量证据表明，鸟类是恐龙theropod ，而且鸟类进化过程中侏罗系由小型，羽毛手theropods密切相关dromaeosaurids和troodontids （统称为deinonychosaurs ） [小dromaeosaurid microraptor相邻图像显示] 。 确切细节禽流感的起源仍然是辩论的主题，并继续争论是否原始鸟类树登山， leapers ，地面游标，或合并一些生活方式。 是，由于基础deinonychosaurs了小动物（没有多大差别的大小从基底鸟类始祖鸟一样） ，似乎是一个小规模的原始性质deinonychosaur +鸟分支（称为paraves ） 。 们也知道-感谢壮观的早白垩世化石在中国辽宁省-这deinonychosaurs （和其他maniraptorans ）的羽毛像鸟。 句话说，小尺寸和广泛的覆盖了真正的原始羽毛的paravians 。
据我们所知道的恐龙的化石记录，古生物学家普遍认为， 大多数恐龙进化发生在体型比较大的（我的意思在大规模大于几公斤） ，并在动物完全陆地。 尺寸“ （ < 1公斤）和树栖的习惯似乎已经出现相当晚了， 只能在maniraptorans 。 不是说，顺便说一下， 所有 maniraptorans了树栖;只是它的地方在这个分支的树栖习惯演变。
这里，我们看到一个相当不同的建议：断然非标准，非主流鸟类来先（或的bcf ）假说提出的乔治olshevsky 。 确或错误的bcf从来没有讨论的技术文献（至少我已提到的它在史学文章（奈什2000年， b ）段） ，和所有的乔治的文章，它已经在'灰色'或通俗文学（ olshevsky 1991年， 1994年， 2001年，二） 。 谢，主要是，他的活动对恐龙的邮寄名单 （一热门讨论列表恐龙爱好者和研究人员） ，乔治的bcf假说曾是众所周知的，而且许多讨论，并可能认真考虑至少有几个专家[图显示一些的'恐龙，鸟类组成的的bcf假说（阅读） ，与始祖鸟在最右方。 图是©路伊斯和最初出现在olshevsky （ 1994 ） ]
当指出的开始，这个名字'鸟类来先' ，而实际上是误导，因为假设并不建议鸟类的早期演化意义比其它恐龙或其他archosaurs ：相反，它假定小，似鸟，树栖archosaurs的直接祖先， 所有 archosaurs说，后来的（适当的鸟类包括） 。 治是认识到这一事实，显然考虑了相当开玩笑替代简称goodd ，这意味着乔治olshevsky恐龙的后裔。 是当然，意味着对面还开玩笑badd （鸟类是恐龙的后裔） ：这个词乔治使用的'常规'或'主流'鉴于禽流感的起源中所列的前两段以上。 ' badd '是坏的，根据的bcf ，因为它想象体积小，羽毛和树栖习性所有演变很晚archosaur演变，并完全在手theropod恐龙[图显示更多的'恐龙，鸟类的组成的的bcf假说。 些都是早期形式，想象之间将首次archosaur和第一theropod的系统位置。 图是©路伊斯和最初出现在olshevsky （ 1994 ） ] 。
这三个'问题'的标准理论
什么有这样的bcf问题这一普遍接受的概念？ olshevsky分三个具体问题：时间问题' ，在'大小问题' ，和'右翼问题' （ olshevsky 1994年， 2001年） 。 时间问题'是指这样一个事实，即基底鸟类（具体地说， archaeopterygids ）以上者其他paravians 。 鸟maniraptorans （ deinonychosaurs等）都小于基底鸟类， 不超过他们，他们应该如果鸟类从deinonychosaur类的祖先。 石记录表明， olshevsky认为，该大，飞maniraptorans （ dromaeosaurids等）更有可能得到的后裔小，飞行，似鸟的形式，而不是倒过来。 果您已经按照恐龙文学你就会知道，这种想法并不是由olshevsky ：格雷格保罗首次提出在1980年代的dromaeosaurids和其他鸟类一样coelurosaurs可能是其次飞后裔archaeopterygid样的祖先（保罗1984年， 1988a ，乙， 2002年） 。
二个问题提出olshevsky -的'大小问题' -声称，显然小型原始鸟类所需的标准理论的禽流感问题的根源是因为动物往往成为大在其演变，而不是更小（臭名昭著的应对法则） 。 标准的理论，没有明显的解释的theropod小型恐龙向鸟类祖先的存在（ olshevsky 1994年， 2001年） 。 得这一比赛的bcf （假定） ，认为鸟类的祖先是小都（将所有的方式回到archosaurian共同的祖先） ，而且大archosaurs （全部）演变（上许多不同的场合）由这些小祖先。 言之，兼容的bcf寇柏的规则[ dromaeosaurid deinonychus在此处显示，来自维基百科] 。
后，点的bcf的'翼问题。 准理论要求禽流机翼逐渐从最初用于肢体捕食： olshevsky （ 2001年）认为，没有令人信服的模型'解释'这一过渡提出了（他指出，各种不同的假说提出了：这翅膀演变exaptations从羽毛最初用作武器昆虫陷阱，为着色鸡蛋，提供推力，协助操纵运行时，依此类推） 。 bcf因此，遵循同样的逻辑适用于那些鸟类学家谁赞成一个非鸟类恐龙起源：即翅膀'不能'形成的陆地方面，但必须不是产生在树栖设置，使用的动物，它们的前肢减缓或控制他们的行动在跳跃，跳伞，或滑翔。
恐龙系统发育零点的bcf
了提供一个解决办法，考虑到这些'三个问题'的bcf种相结合的'树唐氏模型禽流起源赞成一些鸟类学家（和大多数古生物学家在后海尔曼，预奥斯特罗姆时代* ）与中学飞假说提出的格雷格保罗。 bcf建议恐龙和其他archosaurs开始其历史上的小型，四脚树登山，已经kitted了刺'原始羽毛' ，而且'中央血统'小，树爬形式连接这些二叠系与三叠系形式适当的鸟类进化以后。 有关键的创新，导致了现代禽流条件-骨骼肌pneumaticity ， endothermy ，羽毛，翅膀，减少和丧失的第4和第5手指，脚趾减少横向和修改外翻，减少和丧失的牙齿，尾巴刚等等-发展在这单一完整的宗谱，假设这些成员所提到的olshevsky为'恐龙鸟' 。 龙，鸟类也许类似于许多小，乔木theropods -的arbrosaurs -发明的杜格尔dixon的虚构工作新恐龙 （少数arbrosaurs所示） 。 于传统的理论提供了解释，没有明显的增量出现的'禽流感'字theropods和其他archosaurs ，他们的bcf假定所有演变成逻辑改进树栖，滑翔恐龙，鸟类的生活方式。
*如果你曾经阅读什么鸟的历史起源的理论，你会知道，鸟类最初与其他恐龙早在1800年代末期，最著名的托马斯赫胥黎。 种看法仍然相当流行，直到20世纪20年代时，总理海尔曼的书的鸟类起源以英文出版。 尔曼说，鸟类也不可能是恐龙的后代（主要是因为恐龙缺乏clavicles ，或使他认为） ，因此，他赞成，鸟类起源于所谓的' pseudosuchians ' ：原始archosaurs中也认为祖先化石和鳄鱼。 成为了主流意见，直到20世纪70年代，当新的面貌在解剖证据（加上新的数据手theropods ）领导约翰奥斯特罗姆成功复活恐龙的假设。 好的和最全面审查是鸟类起源的理论提供的witmer （ 1991年） 。
olshevsky已多次指出，他的模型可以完全符合任何特定的'标准' archosaur系统发育。 自己，赞成系统发育的archosaurs绝对是非标准，因此，有效地无关，但它是值得商榷，因为它在这里已经没有多少讨论的其他地方（我在这里我的意见的基础上的细节在olshevsky （ 1991年， 1994年） ，但我知道他的一些看法亲讨论，因为这些作品已经改变） 。 olshevsky的看法非恐龙archosaurs不是真的那么奇怪：他想象crurotarsans形成分支的分歧，从年初的翼龙恐龙分支，以及各种各样的关系，他的提议phytosaurs ， rauisuchians ， aetosaurs ，鳄鱼是如此上是没有什么不同，从标准的系统发育（ olshevsky 1991年， 1994年） 。 而，在最有争议的提议是，奇怪的小三叠纪爬行动物megalancosaurus和longisquama [显示]的恐龙，以及部分大集团（称为theropodomorpha ） ，其中还包括marasuchus ， lagerpeton ， herrerasaurids和theropods （ olshevsky 1991年， 1994年） 。 saurischia不是单系在olshevsky的计划，并sauropodomorphs和ornithischians团结在phytodinosauria （协会最初提出的巴克，以及后来提出的几个工人，但在其他方面不再坚持任何人） 。 sauropodomorpha ，蜥脚类恐龙是被视为最基部的分支，而相比之下，其他分类，他们拥有大量第五脚趾（ olshevsky 2001年） 。
住，在的bcf ，所有的群体大，地面archosaurs分开演变树栖恐龙鸟：在crurotarsans三叠系，在单独的一波又一波的大theropods ，在sauropodomorphs ，并在单独ornithischian分支，我们看到连续的和独立的archosaurian辐射，所有这些下来的树木，并再次向地面生活。
以你有它。 将是错误的成绩在这里：你如何看待批判某种？ 会到明年。
于以前的文章非标准进化假说见...
