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Photo Album (I)

 

(by B. Granier)

This page displays photos of some common calcareous Algae, mostly Dasycladales, found in the Lower Cretaceous carbonate platforms.


Heteroporella ? paucicalcarea CONRAD 1970

- Barremian
- Jura

  Heteroporella ? paucicalcareaHeteroporella ? paucicalcarea

Diagnosis: Thallus cylindrical, umbranched. Primary branches numerous, in regular whorls, not mutually compressed, turgid, perpendicular to the stipe at their proximal narrow ends, often slightly inclined at their tips. These branches are assumed to be sporangial chambers. Irregular occurrence of sterile hairs, located within and/or between the whorls. Calcification is irregular: the stipe is commonly coated with a thin membrane only, but the fertile branches are strongly coated and joined together within a whorl. The branches of two successive whorls are joined together near their mid-points. The distal end of the branches is free. [CONRAD 1970]

 

Falsolikanella danilovae (RADOICIC ex BARATTOLO 1978)

- Barremian
- Jura

  Falsolikanella danilovae

Actinoporella (Pseudoactinoporella) fragilis (CONRAD 1970)

- Barremian
- Jura

  Actinoporella (Pseudoactinoporella) fragilisActinoporella (Pseudoactinoporella) fragilis

Diagnosis: The stipe is cylindrical, neither branched out or segmented. The branches are simple, phloiophorous, strongly tilted upwards, arranged in closely set alternating whorls. They communicate with the stipe by means of a proximal narrowing. The calcareous sheath covers a variable proximal portion of the branches and reaches the stipe. Beyond the sheath the branches are enveloped by a rather thin calcareous membrane which is very fragile since the space separating the branches is no longer calcified. the branches converge again at their tips, where they seeem to be a little less tilted. Most likely the assimilatory cortex which characterized the phloiophorous type was situated beyond that part. Where the branches are numerous they squeeze one another and become polyhedral. The reproductive organs are unknown but I think they were located in the branches (cladospory). Both the calcareous sheath and membrane consist of a simple coat of hyaline calcite. [CONRAD 1970]

Salpingoporella genevensis CONRAD ex CONRAD et alii 1973

- Barremian
- Jura

  Salpingoporella genevensisSalpingoporella genevensis

Diagnosis: Cylindrical thallus, neither branching, nor segmented. Euspondylous, alternating, tighted and regularly spaced whorls of a small number of branches. The branches are perpendicular to the axis of the thallus, phloiophorous and compressed vertically. The branches, or some of them at least, contain spores the imprint of which is visible on the calcareous envelope. Calcification is strong and reaches the stipe. No secondary branches. [BASSOULLET et alii 1978]

Cylindroporella barnesii JOHNSON 1954

- Barremian
- Jura

  Cylindroporella barnesii

Montenegrella tubifera SOKAC et NIKLER in GRANIER et DELOFFRE 1994

- Barremian
- Jura

  Montenegrella tubifera

Actinoporella sp.

- Barremian
- Jura

  Actinoporella sp.

Actinoporella nigra (CONRAD et PEYBERN»S 1978)

- Barremian
- Jura

  Actinoporella nigraActinoporella nigra

Photos by courtesy of A. Arnaud-Vanneau
Diagnosis: Small articuled Actinoporella species with a cylindrical main axis bearing close-set whorls of branches. Branch consisting of a vestibule followed by a vesicular to short club-shaped gametophore, by an open pore on one side of the whorl, and by an "excrescence" on the opposite side. Gametophore perpendicular to the main axis and closed at its distal part. Calcareous sheath consisting of microgranular calcite wall. [GRANIER 1995]