19 Şubat 2013 Salı

Fossil Representative of Kansas

Fossil Representative of Kansas

Crinoids (common name)
Crinoids are marine animals that resemble plants. Crinoids that attach to a surface are commonly called sea lilies, and free-swimming crinoids are called feather stars. Both belong to the class Crinoidea of the phylum Echinodermata. Echinoderms, which include modern sea urchins and starfish, are characterized by their radial symmetry and external skeletons. Several hundred species of crinoids are still alive today, but possibly a thousand more are known only through fossils.
Crinoid fossils are common in Pennsylvanian and Permian rocks in eastern Kansas. Excellent specimens have been found in the Iola limestone in Allen County, in the Lecompton limestone formation in Greenwood County, and at other locations in the eastern part of the state. Although Kansas has not designated an official fossil, crinoids are excellent representatives of the geology of the state.
This crinoid is called a sea lily because of its plant-like appearance. The word crinoid comes from the Greek κρίνος  (krinos), which means "lily."
Prehistoric crinoids were composed of three main body parts: the stem, the calyx (head), and the arms. The flexible stem usually anchored the organism to the bottom of the sea. Most modern crinoids do not have stems and are free-swimming. Most of the crinoid’s body is made of protective calcium carbonate.
Stationary crinoids have five or more feather-like arms, with which they filter food particles into their mouths from the waters flowing past them. While living crinoids are normally less than 3 feet (1 m) in length, the main portion of the body of extinct crinoids may have reached up to 82 feet (25 m) in length.
The earliest known fossil crinoids date from the Ordovician period of the Paleozoic era, making them approximately 445 to 485 million years old. Some paleontologists, however, think that certain crinoids first appeared as early as the Cambrian period, up to 540 million years ago.
Crinoids were extremely abundant in prehistoric seas from the Ordovician period or earlier, and throughout the Paleozoic era until the Permo-Triassic extinction event, when they suffered severe losses. This mass extinction event took place approximately 251 million years ago, wiping out nearly 96 percent of all marine species and 70 percent of all terrestrial vertebrates living at the time. Three subclasses of crinoids went extinct as a result of this event. One subclass, called Articulata, evolved in the Triassic period and is the only subclass with species alive today.
In July 2009, a new species, and possibly also a new genus, of stalked crinoid was discovered in the western Atlantic Ocean. This crinoid belongs to a family previously unknown in that part of the world.
Fossilized fragments of crinoids have been found near the top of Mount Everest. This is considered evidence of the dynamic forces that drive faults.
Fossilized segments of columnal crinoids are often cylindrical with a hole through the center. In the Midwestern United States, these are sometimes colloquially referred to as "Indian beads."

Click to enlarge an image
State Prehistoric Creature
Crinoid Fossils, SmithsonianState Prehistoric Creature
Crinoid Fossils, Smithsonian 
State Prehistoric Creature
Fossilised Crinoid Stems
State Prehistoric Creature
Modern Crinoid

Author: World Trade Press

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