- 再见从干haematotherm ，再见我的
- 水产原人民和
理论假说的初步二足行走 - amphisbaenians和哺乳动物的起源
以前的文章有关的早期鸟类和禽流感的起源见...
- 羽毛和长丝非禽流恐龙，第一部分
- 羽毛和长丝的恐龙，第二部分
- 龙和斯考滕的长毛的恐龙 ，审查
- 春节动物园图片的一天＃ 24 （关于archaeopterygids ）
- 惊人新的中生代鸟类... 嗯，新的杂交
- 一个快速的历史树爬恐龙
- epidexipteryx ：奇怪的小捷羽毛手
- 在一个月前的恐龙（和翼龙） ： 1 ， therizinosauroid模糊
- 在一个月前的恐龙（和翼龙） ： 2 alvarezsaurids和avialians
- -
什， 4 2000 。 theropod恐龙在树上：历史回顾树栖习性之间nonavian theropods 。 始祖鸟 18 ， 35-41 。
- 。 2000年。 130多年的树爬恐龙： 始祖鸟 ， arbrosaurs和禽流感的起源飞行。 该季刊恐龙学会 4 （ 1 ） ， 20-23 。
olshevsky湾1991年。 修订parainfraclass archosauria应对， 1869年，不包括高级crocodylia 。 版物的要求研究，圣地亚哥。
- 。 1994年。 儿呢？ 论要符合事实。 奥姆尼 16 （ 9 ） ， 34-86 。
- 。 2001年。 儿先：对禽流感的情况起源和早期演化， 1 。 迪诺出版社 4 ， 109-117 。
- 。 2001年。 龙2001年。 3栏： isanosaurus 。 迪诺出版社 4 ， 92-95 。
- 。 2001年。 儿先：对禽流感的情况起源和早期演化。 迪诺出版社 5 ， 106-112 。
罗，人1984年。 archosaurs ：一个进化的研究。 贝尔特•莱夫， w.-e. ＆韦斯特，楼（编辑） 第三次研讨会上中生代陆地生态系统，短文 。 attempto出版社（蒂宾根大学） ，页。 175-180 。
- 。 1988a 。 型食肉恐龙的中期中生代：对角theropods的莫里森和伟大oolite - ornitholestes和proceratosaurus -和镰刀爪theropods的cloverly ， djadokhta和judithriver - deinonychus ， velociraptor和saurornitholestes 。 hunteria 2 （ 4 ） ， 1月9日。
- 。 1988b 。 捕食恐龙的世界 。 蒙与舒斯特，纽约。
- 。 2002年。 恐龙空气：进化与损失的飞行恐龙和鸟类 。 尔的摩：约翰霍普金斯大学出版社，巴尔的摩。
witmer ，爱立信1991年。 流感起源的观点。 舒尔茨， h.-p. ＆ trueb ，研究（编辑） 的起源高级组tetrapods ：争议与共识 。 奈尔大学出版社（伊萨卡，伦敦） ，页。 427-466 。
2010-3-11 0:12:02
论
“ 1个分类：投机动物学” ... ，是因为迪克森参考，或者... ？ β - ）
想提及的是， badd球员，至少在dml ，已采取该标签并运行它，不久自称不好（鸟类是恐龙！ ） 。 有整齐的副作用拟合波段。
布者：大卫诺维奇| 2009年6月8日上午06时37分
好！
果olshevsky称他的假说saacf ！ （小乔木archosauromorphs先！ ） ，可能没有能够找到这么奇怪... 有趣...
是，一旦您添加了白话的“鸟”在您的爬虫类动物系统发育，然后... 云填补与黑暗的天空，雨来了，地球颤抖：这是进化末日！
是制约我国大规模的系统发育dinosauromorphs以测试的bcf ...
布者：安德烈祈| 2009年6月8日上午07时19分
么，它仍然高度unparsimonious 。 规模的问题甚至不存在的，时间问题（这是一直不稳，因为它承担了奇怪的完整化石记录）已蒸发感谢新发现。
布者：大卫诺维奇| 2009年6月8日上午09时02分
谢你做的一切工作，并把所有的东西在一起。 的联系呢！
贴者： j -狗| 2009年6月8日上午九时 30 分
，一些楼宇的鸟类，第一种假设是定义不清或不检验或不主张根据古典假设。 如， arboreality是十分困难的证明/反驳。 ，有多少航班应发达，有多少把握能力应该失去？
有趣的是历史maniraptorian武器/翅膀。 何翅膀可以移交到抓掠夺性武器？ 何捕食把握这部分失去的权力可以outcompete与全套运动前臂？ 什么deinonychosaurids了stangely有限手臂运动？ 什么赫克velociraptor需要巨大的鹅毛笔，旋钮？
布者：耶日| 2009年6月8日上午09时35分
治已经混合了两个思想统一到的bcf 。 ， imho ，是完全合理的：鸟类飞行进化从树上下来。 外，然而，是不是合理的：有一个中央主干，以ornithodiran演变乔木组成的小动物（说，他决定要求鸟类因某种原因！ ）是永远不会永远化石（除了一些明显的非恐龙） ，但总是导致明显的最终结果：鸟类。
果他离开了这个中心主干企业和重点树木下跌人想借此更严重的...
布者：皮特巴克霍尔兹| 2009年6月8日上午10时11
要注册一个评论高，在这个时候名单。
者来此张贴在“生物浓缩”将受到的印象是，奈什认为是植根于完善的科学，但下面的应该牢记：
这些天古生物涉及统计分析算法，努力工作的家庭树（系统发育） ，大多数古生物学家都没有资格以任何远程相关领域。 们很容易误用或误解这些问题，即使对那些具有专门知识，但大多数的古生物学家的结果只是一个简单的计算机程序按面值，尽管一再被告知，世界各国当局，这是错误的。 （然后，他们拒绝，他们这样做。 ）这使得作为多大意义的治疗报纸占星，奉为金科玉律。 多数人会认为，解释复杂的统计证据，只是一个地质程度是相当无意义，但事实上，古生物学家一直努力下去，这一点，忽视适当的专家，并希望能摆脱它。 多人都吸取了最近的经验，社区，甚至整个行业，才能建立多年来，通过领导的人民没有任何资格，这是最终证明是严重的缺陷。 银行，真理所花的时间也出现会比在医药或工程。 生物是安全的，因为尽管示范错误系统发育实际上是不可能的。
有论据支持的bcf是有史以来点击或考虑到以任何方式等奈什，迫使该进程的参数重新启动从一开始就每次。 （部分由于这个原因，论点与cladists只是一轮永远界，因为如果你认为一些白痴从巨蟒素描。另一个原因是，他们不遵循现代科学的原则。 ） olshevsky不是主角现在，我。 会发现我的详细的意见也没有从这个博客上，这是我的名字。 也可以知道我的捐款博客关于这个问题的最肯定不会缺席，而olshevsky没有说很多年。 的论据是，现在，更详细的比olshevsky的。 个企图辩解无视我而言，我认为我还没有发表任何看法，我承认期刊。 然我从来不相信完整那些有能力阻止我国出版物-直到我有一个早期的剧本我即将出版的“秘密dinobird故事” ，并赋予它一种尝试。 在我更加鄙视的完整的古生物学家-而且还小，但价值收集同行审查排斥胡说，以向世界表明。 （如果有人想知道什么样的科学家，我自己，我有一个硕士学位信息。系统。工程。 ，我已经制订了一个形式的人工到实际工作，我教脑科学学位的水平。 ）不，奈什不是一个例外实际上听谁的论点从的bcf营地。 问他究竟为什么对细节的考虑，他坚持按面值cladograms ，他拒绝回答。 否认，他吞下cladograms整体，但如果你调查他的开幕发言中说： “大量证据表明，鸟类是theropod恐龙” ，你会发现不仅是一种误解的性质，证据，而是盲从依赖cladograms 。 过，他建议他使用非树的证据来证明他的观点-这涉及oviraptors我相信-但我们仍在等待细节，尽管我已经提醒他了。
后，一定要认识到奈什的有偿使用引号，如： ...的'大小问题' ， ...的'翼问题' ， ...这翅膀'不能'形成的陆地方面，等和遁词中...果断非标准，非主流... 。 是如何巧妙地描述一方的问题，尚未解决的争议。 么，如果您使用的不是科学，你要使用的东西。
布者：约翰杰克逊| 2009年6月8日上午10时34分
是多么令人着迷的人没有真正认识到问题，但也的能力，科学哲学的历史科学，要建议他们有一些特殊的了解它，他们的对手却没有这样做。
没有任何的bcf （至少我的形式）是较少测试比任何竞争的理论。 “测试”往往是索赔的树为基础的理论，但这种依赖cladograms测试的东西，他们不知道。 什么建议arboreality本质难以证明比建议相反？ 要指责理论中生代问题被定义不清。 明-即理论-可不好界定，因为它喜欢。
部分伪philosopical辩护古生物学家使用的误解原则借用物理科学，这并不适用于以同样的方式向历史科学反正。
布者：约翰杰克逊| 2009年6月8日上午10时54分
好，周到的职务。 待下进入！
布者：凯文函| 2009年6月8日上午10时58
03 -惊人。 的意思是，你真的知道如何写东西，卷筒的极端分子。 指的是美好的杰克逊。
布者： tygo raxx ，三| 2009年6月8日上午11时26分
爱的约翰杰克逊的bcf假说是一个古生物的假设，而不是一个“信息。系统。工程。 ” 型。
不在乎你的程度是：我想知道的论点您使用againts奈什的声明。
您的批评只是rethorical或根据古生物的证据？
出版的“秘密dinobird故事” ，读此 。
：你知道彼得mihalda ？
布者：安德烈祈| 2009年6月8日上午11点56分
@约翰杰克逊
arboreality是的，当然，可能建立。 而，更难以证明的行为（ arboreality ，飞行）比古生物字符（特别是，如果只有部分骨架保存） 。
布者：耶日| 2009年6月8日下午12点○五
只是想知道有多少这种统计专家和paragon科学完整了解archosaurs 。
能等待，看看发挥了这次讨论。 *获得爆米花*
布者： naraoia | 2009年6月8日下午12点五十分
乎很清楚的bcf理论的目标是成为更具争议令人信服。
论一个时间问题， ceratosauria和sauropodomorpha是假设的后裔“鸟”没有出现在化石记录到侏罗纪？ 猜他的意思ornithodirs ？ 们为什么鸟吗？ 然，多数人虽小，但树上？ 有翼龙似乎符合本条例草案。
了应对法（为什么这样一项法律，如果有这么多明显的例外？ ）没有任何理由选择随机功能，并宣布它的祖先的条件？ 什么不先ceratopsians或蜥脚类恐龙排名第一？ 果您不尊重简约那显然不可能设想了一系列循序渐进的步骤从任何套件的任何其他特点。
翰杰克逊
认为，从人类进化的恐龙！ 明我错了！ 有的理论，包括你的，是接受的伪科学。
布者： aleck周| 2009年6月8日下午1时04分
是在这里！ 在这里！ 在我会看...
