古代鳥類初生時能夠自行活動 |
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圖二：在約一億二千五百年前的初生雀鳥化石中發現羽毛，顯示牠出生時能自行活動。來自西班牙Los Hoyas的標本MPCM-LH-26189由兩塊石板組成：(甲)白光下的副模 （乙）結合了正副岩石模的激光誘導螢光（LSF）技術結果。這顯示標本周圍的啡色部分包含了羽毛，它們散落在頸和翼，而在左邊翼有一條特別長的羽毛。（丙）白光下的正模。比例尺是5mm。圖片提供: Kaye et al. 2019 Figure 2. Feathers revealed in a ~125 million-year-old fossil of a bird hatchling shows it came “out of the egg running”. Specimen MPCM-LH-26189 from Los Hoyas, Spain is preserved between two slabs of rock: (a) ‘counter’ slab under normal light (b) Laser-Stimulated Fluorescence (LSF) image combining the results from both rock slabs. This reveals brown patches around the specimen that include clumps of elongate feathers associated with the neck and wings and a single long vaned feather associated with the left wing. (c) Normal light image of the main slab. Scale is 5mm. Image Credit: Kaye et al. 2019 請勿於香港時間2019年3月21日下午5時前發放 西班牙Los Hoyas的早白堊紀化石地層 (約有一億二千五百萬年歷史) 一直以盛產數千計的魚類和爬蟲類化石聞名（圖一）。當中有一件既特殊又非常罕有的化石 -- 一副近乎完整的初生鳥類骸骨。香港大學地球科學系助理教授（研究）文嘉棋博士和美國科學促進會(Foundation for Scientific Advancement）的Thomas G Kaye利用他們研發的激光造影技術，在化石標本中發現以往未知的羽毛，揭開了該隻約3厘米長的初生鳥類的生活習性 （圖二）。 雞和鴨在出生幾小時後就能自行活動，牠們屬於「早熟」（圖三）。鴿和鷹則是「晚熟」，牠們會逗留在巢穴內由父母照顧。我們怎樣才能知道初生鳥類是「一出生就能自行活動」 ，還是需要「赤裸孤弱地留在巢穴中」？答案是透過羽毛！「早熟雀鳥」出生時身上有絨毛，在局部地方更有大羽毛，讓牠們不需在母親幫助下保暖和走動。文博士表示：「先前的研究曾嘗試在Los Hoyas初生鳥化石中尋找羽毛，但一直沒有任何發現，因此牠們的生活習性一直是個謎。」 文嘉棋博士和Thomas Kaye利用嶄新的高強度激光造影技術去研究Los Hoyas的化石。這技術讓化石中微小的化學差異發出不同顏色的螢光，揭示了先前未知的解剖細節。他們早前以此技術研究首件發現的羽毛化石，發現其羽根的化學痕跡，並推論它並不屬於著名早期鳥類始祖鳥，解開了一百五十年來的謎團。這次有關初生鳥類的研究成果，讓科學家知道牠們在出生時已有羽毛（圖二及四），因此是早熟和能夠自行活動，解答了有關牠們生活習性的問題。這些羽毛由碳組成，它們在激光誘導螢光成影（LSF）技術下發出微弱螢光，但由於周圍的岩石發出強光，凸顯了羽毛的輪廓（圖二）。「以前曾有研究嘗試用紫外光和同步輻射光都未能發現到羽毛，顯示激光造影技術在古生物學中是一個獨特又有效的新技術。」是次研究的第一作者Thomas Kaye補充。 這個發現顯示一些早期鳥類和現代鳥類一樣，採取了早熟的生育策略。因此，在恐龍時期，一些反鳥類雀鳥幼兒可能以跟隨父母或自行活動來避開在中生代可能遇到的危機。 是次研究的其中一位作者，西班牙馬德里自治大學的Jesús Marugán-Lobón 表示：「其中一條我們發現的羽毛比較大，及保存了在其他初生鳥類可見的羽毛，有理由顯示這初生雀鳥在出生時已長有幫助飛行的飛羽」（圖二乙及四）。這次和早前透過激光成影技術的發現，不僅讓科學家獲取到埋藏在化石中的重要資訊，更讓我們比以前更加了解史前生物。
研究論文 論文連結 (於3月21日下午5時後開放) : http://www.nature.com/articles/s41598-019-41423-7 傳媒如有查詢，請聯絡港大理學院助理傳訊總監陳詩迪女士 (電話: 3917 5286; 電郵: cindycst@hku.hk) 或 港 大地球科學系助理教授 (研究) 文嘉棋博士 (電郵: mpittman@hku.hk). 影片簡述: https://www.youtube.com/watch?v=sXbckTCNlNs&feature=youtu.be |
Ancient Birds Out of the Egg Running |
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(Under Embargo until 17:00 HK time Mar 21, 2019, Thursday) The ~125 million-year-old Early Cretaceous fossil beds of Los Hoyas, Spain have long been known for producing thousands of petrified fish and reptiles (Fig. 1). However, one special fossil stands unique and is one of the rarest of fossils -- a nearly complete skeleton of a hatchling bird. Using their own laser imaging technology, Dr Michael Pittman from the Department of Earth Sciences at The University of Hong Kong and Thomas G Kaye from the Foundation for Scientific Advancement in the USA determined the lifestyle of this ~3cm long hatchling bird by revealing the previously unknown feathering preserved in the fossil specimen (Fig. 2). Chickens and ducks are up and about within hours of hatching, they are "precocial" (Fig. 3). Pigeons and eagles are "altricial", they stay in the nest and are looked after by their