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Undistilled — Fossil Starfish
Published: 2011-04-14 05:41:30 +0000 UTC; Views: 1542; Favourites: 20; Downloads: 94
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Description
(please click image for full view)Title: Fossil Starfish
Medium: Digital Photography
Photographer: Aaron J. Greenblatt
Camera Type: Panasonic DMC-LZ7 Lumix 7.2 MP
Editing: Edited in PhotoShop 7.0 for color accuracy, size, and to apply copyright and border.
Location: Photograph taken at the 49th Annual Gem and Mineral Show held at the American 1 FED, C.U. Event Center - Jackson County Fairgrounds in Jackson, Michigan on March 18, 2011. Show hosted by the Michigan Gem & Mineral Society of Jackson .
Description: Sitting out in the open on a fossil dealer's table (that was covered in a radiant blue tablecloth), was an interesting slab of limestone rock that contained a number of fossilized starfish. The entire slab was a little more than a foot (12 inches) in length and was selling for $225.
The tag next to this fossil read:
FOSSIL STARFISH
(Brittle star, Ophiuridae? Sp.)
Starfish belong to the Echinodermata group, move with suction cups on their legs, and eat plankton. Because they are soft-bodied, fossils of these are rare. If they have extremely long arms, they are referred to as "brittle stars". These beautiful fossil specimens are Ordovician in age (350 millions years old) and are from the Kataoua Formation, Morocco, in northern Africa.
About Brittle Stars: According to Wikipedia, brittle stars (aka "serpent stars"), or ophiuroids, are echinoderms, loosely related to starfish. They crawl across the seafloor using their flexible arms for locomotion. Brittle stars generally have five long, slender, whip-like arms which may reach up to 60 centimeters (24 inches) in length on the largest specimens. Like all echinoderms, brittle stars possess a skeleton of calcium carbonate in the form of calcite. Brittle stars are generally scavengers or detritivores (eating dead organic matter).
Most brittle stars are rarely encountered in the relatively shallow ocean depths normally visited by humans, but they are quite a diverse group. There are some 1,500 species of brittle stars living today, and they are largely found in deep waters more than 500 meters (1,650 feet) down. However, they are not confined to one type of ocean area - and can be found today in all of the major marine environments, from the poles to the tropics.
Brittle Star vs Starfish: In a brittle star, as opposed to a starfish, the central body disk is sharply marked off from the arms. Also, the madreporite (a round orifice used to filter water into the water vascular system and which acts like a pressure-equalizing valve) is usually located within one of the jaw plates on a brittle star, and not on the upper side of the animal as it is in starfish. Digestion occurs in a brittle star within 10 pouches or in-folds of the stomach, which are essentially cavities open only at one end, but unlike in starfish, these cavities almost never extend into the arms. Brittle stars use their arms for locomotion. They do not, like starfish, depend on tube feet, which are mere sensory tentacles without suction.
What's interesting about brittle stars? Brittle stars have neither a head nor an anus. The brittle star's mouth is rimmed with five jaws, and serves as an anus as well as a mouth. Brittle stars have no eyes, or other specialized sense organs. However, they have several types of sensitive nerve endings in their epidermis (skin), and are able to sense chemicals in the water, touch, and even the presence or absence of light. Their tube feet may also sense light as well as odors and the ends of their arms are especially sensitive. Most brittle stars give birth to live young. Some grayish or bluish brittle stars are strongly luminescent.
Brittle stars can readily regenerate lost arms or arm segments unless all arms are lost. They use this ability to escape predators - similar to lizards deliberately shedding the distal part of their tails to confuse pursuers. Moreover, some of them can even regenerate gut and gonad fragments lost along with the arms.
Information Sources:
[link] (wiki - Brittle Stars)
[link] (wiki - Asteroidea - Star Fish)
[link] (wiki - Echinoderm)
[link] (wiki - Madreporite)
[link] (wiki - Water Vascular System)
Barnes, Robert D. (1982). Invertebrate Zoology. Philadelphia, PA: Holt-Saunders International. pp. 949–961.
Legal: Copyright © Aaron J. Greenblatt. All rights reserved. Commercial use prohibited. This image and personal commentary may not be used for any reason without expressed written consent.
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