布者：迈克尔埃里克森| 2009年6月8日下午1时53分
秀后！ 常，非常有趣。 能等待的批判！
布者：迈克尔埃里克森| 2009年6月8日下午2时08分
想说，这是很容易反驳：当适应攀登缺席，尤其是当功能目前阻碍攀登，我们不是寻找一个树栖动物。 少这是最简约的选择。
看，猪头，你有下降的科学家。 取出版分支图，并显示其中的统计误解的基础上; ，或者关闭。
“我在你放屁大方向”不是一个论点！ 出具体的（因此证伪）的论点，或回家。
hmmmmmmmmm 。
知道吗...
一起案件中的“张贴或闭嘴” 。
“秘密” ？ “故事” ？ 果本来应该是科学的，你为什么要穿着它为文学？
外，如果你不知道啊，工程师，我没有得到地质程度。 有一个生物学学位。 生物学 ，你看。
布者：大卫诺维奇| 2009年6月8日下午2时36分
谢你，大卫。 想知道当有人要指出，以jackson先生说，最palaentologists有接地生物学，古生物学看到如何发生的是一个生命科学，而不是什么地狱，他似乎认为它是。
布者：抗议鱼| 2009年6月8日下午4点40分
你是什么叫“人造心” ，和你这是什么意思的“实际工作” ？
能记住您的人工后呢？
你在哪里，以及为什么会发生这种体制称之为“脑科学” ，而不是“神经病” ？
想问只有以供参考。
布者： owlmirror | 2009年6月8日下午5时14分
已阅读四环素动物园在过去的两年中，它肯定是我的收藏科学网站。 一直以为是到了保罗在他的怀疑， deinonychus是后裔archaeopteryxian鸟类。 猜pproblem是一个定义为鸟类总是阿尔奇+现代鸟类。 个人wouldent铭记dromeosaurs被列入鸟类，也许这将最终stabalize恐龙systamatics 。 恨gauther的建议，以限制从价税等值的冠集团，我仍然记得他ornithosuchia “不寒而栗” 。 人onithosuchus ，它不再具有ordial的名字，因为gauther喜欢redifining完全好名字; ） 。
olshevsky的主要问题是在坚持avecephalians是早期theropods 。 正的avecephalians是一个奇怪的集团tetrapods ，特别是coelurosauravis 。 应该对他们博客一段时间达伦。
苯乙烯。 果您需要更多的东西了续集的4月1日龙的文章，您可以使用我的文章分类和进化龙上http://www.scribd.com/doc/16225318/the-evolution-classification-of -的飞龙
布者： 劳拉塔玛拉汉森 | 2009年6月8日下午6点 05 分
声笑！
布者：大卫诺维奇| 2009年6月8日下午6点27
公平的，有古生物学家谁大多地质背景。 您想要在维也纳古生物研究，你可以选择从生物学或从地质;有些地方，或至少已在地质学是唯一的选择。 然而 ，如果你从一开始，你必须采取一些课程在其他;如果您从地质学如今，你可能规划成为biostratigrapher的石油地质，而不是一个phylogeneticist -一个古生物学家的反对palaeobiologist （如othenio阿贝尔意味着这些条款时，他发明后者） 。
布者：大卫诺维奇| 2009年6月8日下午6时33
翰，你是痛苦的，也许无可非议。 管如此，我们这些在这里做你没有错的，所以最好把你的论点和离开的痛苦了。 （它的主要作用是连接你，文本，以实际crackpots ，我现在不得不选择承担您不是。 ）达伦没有写你的问题在所有。 果他使用吓唬引号，这是他的博客，而且你的工作表现出的问题，他怀疑是真实的。
们非常熟悉的现象回声商会领域，看到他们信封许多粒子物理学，天文学，经济学，心理学，神经生理学，和美国的外交关系，在本或记忆中。 生物也不能幸免于它;波段是一个缓缴此类事件。 过，古生物学家，我知道是比较感兴趣的证据表明，违背了他们的成见比说，目前天文学家。
果你有证据，让我们来看看它。 计证据，很难让大多数人评价。 （见http://www.zedshaw.com/essays/programmer_stats.html的言论在不同的领域;钱回复是： “我一直在研究它多年，但仍没有想我知道任何事情。 “ ） ，这将有助于吸引他人（别人）谁真的了解统计数据，以保证您的结果。
个边注意到，我好奇，希望知道什么样的问题，这种人为的思想可以解决。 许有一个网页，我可以将其设置的问题，看看它如何，以及它如何学习？ （我只是希望，密克罗尼西亚，它欠任何mentifex 。 ）
布者：弥敦道迈尔斯| 2009年6月8日下午6时37分
短回应约翰杰克逊...
-不断投诉，古生物学家作为一个整体并不了解机械/算法分支方法，因此不能，也不应该使用它，完全是无稽之谈。 先，未成年人的一点：遗传分类学是不是独一无二的古生物，它广泛适用于整个生物科学和发明了昆虫学家。 应该阅读文学现存生物体上一段时间。 二，我实在不明白为什么你认为你需要了解的统计算法等等完全是一个良好的用户简约软件。 解释为什么你认为这个必要。 as someone who actually uses paup (also nona, sometimes) and has generated cladograms, i think it's far more important that you sort out character polarity, accurate coding etc. thirdly, you are blissfully naïve if you really, honestly think that biologists/palaeontologists truly don't understand this stuff. maybe you don't know that some cladists actually write their own software, or that some have spent the better part of their careers writing about the data handling and computation involved in parsimony software.
-- another of your complaints – that the parsimony software we so doggedly adhere to will one day tumble like a house of cards and that, ho ho ho, won't we all look oh so silly when that day comes – is also rubbish. it is universally understood that the cladograms generated by paup etc. are hypotheses liable to further testing. are you seriously saying that we shouldn't be proposing hypotheses using whatever means we have available?
-- i do agree with you that bcf is essentially testable, but i do not see how this testing supports it. bcf makes direct claims about ancestral conditions at various points on the cladogram. we can test these claims by looking at the fossil evidence we have, and those fossils falsify the predictions of bcf. you're gonna love my next article, as i discuss this matter in some depth therein.
-- finally, please remember that your perpetually condascending tone is really irritating and insulting. as per last time, i decided not to delete your comments because i think you should be allowed to have your say, but i am under no obligation to do this. as you will happily admit i'm sure, you are an amateur with no relevant qualifications. that doesn't mean that you can't sometimes be right, but it does mean that you have no good reason for your constant holier-than-thou, 'we palaeontologists are all a bunch of idiots' rhetoric. there is already one tet zoo regular who frequently has his angry, archosaur-themed rants deleted without hesitation, don't make it two.
posted by: darren naish | june 8, 2009 7:24 pm
dromaeosauridae: note typical long prehensile tail for gripping branch and "hyperextended" perching claw locked in tension, it leapt and "flyde" (guided glide + fly as controlled fall) down to stomp-tackle and bite little critters on the ground (but also vulture-like on carrion, tearing flesh with conspecifics as crocs & komodos do (which is not "conflict" but cooperation)), then leapt back up the tree like a lemur (or tree kangaroo or hoatzal). the tail flattened for flight and could encircle the tree trunk like a spider monkey, the stiff feathers help to grasp. in areas with few trees, became runner but still climbed, had very good eyesight, crepuscular/nocturnal, warmblooded, favored waterside sites but adaptable. may have eaten some sort of plant matter "fruit" occasionally, eg. gingko. 的猜测。
posted by: ddeden | june 8, 2009 7:39 pm
ddeden: all i will say is that you must stop making such 'guesses'. seriously, there is a ton of evidence that is incompatible with just about everything you suggest.
posted by: daniella perea | june 8, 2009 7:43 pm
computing phylogenetic analysis of character matrix for: aves, maniraptoriformes, dromaeosauridae, troodontidae, coelurosauria, archaeopterygiformes, archosauria
using: procrustean elliptical spline transformation
计
计
计
！
computation complete.
