Evolving By Shrinking: How Dinosaurs Became Birds. Most dinosaurs went extinct 65 million years ago but one dinosaur lineage survived and lives on today – we call these the birds and they rule the skies the way they once ruled land.
An international team, led by scientists from Oxford University and the Royal Ontario Museum, estimated the body mass of 426 dinosaur species based on the thickness of their leg bones. The team found that dinosaurs showed rapid changes in body size shortly after their origins, around 220 million years ago. However, these soon slowed: only the evolutionary line leading to birds continued to change size at this rate, and did so for a further 170 million years, producing new ecological diversity not seen in other dinosaur lineages. The study suggests that shrinking their bodies may have helped this group to continue exploiting new ecological niches throughout their evolution, and to become such a diverse and widespread group of animals today.
CLICK FOR LARGER SIZE. No evidence for directional evolution of body mass in herbivorous theropod dinosaurs. Abstract The correlation between large body size and digestive efficiency has been hypothesized to have driven trends of increasing mass in herbivorous clades by means of directional selection.
Yet, to date, few studies have investigated this relationship from a phylogenetic perspective, and none, to our knowledge, with regard to trophic shifts. Here, we reconstruct body mass in the three major subclades of non-avian theropod dinosaurs whose ecomorphology is correlated with extrinsic evidence of at least facultative herbivory in the fossil record—all of which also achieve relative gigantism (more than 3000 kg). Ordinary least-squares regressions on natural log-transformed mean mass recover significant correlations between increasing mass and geological time. However, tests for directional evolution in body mass find no support for a phylogenetic trend, instead favouring passive models of trait evolution. 1. Figure 1. 2. (a) Mass estimates and trees (b) Trend analyses 3. Table 1. 「雷龍」要回來了嗎？ 長長的脖子、龐大的身軀，在草原中緩慢行走，悠哉地吃著樹葉，是大家對雷龍的印象。
可是「雷龍」（Brontosaurus）這個名稱，早在1903年就不再被科學界所用，因為當時的科學家認為牠與迷惑龍（Apatosaurus）是同一種生物，所以其實「雷龍」並不存在。 BUT！ 科學就是這一個BUT……最近古生物學家針對幾種同屬梁龍科（Diplodocidae）的恐龍骨骼研究，發現雷龍與迷惑龍骨骼之間的差異其實很大，足以區分為兩個不同屬的生物。 Once were dinosaurs. The male and female of the oviraptosaur Avimimus, which may have used its feathered forelimbs for display.
Credit: Peter Schouten: Zhao Chang and Xing Lida IF YOU COULD step back to the late Jurassic, 160 million years ago, and conceal yourself in the prehistoric foliage of Mongolia, you would see something remarkable. Between the tree ferns and cycads, an unusual looking bird would appear. It tidies up a clearing – removing leaves, sticks and other debris. Then, with a dramatic flourish, the pigeon-sized creature stands on tip toes, puffs-up its strikingly coloured plumage, and starts to jerkily dance from side to side, all the while producing clicks and shrill little calls. This is actually a courtship ritual, very much like the kind played out by birds of paradise today in New Guinea. It doesn’t have wings, but lightly feathered forelimbs with sharp little claws; and instead of a beak, it has a full set of pointy teeth.
The Institute for Creation Research. "A good tree cannot bring forth evil fruit, neither can a corrupt tree bring forth good fruit.
" (Matthew 7:18) There's something very wrong with our pterosaurs. Humans, not climate, to blame for Ice Age-era disappearance of large mammals, study concludes. Was it humankind or climate change that caused the extinction of a considerable number of large mammals about the time of the last Ice Age?
Researchers at Aarhus University have carried out the first global analysis of the extinction of the large animals, and the conclusion is clear -- humans are to blame. A new study unequivocally points to humans as the cause of the mass extinction of large animals all over the world during the course of the last 100,000 years. "Our results strongly underline the fact that human expansion throughout the world has meant an enormous loss of large animals," says Postdoctoral Fellow Søren Faurby, Aarhus University. Was it due to climate change? For almost 50 years, scientists have been discussing what led to the mass extinction of large animals (also known as megafauna) during and immediately after the last Ice Age. Dinosaurs. Great Dinosaur Pictures. Dinosaur Extinction Theories. 【每日酷知識】恐龍時代 – 國家地理雜誌-中文網.
我們的地球已經45億歲了。 但就我們所知，在這漫長的地球歲月中，生物存在於地球上的時間，其實只是短短的一剎那。 而恐龍又是生長在什麼樣的時代中呢？ 地質時間 地球已經很老很老了，所以研究史前生物和岩石的科學家——也就是古生物學家和地質學家——有他們自己專用的時序表。 因為每個地質時期都有不一樣的氣候狀態和地質活動，像是火山噴發、生長的動植物類型也不一樣，因此會形成不同類型的岩石和化石。 圖片取自：《那時候魚兒還有腳，鯊魚剛長牙，蟲子到處爬》 恐龍時代的結束 大約在6500萬年前，地球上將近90%的生物都死亡了。 圖片取自：《國家地理》數位雜誌互動版 2014.10月號 延伸閱讀： 《國家地理》數位雜誌互動版 2014.10月號 霸王龍，讓開！ 小心，恐龍出沒中！ 持續追蹤，每日小知識，讓您跟孩子分享這世界，每天發現的美好與奇妙。 【恐龍酷知識】不要學《侏羅紀公園》亂混DNA！ – 國家地理雜誌-中文網. 關於恐龍跟蚊子的DNA….
人類對恐龍實在太著迷了，因此催生了好幾部賣座電影。 不過，冒險電影常常把科幻小說與科學事實混為一談。 不要亂混DNA 最有名的恐龍電影應該就屬《侏羅紀公園》了。 在這系列的電影中，恐龍的DNA是從侏羅紀時期的琥珀（也就是樹脂化石）裡的蚊子身上取出來的。 這是第一部《侏羅紀公園》裡的一幕，人類受到霸王龍的威脅。 這個想法很有創意，不過請記住，DNA是會隨著時間而劣化的，因此，無論保存得多完好，都不太可能歷經數百萬年而無損。 【恐龍酷知識】 恐龍的小知識！(二) – 國家地理雜誌-中文網. 跟恐龍有關的知識 ①.
電影《侏羅紀公園》裡的科學家讓滅絕的恐龍再度復活。 目前這還是無法實現的。 圖片取自：《國家地理EVERYTHING系列》-恐龍 ②.1842年，英文的恐龍（Dinosaur）一詞出現了。