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Valensiella amandopolitana
From Fensome et al., 2019:
Valensiella? amandopolitana (Valensi, 1955b, p.590, pl.2, fig.7; pl.5, fig.2) Eisenack, 1963a, p.102.
Holotype: Valensi, 1955b, pl.2, fig.7.
Originally Membranilarnax, subsequently Favilarnax, thirdly Valensiella, fourthly (and now) Valensiella?.
Questionable assignment: Stover and Evitt (1978, p.86).
Age: Middle Jurassic.
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Valansi, 1955b: Translation PKB 2024
Holotype: Jurassic selex of the venesmes (Pl, II, Fig. 7)
The shell is ovoid or ellipsoidal in shape and its equatorial section is circular. Its surface is divided into a small number of polygonal fields (10 to 20 per hemisphere) by a system of membranous ridges supported by T-shaped processes: the branches of these Ts, horizontal and straight, are generally three in number and anastomose with each other. A thin film sometimes seems to envelop the shell.
The processes are almost always shorter at one or both poles, but the fields occupying these poles do not differ from the others. The colour is always dark brown and the surface of the shell is granular.
The dimensions, including the processes, are 21 to 33 µm for the minor axis and 23 to 37 µm for the major axis, the most frequent dimensions are around 25 µm for the minor axis and 30 for the major axis. The processes are 2 to 4 µm long and there are 14 to 30 peripheral processes in optical section.
M. amandopolitanum is the most common and characteristic microorganism of the Jurassic flints of the Magdalenian of Saint-Amand. Rarely deformed or damaged, it is very easily recognizable, because all its specimens look alike and have a family air, which allows them to be identified at first glance and without hesitation.
I found about fifty individuals, some variations have few processi (14 peripheral processes) and relatively longer: others, more numerous processi (22 periperial processes) and relatively shorter, A single individual has many small polygonal fields and often rectangular outline.
M. amandopolitanum belongs to a fairly common morphology represented by Cymatiosphaera pavimenta Defl. from the Silurian and Cymatiosphaera eupeplos Val. From the Middle Jurassic, it even recalls quite closely the C. eupeplos that I drew (L. Valensi, 1953, Pl. VIII, Fig. 38). It differs, however, from these Cymatiosphaera by its generally larger size and by the presence of an external film, which has often disappeared as a result of fossilization. The presence of this film brings Membranitarnax amandopolitanum closer to Membranitarnax ovulum, but in the latter the dimensions are double and the shell has an opening at one end which does not exist in M. amandopolitanum.
Valensiella? amandopolitana (Valensi, 1955b, p.590, pl.2, fig.7; pl.5, fig.2) Eisenack, 1963a, p.102.
Holotype: Valensi, 1955b, pl.2, fig.7.
Originally Membranilarnax, subsequently Favilarnax, thirdly Valensiella, fourthly (and now) Valensiella?.
Questionable assignment: Stover and Evitt (1978, p.86).
Age: Middle Jurassic.
---------------------------------------------------------------------------------------------------
Valansi, 1955b: Translation PKB 2024
Holotype: Jurassic selex of the venesmes (Pl, II, Fig. 7)
The shell is ovoid or ellipsoidal in shape and its equatorial section is circular. Its surface is divided into a small number of polygonal fields (10 to 20 per hemisphere) by a system of membranous ridges supported by T-shaped processes: the branches of these Ts, horizontal and straight, are generally three in number and anastomose with each other. A thin film sometimes seems to envelop the shell.
The processes are almost always shorter at one or both poles, but the fields occupying these poles do not differ from the others. The colour is always dark brown and the surface of the shell is granular.
The dimensions, including the processes, are 21 to 33 µm for the minor axis and 23 to 37 µm for the major axis, the most frequent dimensions are around 25 µm for the minor axis and 30 for the major axis. The processes are 2 to 4 µm long and there are 14 to 30 peripheral processes in optical section.
M. amandopolitanum is the most common and characteristic microorganism of the Jurassic flints of the Magdalenian of Saint-Amand. Rarely deformed or damaged, it is very easily recognizable, because all its specimens look alike and have a family air, which allows them to be identified at first glance and without hesitation.
I found about fifty individuals, some variations have few processi (14 peripheral processes) and relatively longer: others, more numerous processi (22 periperial processes) and relatively shorter, A single individual has many small polygonal fields and often rectangular outline.
M. amandopolitanum belongs to a fairly common morphology represented by Cymatiosphaera pavimenta Defl. from the Silurian and Cymatiosphaera eupeplos Val. From the Middle Jurassic, it even recalls quite closely the C. eupeplos that I drew (L. Valensi, 1953, Pl. VIII, Fig. 38). It differs, however, from these Cymatiosphaera by its generally larger size and by the presence of an external film, which has often disappeared as a result of fossilization. The presence of this film brings Membranitarnax amandopolitanum closer to Membranitarnax ovulum, but in the latter the dimensions are double and the shell has an opening at one end which does not exist in M. amandopolitanum.