Fossiliferous limestone (Fredericksburg Group, Lower Cretacous; Killeen, Texas, USA) 1 : 無料・フリー素材/写真
Fossiliferous limestone (Fredericksburg Group, Lower Cretacous; Killeen, Texas, USA) 1 / 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 | Fossiliferous limestone from the Cretaceous of Texas, USA.The shells in this fossiliferous limestone sample are Gryphaea oysters. Unlike most modern and fossil clams, which have asymmetrically-shaped but equal-sized shells that are mirror images of each other, oyster shells depart significantly from this general rule. Gryphaea oysters had greatly enlarged, coiled, highly convex left valves & greatly reduced, concave right valves. The overall shape of gryphaeids was a consequence of living on soft, fine-grained substrates. All oysters are filter feeders, and practically all are hard substrate encrusters at some point in their ontogeny. Gryphaea oysters were free-living forms as large adults.Classification: Animalia, Mollusca, Bivalvia, Pteriomorphia, Pterioida, Ostreina, Ostreoidea, GryphaeidaeStratigraphy: Fredericksburg Group, Albian Stage, upper Lower CretacousLocality: unrecorded / undisclosed site at or near the town of Killeen, east-central Texas, USA |
| 撮影日 | 2024-10-18 12:27:59 |
| 撮影者 | James St. John |
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