Remarkable preservation of brain tissues in an Early Cretaceous iguanodontian dinosaur
Remarkable preservation of brain tissues in an Early Cretaceous iguanodontian dinosaur
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DOI：
10.1144/sp448.3
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发表时间：
2017-01-01
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影响因子：
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通讯作者：
Wacey, David
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作者：
Brasier, Martin D.;Norman, David B.;Wacey, David
近年来，化石记录可以保存不稳定的组织，这一点已被接受。我们在这里报告了一个在南极洲发现的禽龙类恐龙的脑内模的软组织的高度详细的矿化。英国苏塞克斯郡Bexhill Wealden河133 Ma的河流沉积物。脑组织壁的成型以及邻近脑组织被磷酸盐和碳酸盐所取代的矿物质使得直接检查石化的脑组织成为可能。扫描电子显微镜（SEM）成像和计算机断层扫描（CT）显示保留了包裹和支持大脑的坚韧膜（脑膜）。脑膜层的胶原链保存在胶膜中。血管也保存在胶磷矿中，内衬或填充有微晶菱铁矿。这些脑膜保存在后脑区域，与现存的祖龙的结构相似。前脑（大脑）比后脑（小脑和延髓区）更清晰，这与先前描述的禽龙级鸟脚类动物的解剖和隐含行为复杂性是一致的。然而，我们要提醒的是，观察到的可能的皮质层与脑壳壁的接近可能是由于在腐烂和埋葬过程中头骨倒置后，脑组织靠着脑壳的顶部沉降而造成的。
It has become accepted in recent years that the fossil record can preserve labile tissues. We report here the highly detailed mineralization of soft tissues associated with a naturally occurring brain endocast of an iguanodontian dinosaur found in c. 133 Ma fluvial sediments of the Wealden at Bexhill, Sussex, UK. Moulding of the braincase wall and the mineral replacement of the adjacent brain tissues by phosphates and carbonates allowed the direct examination of petrified brain tissues. Scanning electron microscopy (SEM) imaging and computed tomography (CT) scanning revealed preservation of the tough membranes (meninges) that enveloped and supported the brain proper. Collagen strands of the meningeal layers were preserved in collophane. The blood vessels, also preserved in collophane, were either lined by, or infilled with, microcrystalline siderite. The meninges were preserved in the hindbrain region and exhibit structural similarities with those of living archosaurs. Greater definition of the forebrain (cerebrum) than the hindbrain (cerebellar and medullary regions) is consistent with the anatomical and implied behavioural complexity previously described in iguanodontian-grade ornithopods. However, we caution that the observed proximity of probable cortical layers to the braincase walls probably resulted from the settling of brain tissues against the roof of the braincase after inversion of the skull during decay and burial.