 per paraplate) are thinner than the pre- and postcingulates and open distally. The distribution of the processes indicates a gonyaulacoid paratabulation (3-4', 5-6", 6c, 6'", 1"", Xs). The archaeopyle is apical, type (tA).
The operculum is adnate.
BELOW (1982c, p. 29) considers Micrhystridium fucosum VALENSI, 1955a to be an older synonym of Hystrichosphaeridium arundum. EISENACK
& COOKSON, 1960, DAVEY & VWILLIAMS (1969, p. 6) reservedly assign M. fucosum VALENSI, 1955a to the genus Polysphaeridium DAVEY & WILLIAMS, 1966b emend. BUJAK et al., 1980. LENTIN & WILLIAMS (1981, p. 69) assign probably the species fucsum to the genus Dapsilidinium BuJAK et al., 1980. Litosphaeridium fucosum and Litosphaeridium arundum are very close morphologically.
Nevertheless, they can be distinguished by the length of their processes. Compared to the equatorial diameter of the central body, the processes are shorter in L. arundum (R 0.23) than in L. fucosum (R = 0.43-0.45). These two species are likely the extremes of the same complex.