果：
75% probability hypothesized relationship is correct
17% probability aves highly derives from lissamphibia
15% probability anatidae-crocodylidae hybrid exists
02% probability segmentation fault - core dumped
0.01% probability contains creamy nougat filling
warning: may contain nuts
warning error danger does not compute does not compute
extrapolate! extrapolate!
+++divide by cucumber error+++
daisy, daaaiiiisyyyy.... ooooowerp.
。
posted by: hexapodoidingaedongaedae | june 8, 2009 7:51 pm
"dromaeosauridae: note typical long prehensile tail for gripping branch"
haha have you ever taken a look at the caudal vertebrae of a dromaeosaur? i figure snapping bones would make gripping branches quite painful.
posted by: aleck zhou | june 8, 2009 8:29 pm
john jackson wrote:
now which part of bcf do you mean john (or is it stephen? or peter?)?1) bird flight evolved from "the trees-down," not "the ground up."
2) the direct ancestors of birds all the way back to the divergence of the crurotarsi were never greater than about 10 kg.
3) the direct ancestors of birds all the way back to the divergence of the crurotarsi should a) be called "birds" and b) had some sort of teleological inclination toward becoming "birdy."
argument one is perfectly reasonable, testable, and in the mainstream of paleontological thought.
argument two is not directly testable, but the principle of parsimony (or ockham's razor or whatever you want to call it) can be applied, and unfortunately, argument two fails when you look at basal tetanurans. it's perfectly possible that basal spinosauroids, basal megalosauroids, and basal carnosaurs all evolved from very small basal tetanurans, but quite frankly it's way more parsimonious to assume that the "direct line" leading to birds went through a "body mass far greater than 10 kg" stage when tetanurae diverged in the early jurassic.
argument three...... is ridiculous, and was what got most people hung up on the bcf idea on the dml for the last 15+ years. everyone, and i mean everyone would consider the clade { archaeopteryx lithographica + vultur gryphus } to be "birds." that's what birds are both scientifically and in common speach. some people would also consider many non-avian maniraptorans "birds" if they saw them in the flesh. but no one would consider the mrca of the clade { allosaurus fragilis + vultur gryphus } a "bird." even fewer people would consider the mrca of clade { iguanodon bernnesartensis + vultur gryphus } a "bird." and george olskevsky himself would probably hesitate to call the mrca of the clade { pterodactylus antiquus + vultus gryphus } a "bird."
yet that's what george wants us to do. he wants this line of mrcas to be called "birds" in addition to real birds.... because this line of tree-dwelling, under 10 kg, never-fossilized dinosaurs were always going to become birds, despite the fact they left lots and lots and lots of ground-dwelling, way over 10 kg, and commonly fossilized descendants.
posted by: pete buchholz | june 8, 2009 9:07 pm
@ 26 - evidence to the contrary? 具体说明。
@ 28 - prehensile tail does not equate with curliness. i was speaking of function (like emperor penguin tail as prop, also woodpeckers iirc) in arboreal transit/posture). note: feathers (partly) encircled trunk, not vertebrae. http://en.wikipedia.org/wiki/dromaeosauridae
posted by: ddeden | june 8, 2009 9:23 pm
i think ddeden was being sarcastic.
john jackson and i (and a few readers) already had it out on my blog a few weeks ago about this very topic.
posted by: zach miller | june 8, 2009 10:32 pm
one issue that's rather important here: why go up into the trees at all? once angiosperms and fruit evolve, there's plenty of high-nutrient food up there (and predators will follow the herbivores), but prior to that? how nutritious *are* gymnosperm seeds, really? i mean, they're digestible, but enough to warrant the difficulty and risk of climbing into a tree to get them.
i should also point out that arboreality is not always obvious from skeletal remains. sure, there are highly adapted species like gibbons and squirrels, but can anyone look at the skeleton of sceloporus or peromyscus and tell how much time they spend in trees?
and remember - most small animals climb extensively, especially those in forested habitat. when you're small, a rock is a mountain and a fallen tree is a huge obstacle. small animals live in rugged world with many of the same challenges faced by arboreal species (slopes, impinging branches, surfaces difficult to balance on, etc.)
posted by: mokele | june 8, 2009 11:53 pm
insect feeding? i'd imagine that many species of insects would have formed to utilize the trees as habitat and a source of nutrition. if there are very few insect-feeding pterosaurs in the area, it'd be an excellent niche for them.
alternatively if they fed on smaller dinosaurs/mammals, they could have used trees as a vantage point to find prey.
posted by: tor bertin | june 9, 2009 12:57 am
mokele: what would keep small animals -- already adapted, as you say, to climbing over fallen trees -- from climbing up still-standing trees? risk of injury from falling is negligible for small animals. in the modern world, climbing a tree may be risking attack, but when the treetops were less populated with flying predators, it must have been a much safer place to spend time, even when there wasn't much food there.
posted by: nathan myers | june 9, 2009 1:10 am
i think john jackson is an insany like peter mihalda
posted by: carlos | june 9, 2009 3:50 am
@ 31 - speculative, not sarcastic, i'd thought.
@ 32 - why up? ask a baby komodo, they're predators too. gymnosperm seeds are rich in protein and lipids iirc, though maybe it was the insects that were food for small ones.
btw, i just read in the local paper of a salamander with a partial-prehensile tail seen and filmed climbing a tall redwood tree, not unusual, redwoods grow past 350' (110m) tall and are very ancient gymnosperms of the coastal fog belt.
posted by: ddeden | june 9, 2009 4:22 am
carlos: if so, he has an excuse for rudeness -- he can't help it. 么是你的？
ad hominem remarks insult everyone. please do your part to keep tetzoo a pleasant environment for us all.
posted by: nathan myers | june 9, 2009 6:04 am
it does, because "prehensile" means "grasping". to this day, prendre (note the dropped h ) is the french word for "take".
1) it is in fact hyperextended. no need for quotes.
2) perching? then why has it got a cutting edge!?!
3) what do you mean by "locked"?
aerodynamically, gliding and parachuting are opposites . you probably can't really do both at the same time.
neither quetzals nor hoatzins leap... unless you count takeoff, but then, all flying birds count. they don't use leaping as a way of locomotion.
i have, let's say, trouble imagining that skin muscles could be so strong as to allow using feathers as a hand.
什么？
not unusual among arboreal plethodontid salamanders!!! put a salamandrid on a tree, and it'll just fall down.
really, you still have a lot of learning to do before you will be able to form informed opinions. you haven't reached that point yet.
it's fine to speculate. it's just useless to speculate without being able to test one's speculations against reality. in many cases you are evidently unaware that such tests are even possible.
to be fair, this was not an ad hominem argument (of the form "i think you're insane, so everything you say is wrong"). it was a conclusion : "everything you say is wrong in such ways that i think you're insane".
"insult" and " ad hominem argument" are nowhere near synonyms. they're completely orthogonal to each other.
posted by: david marjanović | june 9, 2009 7:09 am
mokele:
i can think of a number of possible reasons (in addition to finding gymnosperm seeds to eat) why a small to medium-sized mesozoic vertebrate would occasionally/regularly climb trees:
-to find food, eg, sap, insects (including, from the cretaceous onwards, termites), other invertebrates, and smaller vertebrates and their eggs & young.
-to escape non-climbing predators.
-to find safe roosting and nesting sites.
-to avoid being swept away by the water in certain habitats, such as mangrove swamps and flood forests (like those in the amazon basin today).
posted by: dartian | june 9, 2009 7:28 am
aren't there humongous termite mounds in the morrison fm? i thought termites go all the way back to the triassic…
posted by: david marjanović | june 9, 2009 8:51 am
@ 38 - prehensile is grasp, not necessarily curly. that some animals grasp by constricting the tail wasn't my point. 1) wasn't sure if it was at its limit. 2) lateral stability, tail provided dorsal-caudal stability, (presuming the cutting edge was at the front of the branch, not on top). 3) to prevent unwanted flexion (during rest), the other digits appear to have a dorsal notch at the point of contact just behind their claws, the branch fit between them and the front claw. i think a harrier hawk during dive is in a controlled fall, that's what i'd meant, not parachuting. "quetzals nor hoatzins leap", fine, afaik no extant animal moves the same way as it did. "using feathers as a hand", not as a complex hand, stiff spine feathers as a clutch-brake against gravity and torsion, very little muscular strength required. waterside, initially (aqua-arboreal), later less so. "really, you.." please stop projecting, preach at your own blog.
posted by: ddeden | june 9, 2009 9:07 am
卫：
iirc, grimaldi & engel, in their evolution of the insects (2005), were of the opinion that those triassic mounds were probably not made by termites, and that the earliest indisputable evidence of termites is from the early cretaceous. (i'm no entomologist, however; hopefully christopher taylor will show up and provide some more authoritative information.)
posted by: dartian | june 9, 2009 9:22 am
i've asked the palaeoentomologists i know about these giant morrison termite mounds (photo of one here ). nobody ever seems to know anything.
posted by: darren naish | june 9, 2009 9:26 am
pedantic correction to my previous post:
i should have written "triassic and jurassic mounds" (there are putative triassic termite mounds too, if memory serves me right).
