原文網址：http://www.bristol.ac.uk/news/2017/october/fossilised-soft-tissue.html
恐龍血液？新研究力勸學者應謹慎看待據稱為軟組織的化石
他們的發現證實先前在恐龍化石中保有角蛋白的主張可能有誤。
類似地，他們也證實許多公開發表在骨頭化石中發現的恐龍血液，也可能是有機物分解後的產物，而非真正的血液細胞。
研究人員為了模擬化石在地底深處經歷的狀況，他們在實驗室採取兩種方法進行處理，一種為利用微生物來分解動物組織；另一種則是讓動物組織承受高溫高壓作用，此過程稱為「成熟」(maturation)。
這項刊登於期刊《Palaios》的研究由布里斯托大學地球科學院的Evan Saitta領導。
他表示：「根據角蛋白的種類，它們在腐敗和輕度成熟作用下的分解模式會產生一些結構方面的差異，像是成熟時血液角蛋白會捲曲起來而不像毛髮的角蛋白會變成波浪狀。」
「這些實驗結果或許能讓我們準確辨識出在近代考古遺址中殘留的角蛋白，但是當我們將成熟作用的溫壓因子提高以模擬埋藏作用和化石形成的環境條件，角蛋白會分解成帶有惡臭且可溶於水的液體，使得它們能溶在水裡或是從化石滲漏出去。」
另一項實驗中，他們在真空環境的電子顯微鏡下觀察分解過後的火雞皮，發現表面擁有皺褶、坑洞和圓形凸起，跟之前研究提出為恐龍血液細胞的特徵十分相似。
從實驗和化石中結構的大小和形狀分布可以明顯得知這些結構是經由非生物作用形成，而非細胞生成之類的生物作用。
因此，這些恐龍骨頭中聲稱為血液細胞的物質可能是分解後的有機物。它們有很大機率是微生物入侵到骨頭裡的空腔所造成，並不是容易分解的血液細胞保存格外良好的案例。
Evan Saitta補充：「我們證實不同種類角蛋白的分解模式具有引人注目的差異，或許有助於辨識出考古材料中殘存的角蛋白。」
「然而，當我們模擬經過長時間的形成化石過程和埋藏作用，發現角蛋白會完全分解成容易從化石流失的液體，代表它們在研究古生物遺骸時沒有什麼用途，縱使過往有些研究抱持相反的主張。」
Dinosaur blood? New research
urges caution regarding fossilised soft tissue.
Their
findings demonstrate that previous claims showing the preservation of keratin
protein in dinosaur fossils are likely to be false.
Similarly, widely publicised claims of dinosaur blood in fossil
bones were shown to likely represent an artefact of degraded organic matter
rather than actual blood cells.
The researchers undertook experimental treatments that either
used microbes to decay tissues or subjected tissues to intense heat and
pressure – a process known as maturation – in order to mimic the conditions a
fossil experiences deep underground.
Evan Saitta from the University of Bristol's School of
Earth Science, led the research which has been published in the journal Palaios.
He said: "Decay and mild maturation resulted in some
intriguing textural differences in degradation patterns based on the type of
keratin such as curling versus crimping of filaments when matured.
"These results may show promise for identifying relatively
recent archaeological keratin remains but when maturation conditions are
increased to simulate conditions present during burial and fossilisation, the
keratin degrades into a foul-smelling, water-soluble fluid that can dissolve or
leach away from the fossil."
In another experiment the vacuum conditions of an electron
microscope appear to have produced folds, pits and blebs in a sample of
degraded turkey skin, similar to those features previously suggested to
represent dinosaur blood cells.
The range of sizes and shapes of these experimental and fossil structures
is evidence that they form through a non-biological process, as opposed to a
biological process like the formation of cells.
Thus, the purported blood cells in these dinosaur bones are
likely to be degraded organics, most likely from microbes that invaded the
cavities in the bone rather than exceptionally preserved, easily-degradable
blood cells.
Evan Saitta added: "We’ve shown that different keratin
types show intriguing differences in degradation patterns that might help
identify keratinous remains in archaeological material.
"However, when the processes of fossilisation and burial
over deep time are simulated, keratin protein fully degrades into a fluid that
can be lost from fossils, meaning little utility for studying paleontological
remains despite contrary claims."
原始論文：Jakob Vinther
et al. Experimental taphonomy of keratin: A structural analysis of
early taphonomic changes. Palaios, October 2017 DOI: 10.2110/palo.2017.051
引用自：University of Bristol. "Dinosaur blood?
New research urges caution regarding fossilized soft tissue."
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