Geodized crinoid stem (Mississippian; Heltonville, Indiana, USA) 3 : 無料・フリー素材/写真
Geodized crinoid stem (Mississippian; Heltonville, Indiana, USA) 3 / 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 | Geodized crinoid stem from the Mississippian of Indiana, USA.Crinoid are sessile, benthic, filter-feeding, stalked echinoderms. They are relatively common in the marine fossil record and 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 seen here has been geodized. The originally-columnal shape has been modified and expanded. The pentaradial symmetry is still evident.Classification: Animalia, Echinodermata, CrinoideaStratigraphy: unrecorded / undisclosed Mississippian-aged unitLocality: undisclosed site at or near the town of Heltonville, southern Indiana, USA |
| 撮影日 | 2024-05-04 10:59:18 |
| 撮影者 | James St. John |
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