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Crinoid Stem showing inner structure.jpg


Dpaul7

Crinoid Stem Showing Interior Structure

 

SITE LOCATION: Fort Payne Chert Formation, Alabama
TIME PERIOD: Mississippian Period ca 350,000,000 yrs old
Data: A crinoid stem. 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. Crinoids are characterised by a mouth on the top surface that is surrounded by feeding arms. They have a U-shaped gut, and their anus is located next to the mouth. Although the basic echinoderm pattern of fivefold symmetry can be recognised, most crinoids have many more than five arms. Crinoids usually have a stem used to attach themselves to a substrate, but many live attached only as juveniles and become free-swimming as adults. There are only about 600 extant crinoid species, but they were much more abundant and diverse in the past. Some thick limestone beds dating to the mid- to late-Paleozoic are almost entirely made up of disarticulated crinoid fragments.
Kingdom: Animalia
Phylum: Echinodermata
Class: Cridoidea


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Photo Information

  • Taken with Canon Canon PowerShot SX120 IS
  • Focal Length 6 mm
  • Exposure Time 1/60
  • f Aperture f/2.8
  • ISO Speed 80

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