posted by: dartian | june 9, 2009 9:40 am
ddeden,
come on don't be silly. you meant "long prehensile tail" as on a spider monkey. the term prehensile has never been used for the tails of woodpeckers or penguins, and even if we're making up definitions on the fly, they certainly aren't long or resemble dromaeosaur tails in any way. just man up and admit that you did not know dromaeosaur tail morphology essentially kept them immobile.
posted by: aleck zhou | june 9, 2009 10:41 am
if there were no termites in the morrison formation, what was *fruitafossor* eating?
posted by: johannes | june 9, 2009 10:56 am
thank you darren for your contribution to thinking outside of the box imposed by victorian era orthodoxy! i look forward to more articles.
posted by: lou dattilo | june 9, 2009 11:47 am
i thought cope's rule was an artifact of fossilization's tendency to preserve large forms more frequently than small?
posted by: llewelly | june 9, 2009 2:04 pm
david: i thank you for correction, but i took carlos's remark to mean "i think john jackson is [objectionable] ... and therefore we may reasonably ignore his attempts at discourse and, further, try to drive him away with insults." we extrapolated differently, but neither, i think, wrongly.
posted by: nathan myers | june 9, 2009 3:48 pm
john jackson is a ludicrous idiot.
posted by: michael erickson | june 9, 2009 4:01 pm
make that a ludicrous babbling idiot.
posted by: michael erickson | june 9, 2009 4:03 pm
yes, i know that was mean and should'nt have been said, but sometimes you just gotta call 'em as ya see 'em.
posted by: michael erickson | june 9, 2009 4:09 pm
you know, between some of the jj comments here and the quick & ruben paper in journal of morphology , it makes me wonder if i haven't fallen through a timewarp to the 1990s...
posted by: thomas r. holtz, jr. | june 9, 2009 4:20 pm
tom, you mean the new paper about bird knees? i saw the press release, but i don't see how the paper deals with the dinobird connection at all. i mean, the press release included a lot of high-fives from the band, but the connection between knee-driven walking/running and dinosaurs was not discussed (in the press release). and did none of those people read the recent hutchinson paper discussing the gradual transition from "theropod" to avian postures?
posted by: zach miller | june 9, 2009 4:27 pm
@ 45 - no, not immobile. spider monkey tails do not have spiny pen feathers to grip as dromasaurs did, they have ventral eccrine volar surfaces. functionally, in tree climbing, the tails were both prehensile climbing/posture aids. i read one account of an articulated s shaped dromasaur~ish tail, so i thought there might have been some slight curvature (or swivel?) of the caudal vertebrae around the trunk, still not sure about that. but it was the feathers that held, like penguin and woodpecker, not the frictional skin like an oppossum or atelidae.
posted by: ddeden | june 9, 2009 5:09 pm
i agree with zach: why a hypothetical series of avian autapomorphies would challenge the well established synapomorphy-based relationship between (non-avian) dinosaurs and birds? it's only rethorical nonsense.
not only the very good hutchinson's article: did they read the recent literature on saurischian air-sacs (listed here: http://svpow.wordpress.com/2008/10/04/the-aerosteon-saga-part-1-introduction-and-background/)?
posted by: andrea cau | june 9, 2009 5:21 pm
然是。 woodpecker tails don't do any grasping.
how would that work? the entire ventral edge of the claw was cutting, all the way to the tip.
that's to make (slight) hyperextension of those claws possible.
and holding a branch, with one's body weight, against the dorsal side of two toes, against the extensor tendons, strikes me as... unhealthy and painful.
什么？
:-d :-d :-d :-d :-d :-d :-d :-d :-d :-d
ain't got none. 预测。 ;-)
yes, velociraptor .
far too little to grasp anything.
==================================
洲汇率机制。
as darren writes loud and clear, it's george olshevsky's contribution, and it's dead wrong...
you might like to read the post again...
that could contribute, but even if that's ignored, cope's "rule" is an artefact of doing science without math, and of doing evolutionary biology without a good phylogeny. any time people use a method other than eyeballing to look at a case where the "rule" was claimed to apply, it evaporates. that includes my unpublished msc thesis (which i need to do over with yet more data and with better methods, however).
posted by: david marjanović | june 9, 2009 6:39 pm
marvellous discussion, thank you, everybody.
always kick the " "/ball not the wo/man.
cheers, rewi kemp
posted by: rewi kemp | june 9, 2009 7:18 pm
re "cope's rule": i thought dave hone had a paper out recently (2007 maybe?) supporting the rule. he pointed out, iirc, that tests of the rule often assume that the *smallest* species should get larger for it to count as an example, but that this really doesn't make sense: small niches don't go away. and clearly many groups' average and maximum size increase over time.
i think that the main thing is that cope's rule can't be used unmodified: it should be something like "in the absence of mass extinction events and effective competition in the large size niches, a lineage's average size will tend to increase". this would account for things like sauropods getting smaller between the late jurassic/early cretaceous and the late cretaceous - they were largely marginalized by ornithischian herbivores and so could not attain their full potential.
posted by: william miller | june 9, 2009 10:28 pm
ugh, its like the hydra, whack one, and another grows in its place. anyway, excellent article darren. what i find interesting is the fact of how archie seems to have more and more in common with the deinonychosauroid maniraptorans as we dig deeper into its natural history. i mean the recently discovered "thermopolis specimen" is said to have a hyperextendable sickle claw. if archaeopteryx and its kin became a dead-end lineage, i bet that modern day paleontologists would just chalk them up as strange dromaeosaurs or possibly more basal deinonychosauroids.
as for cope's rule, i've been noticing that several paleontologists have been mentioning this lately (both in a for and against context). news flash, cope's rule doesn't exist, or at least not in the terms of modern paleontology. a lineage is just as likely to increase in size over time as decrease, it just does one or the other based on environmental factors influencing natural selection. dwarf elephants, anyone? or do i need to mention how there are still tiny little hyraxes living alongside elephants and formerly mammoths. or better yet, compare a hummingbird to herrerasaurus. cope's rule indeed.
posted by: metalraptor | june 9, 2009 10:33 pm
flattery, as they say, will get you everywhere... ;-)
i don't have much to go on either beyond grimaldi & engel (2005), who state that isoptera body fossils are not known before the cretaceous. triassic wood borings have been attributed to termites, but grimaldi & engel suggest they may have been made by beetles (wood-boring beetles were definitely around at the time). i don't know if they mention the morrison mounds - first i've heard of them, to be honest - but a quick bout of google-fu tells me that similar structures have also been found in the african clarens formation (also jurassic). no fossils have ever been found in association with them, so it seems they could still be just about anything. one abstract seems to be implying that they may not even be biological in origin.
a big potential problem with a pre-cretaceous origin for termites would be that it's not just making a ghost lineage for the termites. the fossil record for the cockroach crown group (which termites are part of) also doesn't seem to go back any further than the late jurassic at earliest. crown dictyoptera (termites, cockroaches and mantids) don't seem to go back much earlier. stem-dictyoptera (the palaeozoic to jurassic "cockroaches") are quite readily distinguished from crown-dictyoptera because they still have an ovipositor, and wouldn't have produced the distinctive egg-cases of crown dictyoptera. i'm not really buying béthoux & wieland's (2009) recent identification of some carboniferous fossils as stem-mantids, but only because that would be just as much (or maybe even more) of a trip for our understanding of dictyopteran stratigraphy as the identification of protoavis as closer to modern birds than archaeopteryx would have been for avian stratigraphy.
posted by: christopher taylor | june 9, 2009 10:35 pm
it can't be a coincidence that you posted this article just as doubts about the bird/dinosaur link are back in the news. in fact, my reason for this particular visit to your blog (well, last night's visit, actually, but i decided to sleep on it) is that i'd just read http://www.physorg.com/news163760732.html and for the sake of my ongoing education i wanted to read a balanced critique of it. if anyone had written such a thing, i thought, it would be darren naish. are you planning to go there?
posted by: adrian morgan | june 9, 2009 10:58 pm
the problem with cope's rule is there's really no scientific mechanism behind it. rather it's a correlation based on observation.
it is true that we do see an increase in organismal size over very long periods simply because the niche at the very top is always open. at a smaller size, niches are more likely to be occupied. furthermore most extinction events have a stronger impact on larger organisms, freeing up those niches. however when niches are empty, a decrease in size can be just as common as an increase in size (island dwarfism, island giantism for example).
posted by: aleck zhou | june 9, 2009 11:13 pm
michael erickson: it's always been easy to be polite to the powerful and the admirable, but that tells nothing about us. we get our chance to demonstrate grace by showing politeness to the weak, the misunderstood, and the loony.
posted by: nathan myers | june 9, 2009 11:40 pm
@ 57 - the tail feathers brace, the tail muscles grasp, probably using the same muscle movement as when landing on a branch. the two large claws and tail provided a secure triangle base on a branch. the ventral claw cutting edge surface assisted in lateral position but did not have weight on them, the weight was behind them on ventral pads. the smaller claws had ventral and dorsal knuckle pads, parallel to knucklewalking african apes (which have mid-finger tissue padding both ventral and dorsal), protecting tendons etc. that the lower claws could hyperextend strengthens this idea, allowing for different size branch circumference. i doubt it would be any more painful than large male gorilla knucklewalking on dry ground.
waterside, as parallel to african apes, vertical tree climbing, part-time brachiating (loose parallel to arboreal controlled fall-flight), some frugivory, some carnivory, atypical ground locomotion (knucklewalking qpal & bipal in ape, hyperextended claws in dromasaur).
i don't know if english is your native tongue, but i was not projecting, i was asserting that you were projecting, and apparently preaching, on a science blog, rather than at your own pulpit.
the vertebrae may have slightly encircled the stem, but it was the axial and radial spiny pen feathers that provided actual friction, and did so while the tail was generally downwards. obviously, i'm not referring to the largest species, which derived from these smaller arboreal ones.
posted by: ddeden | june 10, 2009 1:41 am
口。 tail feathers: "once he's picked up some speed, he tucks his wings in only to pull out of the death-defying descent at the last minute by abruptly spreading his tail feathers".
posted by: ddeden | june 10, 2009 1:48 am
thanks for the information, chris!
johannes:
other insects, apparently. it should be noted that in their original paper, luo & wible (2005), strictly speaking, do not suggest that fruitafossor was a termite-eater; rather, they say that its teeth were most similar to those of modern armadillos. and most armadillo species don't really feed that extensively on termites (or on ants, for that matter) - their diets are more generally insectivorous, or even omnivorous.
