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dasyclad - green algae

Harry Pristis
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Order Dasycladales (calcareous green algae) [dasyclads]

.......... Family Dasycladaceae (extinct and recent)

. Family Receptaculitaceae (extinct)

...........Tribe Receptaculiteae [receptaculitids]

...........Tribe Cyclocriniteae [cyclocrinitids]

.............. Genus Cyclocrinites

Silurian-Ordovician

Wayne County near Richmond, Indiana

"Fossils of this order [dasyclads] are only rarely recognized by collectors.". . .

"Fossil dasyclads are globose to cylindrical or club shaped in outline. They grew on the sea floor to several centimenters in height.

"Internally, a central, noncalcareous structure, the stem or stipe, was surrounded by worled branches or protuberances (rays). . . . They are generally visible only in cracked or broken specimens.

"The primary branches or rays of some dasyclads are rounded at the tip; some have bristlelike or spinelike appendages; others have cuplike or prismlike tips that may be fused as an outer covering of small polygons.

"In cyclocrinitids, the end of each branch is expanded or branched to form a terminal rhomboidal plate. Each plate is one facet in a fused network of terminal plates of other lateral branches so that the surface of the whole body appears as a reticulate shell of calcareous prisms. . . .

"Cyclocrinites is generally a somewhat flattened sphere that has an indentation there the stem (pedicel) was attached. The main central axis was short; lateral branches were very slender, almost rodlike, and arranged in whorls around the central axis. The distal ends of the branches were swollen, and adjacent swollen branch tips coalesced to form the heads, which were polygonal (generally six-sided) in outline at the surface of the spherical body. These polygonal facets were calcified." . . .

Discussion and more images at:

http://www.thefossil...ae/page__st__80

(This image is best viewed by clicking on the "options" button on the upper right of this page => "view all sizes" => "large".)


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© (image only) Harry Pristis 2012
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