Partially geodized crinoid stem (Fort Payne Formation, Lower Mississippian; Rt. 61 roadcut, north of Burkesville, Kentucky, USA) 13 : 無料・フリー素材/写真
Partially geodized crinoid stem (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 | Crinoid stem in the Mississippian of Kentucky, USA.The Fort Payne Formation of southern Kentucky & Tennessee is a shale and limestone succession of Early Mississippian age. Fossils are common to abundant in many intervals. The unit is dominated by crinoids, which are sessile, benthic, filter-feeding, stalked echinoderms. Crinoids are relatively common in the marine fossil record. They are also alive today, but are generally uncommon in modern oceans. A crinoid is essentially a starfish-on-a-stick. The stick, or stem, is composed of numerous stacked columnals, like small poker chips. Stems and individual columnals are the most commonly encountered crinoid fossils in the field. Intact, fossilized crinoid heads (crowns, calices, cups) are unusual. Why? Upon death, the crinoid body starts disintegrating very rapidly. The soft tissues holding the skeletal pieces together decay and the skeleton falls apart.The crinoid stem shown here has been partially geodized. The originally-columnal shape has been modified and expanded, accompanied by quartz-filled fractures covering the surface. Such "exploded" crinoid geodes are relatively common in the Fort Payne Formation.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° 54’ 08.08” North latitude, 85° 25’ 56.19” West longitude) |
| 撮影日 | 2018-03-14 11:48:21 |
| 撮影者 | James St. John |
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