(also, the small size of fruitafossor makes it somewhat unlikely that it fed extensively, never mind exclusively, on colonial insects. most extant mammalian termito- and myrmecophages are relatively large and some even have body armour. this probably has to do with the fact that most colonial insects defend their nests vigorously.)
考：
luo, z.-x. & wible, jr 2005. a late jurassic digging mammal and early mammalian diversification. science 308, 103-107.
posted by: dartian | june 10, 2009 2:24 am
adrian morgan (comment 62) writes...
it is entirely coincidental. i was not aware of the new quick & ruben (2009) paper when i wrote the bcf stuff, nor was my article at all inspired by james & pourtless (2009).
sorry, i'm not planning to cover it, predominantly because i don't find it at all interesting nor worthy of review. in recent years ruben and colleagues have made a career of publishing papers in which they assert that 'birds cannot be dinosaurs because of [whatever, blah blah blah]'. quick & ruben (2009) assert that non-avian theropods were fundamentally different in abdominal morphology from extant birds, and they hypothesise (note: hypothesise) that the sub-horizontal avian femur and its associated musculature might be required to prevent collapse of the lateral abdominal wall: non-avian theropods evidently moved their femora a lot during normal locomotion, and hence, say quick & ruben, could not have had abdominal air sacs. all of this is extremely questionable or just flat-out wrong (sternal movement etc. almost certainly was present in non-avian theropods, the 'mobile thigh inhibits abdominal air sacs' just doesn't make any sense, and the authors ignore evidence for abdominal pneumaticity in non-avian saurischians): if the authors have set out to demonstrate anything, it is that evolution cannot happen.
as for james & pourtless (2009): these authors use cladistics to test the hypothesis that birds are deeply nested within coelurosaurian theropods, and argue that they use an unbiased approach where non-dinosaurian archosaurs and other reptiles are included too (they include longisquama among archosaurs for some reason, and even imply that it's a proto-bird [p. 37]). the paper is full of really weird claims (eg, that theropods can only be diagnosed by their intramandibular joint) and does a lot of stuff that's bound to skew the results: they coded all characters of disputed homology as 'unknown' (p. 14), for example (and, as usual among those disputing the theropod affinities of birds, they ignore evidence showing that the disputes about homology are erroneous anyway). this is wrong because it makes an a priori assumption about homology, and it introduces loads of new question marks in the matrix for character states where we do have data. furthermore, the choice of taxa is weird: it's wrong to analyse theropods and other archosaurs without including at least some non-theropod dinosaurs. finally, the trees they generated are entirely uninformative (they are mostly polytomies) and don't provide support for any hypothesis, so quite how the authors can say that they found weaknesses in the 'birds are theropods' hypothesis is really not apparent. as an impartial test of archosaur phylogeny, this study fails miserably.
- -
姆斯岁， fc ＆ pourtless ，茉莉2009年。 传分类学和鸟类的起源：审查和两个新的分析。 鸟类学专着 66 ， 1-78 。
quick, de & ruben, ja 2009. cardio-pulmonary anatomy in theropod dinosaurs: implications from extant archosaurs. journal of morphology doi: 10.1002/jmor.10752
posted by: darren naish | june 10, 2009 5:52 am
谢您的。
when i read articles on science news sites that strike me as dubious, i often search scienceblogs in the hope of reading some knowledgeable blogger's analysis of why the relevant claim is wrong, unlikely, or (as i'm open to any eventuality) actually plausible. i do the same when i read articles that strike me as interesting but sketchy on details. such searches yield results often enough to be worth trying (although it would be nice to be able to restrict the results to recently-published items only).
posted by: adrian morgan | june 10, 2009 6:32 am
let's put the trash out first.
this is supposed to be a science blog, and the best reply to a comment you disapprove of is to disprove it. if you can't do that, simple jeering is not a last resort, it's not even an option; to do so indicates not only that you don't have an answer but that you don't have the kind of mind to produce a relevant answer. genuine science-capable readers eager to save time will be able to judge the worth of a comment by the name, and will soon recognise the likes of tygo raxx, iii, naraoia, owlmirror, hexapodoidingaedongaedae, carlos, and michael erickson, as literally a waste of space.
posted by: john jackson | june 10, 2009 6:45 am
i'm still awaiting naish's reply to the questions i posed as comments to an earlier blog, so there's no point pretending we have a dialogue, but i will address his points:
and i suppose elliott sober is also an amateur since naish would say he isn'ta qualified palaeontologist. perhaps that's how cladists justify the way they've ignored for decades sober's recommendations not to accept cladograms at face value. a field such as palaeontology is made up of specialist sub-fields, and calling oneself a professional palaeontologist does not entitle you to some kind of privileged unassailable authority on any subject within the area you define, nor does it mean those without whatever the appropriate membership card is, are simply 'amateurs'.
the interpretation of cladograms is at the heart of dinobird palaeontology. whatever tickets one may or may not hold, an adequate level of expertise counts. there is more to cladogenesis than running a program, or even than choosing characters well, and it is simply not characteristic of a professional to accept cladograms at face value. when naish stops doing so, that's when i'll stop criticising him for doing it. while he continues, he will be condemning himself more strongly than anyone else can.
it's because you have to know how far their outputs can be trusted. i'll admit the basic principle of selecting the simplest tree is hardly an algorithm at all, and that it's irrelevant that the attempts to achieve this do become rather involved, but understanding the extent to which the simplest tree can represent evolution is the vital skill. with no reversals or convergences, cladograms would be 100% trustworthy; with too much, they begin to lie. what calculation can you do that warns you when this starts to happen? is it when the number of nodes in the cheapest tree divided by its number of character changes is more than 10% of the number of characters? or does it have to be more than the square root of the number of leaves? if we start to approach some such criterion, does that mean we can make no use of the tree, or can we tentatively hold on to it until it gets twice as bad? does it help if some characters appear to misbehave at random but others seem to work together as two or more competing teams? what does it mean if one of the teams contains more characters than all the others? how do we know when the largest team is not the most honest? how do we even know when characters form a team? does the age of the fossils have any relevance at all, and if so, how can it be used? which of these issues are best addressed theoretically, and which by means of simulations?
if you have experience of simulating evolution, if you have enough experience and understanding of using algorithms, statistics and evolution to be able to write a program that weaves and tests its own theories out of patterns of observation that demonstrably aid its survival, then you'll be able to approach the challenges above with a reasonable chance of success, and your attempts at tasks like reconstructing a tricky phylogeny will be worth considering. if you simply say things like 'this possibility was tested using the following animals and characters, and taxon x was found to fall within taxon y', confusing the hypotheses nature of a cladogram with some ability to act as a test while repeatedly denying it, then your attempts will not be genuinely authoritative.
间吃早餐。
posted by: john jackson | june 10, 2009 6:51 am
i cannot believe that you are still using this 'unquestioned acceptance of cladograms' argument. here is a slightly edited version of the response i provided last time (from here )...
--------------------------
i'm not really interested in your approach to this area given that it involves stuff which is beyond my interest and experience. do i 'support' the 'conventional' phylogeny because it is found to be most parsimonious by computational phylogenetic analyses? well, partly, but not necessarily. forget cladistics and all of the assumptions about data analysis that you have a problem with: i return to the point i've made before - that examination (or comparison, or whatever) of the morphological data (you know, the raw information that our phylogenetic hypotheses are based upon) does not find 'dromaeosaurs are nested within the archaeopteryx + modern bird clade' to be the best explanation for the data. you do a very good job of ignoring this, or of remaining ignorant of it.
posted by: darren naish | june 10, 2009 7:04 am
... using a method that ignored the phylogeny. the pterosaur paper just used a linear regression, for crying out loud.
cladogenesis is divergent evolution. splitting of a lineage. "speciation" under some species concepts.
you pontificate about cladistics, but don't understand its most basic terms? 何... reassuring.
长时间之后。
posted by: david marjanović | june 10, 2009 7:15 am
why do you act as if those questions had never been investigated by cladists?
because you don't read the primary literature, that's why. there are entire journals that you don't seem to know exist. yet you make grand pronouncements about how it's all wrong. argument from ignorance. 耻的是你。
––––––––––––––––––––––
on a trunk, you mean? the way chatterjee imagines dromaeosaurids climbed?
