Encrinite (Fort Payne Formation, Lower Mississippian; Rt. 61 roadcut, north of Burkesville, Kentucky, USA) 13 : 無料・フリー素材/写真
Encrinite (Fort Payne Formation, Lower Mississippian; Rt. 61 roadcut, north of Burkesville, Kentucky, USA) 13 / James St. John
| ライセンス | クリエイティブ・コモンズ 表示 2.1 |
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| 説明 | Encrinite from the Mississippian of Kentucky, USA. (5.0 centimeters across at its widest)The Fort Payne Formation of southern Kentucky is richly fossiliferous and is dominated by crinoids. Crinoids ("sea lilies") are sessile, benthic, filter-feeding, marine invertebrates that were abundant in Paleozoic oceans. The group nearly went extinct at the Permian-Triassic mass extinction 251 million years ago. Crinoids are not common in modern oceans - they are usually deep-water forms now, but some shallow-water forms also exist today. A crinoid is essentially a starfish on a stick. The stick, or stem, lifts the organism to a moderately high tier above the seafloor, which is conducive to non-competitive filter feeding. The flower-like "head" of the crinoid consists of numerous cemented calcite plates that surround the digestive system and other soft parts. The arms are feather-like and are the structures that engage in filter-feeding. In the fossil record, crinoid stems are common, whereas crinoid heads are uncommon to rare, because they disaggregate quickly after death. Individual pieces of a crinoid stem are called columnals - they are usually somewhat shaped like poker chips. Each columnal is composed of a single crystal of calcite (CaCO3 - calcium carbonate).The limestone seen above is almost entirely composed of crinoid pieces. Such crinoidal limestones are called "encrinites".Classification: Animalia, Echinodermata, CrinoideaStratigraphy: Fort Payne Formation, Osagean Stage/Series, upper Lower MississippianLocality: Burkesville North Outcrop - Route 61 roadcut at milepost 23, way north of Burkesville, Kentucky, USA. (36° 53’ 48.51” North latitude, 85° 25’ 41.08” West longitude)----------------See info. at:en.wikipedia.org/wiki/Encriniteanden.wikipedia.org/wiki/Crinoid |
| 撮影日 | 2018-03-21 10:52:54 |
| 撮影者 | James St. John |
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