parents. How do you tell if a hatchling came "out of the egg running" or was "naked and helpless in the nest"? Feathers. When precocial birds hatch they have developed down feathers and partly developed large feathers and can keep warm and get around without mum's help. "Previous studies searched for but failed to find any hints of feathers on the Los Hoyas hatchling. This meant that its original lifestyle was a mystery," says Dr Pittman. Michael Pittman and Thomas Kaye brought new technology to the study of Los Hoyas fossils in the form of a high power laser. This made very small chemical differences in the fossils become visible by fluorescing them different colours, revealing previously unseen anatomical details. They recently had tremendous success with the first discovered fossil feather which they disassociated from the famous early bird Archaeopteryx by recovering the chemical signature of its fossil quill, a key part of the feather's identification that had been previously unverified for ~150 years. The new results on the hatchling bird finally answered the question about its lifestyle as it did indeed have feathers at birth (Figs. 2, 4) and was thus precocial and out of the egg running. The feathers were made of carbon which has low fluorescence using Laser-Stimulated Fluorescence (LSF), but the background matrix did glow making the feathers stand out in dramatic dark silhouette (Fig. 2). "Previous attempts using UV lights and synchrotron beams failed to detect the feathers, underscoring that the laser technology stands alone as a new tool in palaeontology" added Tom Kaye, the study's lead author. This discovery via new technology demonstrates that some early birds adopted a precocial breeding strategy just like modern birds. Thus, in the time of the dinosaurs, some enantiornithine bird babies had the means to avoid the dangers of Mesozoic life perhaps by following their parents or moving around themselves. "One of the feathers discovered was of a substantial size and preserves features seen in other hatchlings. It indicates that our hatchling had reasonably well-developed flight feathers at the time of birth", says Jesús Marugán-Lobón, a co-author from the Universidad Autónoma of Madrid, Spain (Figs. 2B, 4). This and other "illuminating" discoveries are adding to our knowledge of ancient life with details surviving in the fossil record that were never thought possible even a couple decades ago. The paper: 'Fully fledged enantiornithine hatchling revealed by Laser-Stimulated Fluorescence supports precocial nesting behavior' by T. Kaye, M. Pittman, J. Marugán-Lobón , H. Martín Abad , J. Sanz & A. Buscalioni in Scientific Reports. Link to journal article (available after 5pm on 21 March): http://www.nature.com/articles/s41598-019-41423-7 For media enquiries, please contact Ms. Cindy Chan, Associate Director of Communications of HKU Faculty of Science (tel: 3917 5286; email: cindycst@hku.hk) or Dr Michael Pittman, Research Assistant Professor of HKU Department of Earth Sciences (email: mpittman@hku.hk). Video summary: https://www.youtube.com/watch?v=sXbckTCNlNs&feature=youtu.be Image download: https://www.scifac.hku.hk/press |