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Hystrichosphaeridium rhopalophorum
Hystrichosphaeridium rhopalophorum Valensi, 1955
Now Exochosphaeridium. Originally Hyxtrichosphaeridium, subsequently (and now) Exochosphaeridium.
Holotype: Valensi, 1955, fig.1C
Age: Late Cretaceous
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Original description: [Valensi, 1955] (translated from French):
Holotype: Cretaceous flint from Venesmes.
The shell, with a slightly ellipsoidal outline, is bristling with a large number of processes whose length is of the order of a third of its major axis. These club-shaped processes are inserted into the shell by their swollen part. The base of these processes is very strongly widened, conical or potbellied; their narrowed extremity generally originates at a third of their length; sometimes, it simply extends the base while gradually thinning, sometimes, on the contrary, it separates from it by a more or less pronounced constriction. The processes are hollow and their cavity does not give the impression of communicating with that of the shell.
The surface of the shell is finely granular and the color dark yellow. The wingspan of Hystrichosphaeridium rhopalophorum is 47 to 50 μ, the major axis of the shell alone measures 32 μ and its minor axis 26 μ. The processes are about ten μ long.
Hystrichosphaeridium rhopalophorum is reminiscent of Micrhystridium lagynophorum from the Middle Jurassic of Normandy by the shape of its processes. However, it differs in its size (47 to 50 μ wingspan, instead of 30 to 33), the greater density of its processes of circular or elliptical but never polygonal section and the absence of membranous crests that connect them.
The same Venesmes flint provided me with two other specimens of this species.
Now Exochosphaeridium. Originally Hyxtrichosphaeridium, subsequently (and now) Exochosphaeridium.
Holotype: Valensi, 1955, fig.1C
Age: Late Cretaceous
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Original description: [Valensi, 1955] (translated from French):
Holotype: Cretaceous flint from Venesmes.
The shell, with a slightly ellipsoidal outline, is bristling with a large number of processes whose length is of the order of a third of its major axis. These club-shaped processes are inserted into the shell by their swollen part. The base of these processes is very strongly widened, conical or potbellied; their narrowed extremity generally originates at a third of their length; sometimes, it simply extends the base while gradually thinning, sometimes, on the contrary, it separates from it by a more or less pronounced constriction. The processes are hollow and their cavity does not give the impression of communicating with that of the shell.
The surface of the shell is finely granular and the color dark yellow. The wingspan of Hystrichosphaeridium rhopalophorum is 47 to 50 μ, the major axis of the shell alone measures 32 μ and its minor axis 26 μ. The processes are about ten μ long.
Hystrichosphaeridium rhopalophorum is reminiscent of Micrhystridium lagynophorum from the Middle Jurassic of Normandy by the shape of its processes. However, it differs in its size (47 to 50 μ wingspan, instead of 30 to 33), the greater density of its processes of circular or elliptical but never polygonal section and the absence of membranous crests that connect them.
The same Venesmes flint provided me with two other specimens of this species.