Leiospheres

 

Leiosphere is a common name without taxonomic implications for thin-walled smooth or slightly ornamented spherical microalgae. The botanical affinities of leiospheres are unknown.Simple, thin-walled spheres, like Leiosphaeridia, may develop in a variety of algal taxa. When found as fossil remains, these spheres may appear morphologically undistinguishable, despite they are naturally unrelated.

Many acid resistant spherical microfossils have been recorded in sediments ranging from the early pre-Cambrian to Recent. They are widespread in pre-Cambrian and Paleozoic deposits.

 

The taxonomic classification is hazardous and complex in this group where the only features for classification are wall structure, ornamentation, and opening mechanisms. These features are not sufficient for a classification to modern algal taxa above the rank of species—not even at the rank of class.

The importance assigned to morphological characters for classification at the rank of genus or species appears merely to be a question of personal opinion. For modern algae neither shape or ornamentation, nor apertures are relevant taxonomic characters at the rank of genus.

Leiospheres have generally been considered as resting cysts and their aperture (pylome) has been interpreted as an excystment opening. However, they may also represent vegetative stages of the algal life cycle. There may be no possibility of discriminating between vegetative and resting stages (cysts) in fossil material.

 

 

 

		FORWARD TO Morphology and taxonomy Botanical affinities Diagnostic features in modern algae Morphometry of modern and fossil algae Genus Leiosphaeridia Distribution of Leiosphaeridia

 

 

 

 

References

Lindgren, S., 1981.

Remarks on the taxonomy, botanical affinities, and distribution of leiospheres. (Summary in Russian) Stockholm Contrib. Geol., 38(1): 1—20. Stockholm. ISBN 91-22-00500-5. ISSN 0585-3532. — Buy at the lowest prices among books in Sweden.

Lindgren, S., 1982.

Taxonomic review of Leiosphaeridia from the Mesozoic and Tertiary. Stockholm Contrib. Geol., 38 (2): 21—33. Stockholm. ISBN 91-22-00502-1. ISSN 0585-3532. — Buy at the lowest prices among books in Sweden.

Lindgren, S., 1982.

Algal coenobia and leiospheres from the Upper Riphean of the Turukhansk region, eastern Siberia. Stockholm Contrib. Geol., 38 (3): 35—45. Stockholm. ISBN 91-22-00504-8. ISSN 0585-3532. — Buy at the lowest prices among books in Sweden.

Lindgren, S., 1982.

A new taxon of Leiosphaeridia (algae) from Upper Cretaceous clays, southern Sweden. Stockholm Contrib. Geol., 37 (11): 139—143. Stockholm. ISBN 91-22-00487-4. ISSN 0585-3532.

Lindgren, S., 1984.

A new taxon of Leiosphaeridia (algae) from Upper Cretaceous clays, southern Sweden. Stockholm Contrib. Geol., 39 (5): 139—144. Stockholm. ISBN 91-22-00517-x. ISSN 0585-3532. — Buy at the lowest prices among books in Sweden.

 

 

Web Links

Steiner, M., 1997. Chuaria circularis Walcott 1899 — “megasphaeromorph acritarch” or prokaryotic colony? Acta Universitatis Carolinae, Geologica, 40: 645—665. Prague.

Halosphaera, a small planktonic flagellate and a large planktonic cyst; by Charles J. O’Kelly, Protist Image Database

Introduction to the Micromonadophyceae; from University of California, Berkeley.

Non-Marine Palynomorphs from the Middle Cambrian Bright Angel Shale, Grand Canyon USA. Paul K. Strother, Weston Observatory, Boston College.

Terrestrial Organic Remains from Lower Paleozoic Paralic Sequences. Paleobotany Laboratory at Weston Observatory. In Research Projects.

Palynology at the Hole. Rob Fensome and Andrew MacRae, Canadian Association of Palynologists.