(btw, using the tail as a prop, the way woodpeckers do it and the way chatterjee imagines dromaeosaurids did, is not grasping. i don't understand why you glue yourself to that word.)
fine, but why is the 2nd toe (except for the claw) so short, then? and why does the hyperextension happen between the first and the second phalanx, not between the second and the third (which is the claw)?
is that speculation testable by bones alone? probably not…
why, why, why? why should dromaeosaurids parallel african apes in any way at all? what do they have in common skeleton-wise?
(and how much does "waterside" even apply to african apes?)
it's not my native tongue, but i understood full well what you're saying, and i maintain that it's you who's projecting here. you project your lack of knowledge on the rest of the world.
you speculate and speculate, floating high above any data, building castles in the air. half of what you confabulate is untestable (and therefore useless to science), and the other half is already disproved by data you didn't know or even imagine exists. you are the one who are abusing a science blog to launch one trial balloon after another (not even noticing that half of them are heavier than air).
and then you accuse me of doing all that? 只是滑稽。 :-)
while i was already laughing, i tried to continue the joke by saying you projected having a blog onto me. :-)
so far, you're a source of entertainment. just try to learn more anatomy. there's actually much on it online.
posted by: david marjanović | june 10, 2009 9:34 am
nathan myers - you are absolutely right. 不起。
posted by: michael erickson | june 10, 2009 3:09 pm
john jackson - i must say you are right on that part. my comments were uncalled for, i apologize. no more waste-of-space comments from the likes of me.
posted by: michael erickson | june 10, 2009 3:16 pm
john jackson: as i understand it, the demands on rigor in interpreting cladograms are much relaxed if they are used as a source of hypotheses, or to explore a space of hypotheses, rather than as proof for one. the hypotheses really need other support, anyhow, based on deep, detailed anatomical knowledge. no cladogram, however rigorous, can come close to substituting for that.
sometimes a body of raw facts, such as dna analysis, can trump both a rigorous cladogram and the entire population of experts. then the experts have to adjust, but (mostly) they do.
posted by: nathan myers | june 10, 2009 3:27 pm
%lt;sigh>
cladograms are not used for any of these possible purposes. ideally, you start from a dataset (a matrix: taxa x characters), and then have the computer calculate all possible trees for these taxa (automatic generation of all possible hypotheses)*, calculate the length of each tree (that is, how many assumptions of evolution -- of character-state changes -- it requires), and then pick the shortest one(s) based on the principle of parsimony, also known as occam's/ockham's razor, which is one of the two parts of the scientific method. the other part, outright disproof by evidence incompatible with the hypothesis in question, is not possible in phylogenetics**, because, in principle, anything can evolve convergently. there is no absolutely reliable character.***
so, cladistic analyses ( = phylogenetic analyses) are used to test very large numbers of hypotheses against a given dataset using the principle of parsimony; not for generating, proving, or (strictly speaking) disproving hypotheses.
(proof is impossible in science anyway. sure, you can prove beyond reasonable doubt, but you can't define "reasonable".)
that "against a given dataset" part is important. adding taxa and/or characters or simply correcting mistakes in a dataset often changes which hypothesis is most parsimonious. the "deep, detailed anatomical knowledge" you mention is necessary to make a dataset for cladistic analysis in the first place .
cladistic analysis can be, and is often, done on dna sequence data. even mixed datasets are possible and have been analyzed in published papers.
both empirical and theoretical studies show that more data -- bigger datasets -- is better.
何其他的问题吗？ :-)
------------------
* this is where "ideal" and "real" almost always diverge. the number of unrooted trees grows extremely fast with the number of taxa; an exhaustive search as described here is impossible for more than 11 to 12 taxa because it would take forever. instead, other algorithms are used which do not look at every possible tree but still find all most parsimonious trees... almost always.
** this is a point mr jackson likes to harp on ad nauseam. he's entirely right about it... but then he acts as if he had never heard of parsimony...
*** though sine/line insertions come very, very, very, very close.
posted by: david marjanović | june 10, 2009 6:05 pm
aren't there cases where more data just lend more support to the wrong phylogeny?
posted by: naraoia | june 10, 2009 7:06 pm
yes, there can be - for instance, if you're comparing taxa that have undergone high amounts of convergent evolution, and/or if your dataset includes a lot of correlated characters (if a change in one feature automatically causes a change in another feature, you may be counting as two separate changes something that really should be counted as just one). there are ways of getting around these - increase the number of taxa coded to break up long branches, etc. - but unfortunately not all of these will be available in every case. for instance, if you're working on living taxa, checking the results of multiple data types against each other (eg morphological vs. molecular) can act as a test of any individual data type (if they disagree, you'll want to know what makes them disagree and why). stratigraphy and biogeography may also act as checks - while they're not normally included in data sets for analysis (perhaps more a question of how to code them in a way that the computer can handle the analysis appropriately than any other problem), any researcher who finds a triassic taxon nested well within an otherwise purely tertiary clade, or a taxon from mauritius as the sister to a taxon from tahiti, is going to be at least double-checking his data (the result may not necessarily be wrong , but a closer look never hurts).
recognising correlated characters can be a bit trickier, but it usually comes down to familiarity with the organisms you're working with, plus a bit of common sense.
their invocation of convergence, off-hand, has always been one of my major points of confusion about the band crowd. it has been their favoured "explanation" for the morphological similarities between (non-avian) theropods and birds, but i've never heard a suggestion as to why two such ecologically different groups should be so strongly convergent in the first place.
posted by: christopher taylor | june 10, 2009 8:07 pm
david: thank you for the correction. but, what would you call the output of a cladistic analysis? it's the best (by one criterion) of a universe of hypotheses, but it's still a hypothesis, and one you might not have happened upon otherwise. also, deep knowledge is manifestly not necessary to make a dataset; it's needed to make a useful dataset. deep knowledge you don't have yet (nobody knows everythign) is needed to test the output independently. 有？
posted by: nathan myers | june 10, 2009 8:54 pm
@ 74 - imo birds did not evolve from the 'ground-up' from fast running animals that gradually took to the air. flyers (insects, birds, bats, pterosaurs), brachiators and gliders all derived from arboreal (green plant) waterside ancestors (except flying fish). theropods derived similarly, sauropod types did not. 以... grasping as in tensional attachment, as opposed to a terrestrial sauropod locomoting compressionally, where the tail is not used as frictional anchorage. the large-clawed second toe would be weaker if longer, poorer leverage in hyperextension. the closest extant parallel would be a fore-clawed owl or hawk, perching near and above water to ambush prey. not impossibly it may have fed on ginkos and dropped some, 'accidentally' baiting the area, as chimps do with monkeys. some saber-tooth cats probably had a similar aqua-arboreal ambush niche, but nearer the ground. the larger, later ones became more like savanna lions and t rex, due to selection in prey for improved water conservation. african ape and our ancestors formerly were 20ma part-time wetland foragers that then increased arboreal frugivory/omnivory (and so sharing some patterns with dromasaurs and birds). later, savanna chimps, mountain gorillas and humans diverged from that pattern, and adapted unique terrestrial locomotion (knucklewalking ape, upright human). similarly, dromasaurs retained the odd scythe claw, probably using it similar to a saber cat's canines to slash exposed arteries in ambush attempts, which is why most non-humungous dinos had head and dorsal armor, to prevent back-grasping (= tree grasping) predators from getting a good grip without unwanted ventilation. btw, your use of the word 'projecting' is different than what i'd meant. i meant in the psychological sense. don't be so defensive, i'm merely tying up loose ends, noting the parallel niches through time filled by anatomically different but functionally similar species.
posted by: ddeden | june 11, 2009 1:14 am
ddeden: why "waterside", again?
posted by: nathan myers | june 11, 2009 3:57 am
ddeden,
wow, man, i think you are on to something here! these projecting people know nothing. i agree that small dromaeosaurs climbed waterside gingko trees and occasionally ate waterside nuts. but i think it was their s-shaped necks that did the climbing - the spiny, dextrous tail was obviously used to crack the tough nuts. i know this is true because a frog do the same.
posted by: nemo ramjet | june 11, 2009 6:38 am
。 that happens in two different cases:
1) if you have correlated characters in your dataset. that's the same as having one character that is given more weight than the others for no good reason.
2) if you have characters that have undergone such fast evolution that their phylogenetic signal got overwritten. this leads to long-branch attraction* and long-branch repulsion**. that's a common problem with molecular data, but not unknown for morphological data either.
the solutions to 1) are statistical tests for correlation and "deep, detailed anatomical knowledge". for example, is it even possible to have an antorbital fossa without having an antorbital fenestra first? "deep, detailed anatomical knowledge" might answer that.
the solution to 2) are statistical tests for correlation*** and… yet more data! more taxa, so that long branches get broken up; more and clearly independent characters (for example completely different genes) so you see what other evidence says. it is, after all, not likely that different characters contain the same random false signal. it's also good to look at what signals different subsets of the character set contain; if they point in different directions, that needs to be explained. so, what christopher said.
====================
确的。
of course, that it's a hypothesis is not a bad thing. it's too small to be a theory anyway, and a fact is something different in the first place…
that's unfortunately true.
yes, because it's required to 1) find mistakes in the dataset that was used**** and 2) make an even more useful dataset. :-)
* when a clade with lots of autapomorphies = too fast evolution has lost too many of the character states it once shared with others, it finds itself attracted to the root. when there are several, they are attracted to each other and the root…
** when two clades that are in fact closely related lose too many of their shared character states, they will be found apart, because random similarities to other clades will outweigh the vanished evidence for keeping them together.
