53MM Brittlestar Petraster Starfish Fossil & Edrioasteroids Ordovician Morocco

Description

53MM Brittlestar Petraster Starfish Fossil & Edrioasteroids Ordovician Morocco
53MM Brittlestar Petraster Starfish Fossil & Edrioasteroids Ordovician Morocco
Location: Kataoua Formation, Blekus Morocco
Weight: 1 Pound 2.8 Ounces
Starfish Dimensions: 53MM
Dimension: 4.5 Inches Long, 4 Inches Wide, 1.2 Inches Thick (
Plate)
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Brittlestar Petraster
This intriguing limestone slab was extracted from Middle-Upper Ordovician (about 450 million yrs. old) rocks in the Anti-Atlas part of the Atlas Mountains of Morocco. This slab was once part of an ancient seafloor that was uplifted and Incorporated into mountains about 80 million yrs. ago, long after the seafloor turned into thick layers of rock.
The fossils preserved in this slab include early echinoderms (spiny-skinned marine invertebrate animals) known as eocrinoids and ophiuroids (brittle stars). The brittle stars are clearly recognizable, with their five prehensile arms and the compact central body. They look very similar to living species of brittle stars, most of which live in reefs, and shallows near shore and deeper water environments, and feed on small organisms suspended in the water.
Eocrinoids are more unusual, with long thin taperings stems and clusters of arm-like appendages at the opposite end. These animals are probably the Eocrinoid Ascocystites, a suspension feeder that would have extracted food directly from the water column, filtering out micro-organisms with the help of those appendages.
Despite the name, eocrinoids were unrelated to crinoids (seal Lilies) and differ in several morphological features from ancient and modern crinoids. However, like many fossil crinoids, their elongated stem allowed for attachment to hard substrates and the possibility of raising themselves higher off the seafloor.
There appear to be several larger individuals along with a number of much smaller ones. Those smaller animals may be juveniles of the larger form or a different species. Do you notice how the smaller individuals often seem to be in close contact with the brittle stars? We are often led to wonder whether the brittle stars were feeding on the smaller eocrinoids.
Edrioasteroids
are an extinct class of echinoderms. Distantly related to starfish and sea urchins, they have a body laid out in a pentaradial pattern. They also had a water vascular system and a skeleton made of calcite plates. They were filter feeders who lived permanently attached to an object or the seafloor. Some are thought to have had short stems like crinoids but most lived flat on whatever object they had attached to as larva. Edrioasteroids appear in the Cambrian Period about 515 million years ago. The zenith of their diversity during the Late Ordovician Period. By about 275 million years ago, during the Permian Period, Edrioasteroids are extinct.
Edrioasteroids were small organisms from a few millimeters to a couple of centimeters wide. They look like a tiny cushion attached to a substrate. The mouth was in the center of the theca (body) and from it, five ridges radiate out in a pentaradial pattern. These ambulacra channel food along the body to the mouth. There is little fossil evidence of how this was done, but by looking at modern echinoderms, it is likely Edrioasteroids had cilia or tube feet along the ambulacra that moved the food to the mouth. The ambulacra radiate out from the mouth in either straight lines or curves to form a whorl. Usually, they all curve in the same direction but in a few species the curve in different directions.
Please be aware of the nature of fossils:
Being buried under the ground for millions of years under tons of pressure tends to be rough. No fossil comes out of the ground whole and perfect. Most fossils have undergone some restoration, while others are altered by man simply to enhance their presentation in different ways. The workers in Morocco do a very professional job, unearthing and preserving these natural treasures.  These are part of the natural beauty of the fossil and not considered defects.
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