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Cephalopod egg fossil
Cephalopod egg fossils are the fossilized remains of eggs laid by cephalopods. The fossil record of cephalopod eggs is scant since their soft, gelatinous eggs decompose quickly and have little chance to fossilize. Eggs laid by ammonoids are the best known and only a few putative examples of these have been discovered. The best preserved of these were discovered in the Jurassic Kimmeridge Clay of England. Currently no belemnoid egg fossils have ever been discovered although this may be because scientists have not properly searched for them rather than an actual absence from the fossil record.
==Taphonomy==
(詳細はscavengers and aerobic bacteria.〔 Fossil evidence supports this general idea since swarms of hatchling ammonitellae fossils are known although there are no associated egg fossils.〔 One of the eggs preserved in the Kimmeridge Clay ammonite egg cluster K1486 bears crystalline phosphate on its surface. Since phosphate is mobile only in organic form this suggests the eggs were already decaying before fossilization. The fact that the ammonite eggs survived decomposition to become fossilized suggests two possibilities. The first is that the eggs were transported from the well-aerated location they were originally laid in to low-oxygen waters near the sea floor. The second possibility is that the eggs were laid in waters whose oxygen abundance varied, possibly by season.〔
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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