2016年12月8日 星期四

coelurosaur,Tyrannosaurus rex and Velociraptor

這截首度在琥珀中發現的9900萬年歷史「非鳥恐龍」尾巴化石,脊椎、羽毛等細節清晰可見,且琥珀斷面有血跡反應,參與此研究的台北大學運動健康科學教授曾國維昨指,這顯示恐龍被「封」住時才剛死,這項發現可望為恐龍研究打開一扇新窗口。
.......經鑑定後發現,琥珀形成於9900萬年前屬白堊紀中期,而被琥珀保存下的是一段約6公分長的非鳥恐龍尾巴,推測該恐龍全長約18.5公分,尾巴除包含8段完整的尾椎,其上與活著時一模一樣的羽毛,更突破過去化石研究中,只能看壓成平面或已炭化的恐龍羽毛,為鳥類從恐龍演化而來提供更完整證據。
邢立達強調:「一定要說是最小的非鳥恐龍,而非最小的恐龍,因為所有鳥都是恐龍演化來的。」 
研究者推測小恐龍約麻雀大小,身上布滿羽毛。圖為學者想像圖。翻攝網路

體型似近鳥龍

科學家利用3D重建,這隻被命名為「伊娃」的小恐龍骨骼形態與虛骨龍類恐龍(Coelurosaur)類似,而具羽毛特徵可推測其屬手盜龍類(Maniraptora),其體型大小則與1.6億年前生活在中國華北地區、體長約34公分的手盜龍類─近鳥龍(Anchiornis)相近。相關研究結果近日發表在最新一期《當代生物學》。 
斷層掃描顯示「伊娃」尾巴包含至少八段完整的尾椎,且清楚看到羽毛的生長方向。翻攝網路

緬甸續找琥珀

曾國維指出,據骨骼型態還無法判斷伊娃是否成年,但「琥珀很乾淨,沒有動物死前的掙扎滑動或氣泡痕跡」,顯示其被「封」住時已死去。「但標本沒有明顯腐敗特徵,說明牠可能剛死亡,是一具相對新鮮的遺骸。」邢立達表示,目前團隊還在緬甸繼續尋找琥珀化石,加上先前已購入的琥珀,「未來很可能會有更多發現」。 

【報你知】琥珀

琥珀是松柏科植物流出的樹脂,掩埋在地下千萬年,在壓力和熱力下石化形成,被稱為「樹脂化石」或「松脂化石」。而該樹脂作用是植物分泌用來保護傷口和對付害蟲真菌的,樹脂黏性很高,包裹物品後不透氣也不透水且具透明性,加上本身就有抑菌作用,若流出時將昆蟲或動物包裹其中,便能完整精緻地保存樣本。 


NPR
The young coelurosaur, nicknamed "Eva," is closely related to iconic meat-eaters Tyrannosaurus rex and Velociraptor.


Millions of years ago, a dinosaur about the size of a sparrow had a bad day. It got stuck in resin. Paleontologists recently came across the rare amber…
NPR.ORG





腔腸龍的主要群體

極其鳥類的獸腳龍恐龍

腔腸龍
在Mesa西南博物館,Mesa,AZ的Coelurosaur登上。照片©Geb Bennett。

警告:您正在進入一個不斷變化的分類研究領域。這一組的潛伏期的系統發育由涉及其研究的古生物學家辯論,並且新的分類被建議每年幾次!我們將嘗試保持這個網站更新,但現在,當你謹慎地操縱這個劇情展覽的陰影道路,記住,這個不同的組的關係尚未完全理解。這是一個令人沮喪和令人興奮的研究領域。所以仔細從這裡踏上...,看著陰影!飢餓的野獸潛伏在前面!

當前的聯合王國分類

Compsognathus
其中一個UCMP的Compsognathus的演員,從Solnhofen石灰石

龍舌蘭被定義為包含與鳥類更緊密相關的所有獸腳類的分支,而不是與龍族。肺結石的一些診斷特徵包括細長的臂和良好發展的鉸鏈樣踝(腳踝的可能旋轉減少,這在運動期間是有幫助的)。這些特徵可能會丟失或由後來的龍舌蘭(例如鳥)修改。

所有的連鎖龍都顯示出與鳥的大量形態學相似性,但是不同的連環體缺乏不同的鳥類特徵,因此這使得解決該組的系統發育的問題變得複雜。

這個問題的兩個例子是非常鳥狀的Compsognathus longipes(如右圖所示)和Ornitholestes hermanni,從好的標本已知的小的獸腳類,但是他們的系統發育親和力還沒有很好地解決,因為他們共享一些特徵,可能會密切聯合與一個組,但是然後缺少一些被認為是該組的診斷的功能。在這一點上,它們被認為是雪ae;換句話說,我們知道它們是獸腳類;和可能的coelurosaurs;但我們不知道他們是誰相關或如何適應大蜘蛛系統發育的大圖片。

主要腔腸龍類:

Maniraptora:易威猛,鳥類和其他腔腸龍類
Ornithomimidae:鳥模仿coelurosaurs
暴龍:巨型龍捲龍


http://www.ucmp.berkeley.edu/diapsids/saurischia/coelurosauria.html

The Major Groups of Coelurosaurs

Extremely bird-like theropod dinosaurs

Coelurosaur
Coelurosaur mount at the Mesa Southwest Museum, Mesa, AZ. Photo © Geb Bennett.
Warning: You are entering an area of taxonomic research that is constantly changing. The phylogeny of this group of theropods is debated by paleontologists involved in its study, and new classifications are proposed several times a year! We will attempt to keep this site updated, but for now, as you warily maneuver through the shadowy byways of this theropod exhibit, remember that the relationships of this diverse group are not yet understood fully. It is both a frustrating and exciting area of research. So tread carefully from here on…and watch the shadows! Hungry beasts lurk ahead!

Current coelurosaur classification

Compsognathus
One of the UCMP's casts of Compsognathus, from the Solnhofen limestone
Coelurosauria is defined as the clade containing all theropods more closely related to birds than to carnosaurs. Some diagnostic characteristics of coelurosaurs include elongated arms and well- developed hinge-like ankles (possible rotation of the ankle is reduced, which is helpful during locomotion). These features may be lost or modified by later coelurosaurs (birds, for example).
All coelurosaurs show a great number of morphological similarities with birds, but different coelurosaurs lack different bird-like characteristics, so this complicates the matter of resolving the phylogeny of the group.
Two examples of this problem are the very bird-like Compsognathus longipes (shown at right) and Ornitholestes hermanni, small theropods known from good specimens, but whose phylogenetic affinities have not been well resolved yet, because they share some features that might closely unite them with a group, but then lack some features that are considered diagnostic for that group. At this point they are considered incertae sedis;in other words, we know that they are theropods; and probably coelurosaurs; but we don't know who they are related to or how they fit into the big picture of theropod phylogeny.
Major coelurosaurian groups:
ManiraptoraVelociraptor, birds, and other coelurosaurs
Ornithomimidae: The bird-mimic coelurosaurs
Tyrannosauridae: The giant coelurosaurs
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