Schweitzer Mary Higby, Wittmeyer Jennifer L, Horner John R
Department of Marine, Earth and Atmospheric Sciences, North Carolina State University, Raleigh, NC 27695, USA.
Proc Biol Sci. 2007 Jan 22;274(1607):183-97. doi: 10.1098/rspb.2006.3705.
Soft tissues and cell-like microstructures derived from skeletal elements of a well-preserved Tyrannosaurus rex (MOR 1125) were represented by four components in fragments of demineralized cortical and/or medullary bone: flexible and fibrous bone matrix; transparent, hollow and pliable blood vessels; intravascular material, including in some cases, structures morphologically reminiscent of vertebrate red blood cells; and osteocytes with intracellular contents and flexible filipodia. The present study attempts to trace the occurrence of these four components in bone from specimens spanning multiple geological time periods and varied depositional environments. At least three of the four components persist in some skeletal elements of specimens dating to the Campanian. Fibrous bone matrix is more altered over time in morphology and less likely to persist than vessels and/or osteocytes. Vessels vary greatly in preservation, even within the same specimen, with some regions retaining pliability and other regions almost crystalline. Osteocytes also vary, with some retaining long filipodia and transparency, while others present with short and stubby filipodia and deeply pigmented nuclei, or are pigmented throughout with no nucleus visible. Alternative hypotheses are considered to explain the origin/source of observed materials. Finally, a two-part mechanism, involving first cross-linking of molecular components and subsequent mineralization, is proposed to explain the surprising presence of still-soft elements in fossil bone. These results suggest that present models of fossilization processes may be incomplete and that soft tissue elements may be more commonly preserved, even in older specimens, than previously thought. Additionally, in many cases, osteocytes with defined nuclei are preserved, and may represent an important source for informative molecular data.
源自保存完好的霸王龙（MOR 1125）骨骼元素的软组织和类细胞微观结构，在脱矿质皮质骨和/或髓质骨碎片中有四个组成部分：柔韧且呈纤维状的骨基质；透明、中空且柔韧的血管；血管内物质，在某些情况下包括形态上让人联想到脊椎动物红细胞的结构；以及含有细胞内物质和柔韧丝状伪足的骨细胞。本研究试图追踪这四个组成部分在跨越多个地质时期和不同沉积环境的标本骨骼中的出现情况。这四个组成部分中至少有三个在坎帕阶时期标本的某些骨骼元素中得以保留。随着时间推移，纤维状骨基质在形态上变化更大，比血管和/或骨细胞更不容易保留下来。血管的保存情况差异很大，即使在同一标本内也是如此，有些区域保持柔韧性，而其他区域几乎呈结晶状。骨细胞也各不相同，有些保留着长长的丝状伪足且透明，而另一些则呈现短而粗的丝状伪足和深色的细胞核，或者整个都有色素沉着且看不到细胞核。我们考虑了其他假说来解释所观察到的物质的起源/来源。最后，提出了一个分为两部分的机制，首先是分子成分的交联，随后是矿化，以解释化石骨骼中仍然柔软的元素令人惊讶的存在。这些结果表明，目前的石化过程模型可能不完整，而且软组织元素可能比以前认为的更普遍地得以保存，即使在较古老的标本中也是如此。此外，在许多情况下，具有明确细胞核的骨细胞得以保存，并且可能是信息丰富的分子数据的重要来源。
