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Archimedes bryzoan in matrix, rev crinoid spine a.JPG


Archimedes bryzoan in matrix, crinoid spine on reverse
Bangor Limestone Formation, North Alabama
TIME PERIOD: Mississippian Period (ca 325,000,000 yrs old)
Archimedes is a genus of bryozoans belonging to the family Fenestellidae. The first use of the term "Archimedes" in relation to this genus was in 1838. This genus of bryozoans is named Archimedes because of its corkscrew shape, in analogy to the Archimedes' screw, a type of water pump which inspired modern ship propellers. These forms are pretty common as fossils but they have been extinct since the Permian. Archimedes is a genus of fenestrate bryozoans with a calcified skeleton of a delicate spiral-shaped mesh that was thickened near the axis into a massive corkscrew-shaped central structure. The most common remains are fragments of the mesh that are detached from the central structure, and these may not be identified other than by association with the "corkscrews", that are fairly common. Specimens in which the mesh remains attached to the central structure are rare. Like other bryozoans, Archimedes forms colonies, and like other fenestrates, the individuals (or zooids) lived on one side of the mesh, and can be recognized for the two rows of equally distanced rimmed pores. Inside the branches, neighbouring individuals were in contact through small canals. Bryozoans are stationary epifaunal suspension feeders. The majority of fossils of this genus are distributed throughout Europe and North America, but they have also been found in sediments of Afghanistan, Canada, Russia, and Australia. Crinoids are marine animals that make up the class Crinoidea of the echinoderms (phylum Echinodermata). The name comes from the Greek word krinon, "a lily", and eidos, "form". They live in both shallow water and in depths as great as 9,000 meters (30,000 ft). Those crinoids which in their adult form are attached to the sea bottom by a stalk are commonly called sea lilies. The unstalked forms are called feather stars or comatulids. The taxa is split:
Kingdom: Animalia/Animalia
Phylum: Bryozoa/Echinodermata
Class: Stenolaemata/Cridoidea
Order: †Fenestrida
Family: †Fenestellidae
Genus: †Archimedes

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Photo Information

  • Taken with Canon Canon PowerShot SX120 IS
  • Focal Length 14.4 mm
  • Exposure Time 1/60
  • f Aperture f/3.5
  • ISO Speed 80

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