*** characters that correlate too much to each other are probably just that, correlated characters, and should be turned into a single character (or how many correlation sets there are). characters that correlate too little to any others probably just contain random noise and no phylogenetic signal. – unfortunately, the only rigorous statistical test for both of these at once is so hard to implement that it has only been applied twice, in robin o'keefe's thesis and in o'keefe & wagner 2001 (a paper in systematic biology). there's no software available for it, you'd have to program it yourself.
**** typos are horribly common in published data matrices, and so are similar mistakes. see here for an example where 35 % of a published matrix was, to varying degrees, wrong; the results changed drastically when we tried to correct that.
=============================
好的。
but what do you base this opinion on?
that's exactly how i mean it.
i've been trying to point out that most of them are neither ends nor loose.
again: half of what you say is untestable and therefore useless except if you want to write a raptor red-like book (which, i hasten to add, would be a worthwhile endeavor in its own right!), and the other half contradicts evidence that you happen not to know.
posted by: david marjanović | june 11, 2009 9:17 am
are facts that can't be represented as matrix entries beginning to be discounted as irrelevant?
the word "hypothesis" seems much wider than "a possible output of cladistic analysis". even within cladistic analysis, it seems common to have an interest in a single inheritance relationship, and to run analyses with varied input -- eg assuming each side of a dispute -- to see how robust that detail is against such uncertainties. the hypothesis of interest, then, isn't a particular output tree, but a conjecture about how output trees will be affected by input details.
my impression is that the poster child for failed cladistic analysis must be the placement of falcons among raptors, flatly contradicted by dna evidence despite perhaps the most thorough character analysis ever conducted. did i misunderstand that result?
posted by: nathan myers | june 11, 2009 4:06 pm
what would these be?
maybe you're thinking of continuous characters, whose values are real numbers rather than integers. there are ways of dealing with these in data matrices; i've done it myself.
on the one hand, i don't know if anything might be wrong with those cladistic analyses of dna sequence data. (molecular analyses of bird phylogeny often produce trees with very poor resolution.)
on the other, the gihugrongous analysis of morphological data by livezey & zusi (2007) is... brace yourself... not gihugrongous enough in terms of taxon sampling. it contains almost no fossils. i can't help thinking that this is why, for example, the loons and the grebes were found as sister-groups.
posted by: david marjanović | june 11, 2009 7:54 pm
i guess that means yes. :-)
if (nearly?) the gihugrongousest analysis ever conducted isn't giwhatsit enough, what does that say about every smaller analysis, eg only involving fossil specimens?
posted by: nathan myers | june 11, 2009 8:23 pm
@ 83 - because that's where the optimal combination of water, thirsty prey focused on water, tall trees (shielded against pterosaurs) with low branches (due to open water) for climbing, co-existed. i'm not saying this was the only place, just a favorable one for a dromasaur type predator (as well a raptor, saber-cat and clouded leopard), i'd think.
@ 84 - not sure about the nugivorous frog, but snake scales and dromasaur pen feathers may have had the same frictional climbing ability, just like 'fishscale' pattern on skis, but the feathers function better on thick fissured tree bark, most likely.
@ 85 - comparative physiology, comparative anatomy, optimal apex niche occupation of flora, distance from available metabolic fluid replenishment of prey/predator, availability of alternative foods (fruit/insect), etc. why are you so defensive against sensible speculation? allergy?
posted by: ddeden | june 12, 2009 3:30 am
really, are there any phylogenetically informative characters that can't be put into a matrix? 想不出一个。 助我。
。 that analysis was meant to tackle a really huge problem, and it did so with an uneven taxon sampling. analyses with more fossils in them are usually supposed to handle much smaller problems (smaller parts of the tree of life), and their taxa are more evenly distributed in time.
======================
ok, "a favorable one" sounds better. but why climbing? why do you think dromaeosaurs climbed?
btw, a drom a saur is this .
sounds good -- what is it? all you've explained so far is that you think dromaeosaur feet and tails did not make climbing impossible (...and i explained that i disagree about the feet).
是什么意思？ 不明白... for example, an ecological niche is not a physical space...
i'm trying to get through to you that most of it is not sensible, and that you have to test it.
posted by: david marjanović | june 12, 2009 6:10 am
@ 90 - "dromaeosaur" rather than dromasaur, thanks. "but why climbing?" better visual and launching vantage point above the ground. "what is it?" hooks, like sloth claws and gibbon fingers, but for upright climbing/perching not hanging/brachiation, to allow fast "spiral staircase" vertical climbing/hopping up gymnosperm radial annual branch nodes, moving upward and forward around the stem to the preferred height of ambush, then waited like owls. again, waterside trees, (unlike dense forest trees), retain their low branches, so are easily climbed this way. they did not have opposable thumbs, so they evolved opposable ankle claws and bracing tail feathers. i guess their wings-arms had curved claws.
posted by: ddeden | june 12, 2009 1:49 pm
sorry, i didn't make myself clear enough. why do you think dromaeosaurs did climb? why don't you agree that they lived on the ground?
then why the cutting edge, and why only one such claw per foot? and why does the rest of the anatomy not allow any serious climbing?
ah. now it gets interesting! thank you, this makes sense (...even though i fear it's still not testable, so if it's wrong, we can't find out that it's wrong).
none of the toes are opposable.
this guess is correct. the finger claws were similar to the toe claws of eagles.
posted by: david marjanović | june 12, 2009 7:26 pm
many facts aren't phylogenetically informative but remain biologically important.
by the way, i don't agree that nothing in biology makes sense except in light of phylogenetics. as i understand from people working on bacteria and archaea, their phylogenetics are a near total muddle as a result of them (the cells, not the people) slurping up and incorporating random environmental genetic scraps for a half-billion years. people studying them just have to keep busy in the phylogenetic dark. 们这样做。
posted by: nathan myers | june 12, 2009 8:20 pm
why climb? 物。 insects, fruit, waterside ambush. they probably nested on the ground or treetrunk hollow. early ones were like saber cats and cloud leopards, later ones became open-ground adapted, like lions and cheetahs, as the prey were selected to minimise water use or got armored.
neandertals used the same climb & ambush method at beaver ponds, assisted by herd drivers and backfloating spear-jabbers. a bowhunting friend on his ladder-stand at waterside got off a bad leg shot, so he leapt down on the deer with his hunting knife and slit its throat. stomp, stun & slash, old method, works until prey evolves armor.
one sickle per foot gave lateral stability (not weight bearing) so the arm-wings could tuck and fold for perch & rest. troodonts were similar but nocturnal, keen ears, may have used mouth more prehensilely.
posted by: ddeden | june 13, 2009 3:49 am
aaah 。 in cases where "unknown" or partial uncertainty (like "states 0 or 1 but not 2") don't work, all you can do is run the analysis twice, once coded one way and once the other, and then compare the results. i've seen that done in some publications.
that happens (and has certainly happened for much longer than a mere half-billion years!), but it's not that bad. for example, there's a nice paper in the latest systematic biology on the root of the tree of life.
i repeat: i'm not asking why anyone would climb. i'm asking why you think that dromaeosaurs actually did climb so often that they could be called scansorial, let alone arboreal.
evidence for or against that idea has to come from the skeleton. you brought up the sickle claw, and i showed why it doesn't count. you brought up the tail, and it's clear that alternative explanations can't be excluded for that either (balance, outright rudder for running, sexual selection...). can you find any other evidence that indicates that dromaeosaurs really did climb?
nice story, but how can you show it really happened?
(in those places where neandertalers and trees co-occurred. which aren't that many.)
then why has no other climber evolved such a claw, and why has it got a cutting edge? and why is it so big?
wouldn't something like a primate/marsupial/drepanosaurid foot work much better for stability in all directions?
posted by: david marjanović | june 13, 2009 7:46 am
hang a sickle and a gaffing hook on a branch, the hook can slide laterally, the sickle cannot, tetrahedral tripodal bipedal lateral stability. today's birds have a secure sleep-proof rear claw/s which does away with the need for a vertebral tail prop and sickle stabilizer in upright orthogonal stance. once the rear grasping claw evolved, long vertebral tails and teeth were lost and birds flew high, which gradually displaced dromeaosaurids and troontids from apex arboreal ambushers, they became large ground runners. long vertebral tails initially braced, not for running balance or rudder (weight), or sexual selection (did not protect hutch unlike peacock), and females probably had the same tail prop.
neandertals hunted waterside via ambush, young skinny males in trailside trees, older fat males in water with long spears, females prodding herd to waterhole. later, more open herd hunting, like lions and wolves.
primate digits didn't evolve for "falling" but for climbing and plucking. the dromaeosaur's advantage was a fast controlled stomp tackle, it wasn't a great climber, just an adequate one.
posted by: ddeden | june 14, 2009 12:10 am
。 why didn't that evolve right away?
not remotely comparable. it took a long time till birds reached that kind of size; no flying birds of such size exist today, for example.
thin and muscle-poor as the weight is, i doubt that's an argument.
irrelevant. traits for which there is sexual selection are usually useless; that's even the point.
what makes you think so?
as far as i can see, they were rather inadequate climbers.
posted by: david marjanović | june 15, 2009 10:27 am
thanks, commenters, for my several prolonged and hearty lol reading the above. but much of it is also beyond my ability to comment.
so here is a photo which i hope will make it all clear..
posted by: graham king | june 20, 2009 12:09 pm