梦は时空を越えて - 岸田教団



度娘，有种继续。

回复 制乙烯170 :这个词的意思是坚硬的支撑，也可以做支点解，我翻译取后者。

ps.约翰·康威你可真会玩，连David Peters都不敢把Sharovipteryx的前肢画成这样。

第三章·翼龙与鸟Cosesaurus：梦消失
接下来出现的，就是一个最为神秘的存在，让无数飞行学说都无法真正成立，甚至混淆了鸟类和翼龙的关系，同时又颠覆了羽毛的奥义。

一个2分钟的短片，讲述了翼龙起源这个最大的谜题。
《翼龙起源与演化：传奇历程》
同样有一本同名书籍。

@Dhallorum
https://getinfo.de/app/details?cluster=tib&term=The+function+of+the+manus+and+forelimb+of+Deinonychus+antirrhopus+and+its+importance+for+the+origin+of+avian+flight&tib=zbwkat&tib=roempp&tib=blcp&tib=dkf&tib=sudoc&tib=tema&tib=ceaba&tib=zbmkm&tib=ntis&tib=rdat&tib=tibkat&tib=citeseerx&tib=blse&tib=k
Alan Gishlick坚定认为羽毛不会妨碍前肢活动，且指出Senter在生物力学模型上的问题所在；会议记录访谈，不知道能不能看到，我这边有时候可以有时候又不行。
恐爪龙的前肢的确存在一个两侧大约45-60度的限位，但这显然不能成为“在单侧前肢握紧时另一侧前肢抓握范围会受到干扰，前肢向下拉直时旋前肌肉组自动解除干涉手掌自动旋后”的证据所在。

人在武汉，文档忘了拷贝，先讲讲最近看的一点东西，权当更新。
Respiratory Evolution Facilitated the Origin of Pterosaur Flight and Aerial Gigantism
关于翼龙呼吸机制的探究。
很久以来，没有多少人将目光寄托在翼龙的呼吸系统上。我们似乎无视了这个重要的特征；有限的一些文献，研究的方式存在着或多或少的问题，或者局限于某一个特殊类群。直到2009年，The Deep Time的作者联合另外两位学者，做了有史以来最全面的翼龙呼吸方式研究。
我们似乎很容易就想到翼龙和鸟类、蝙蝠的相似性。研究也确实从某一个层次肯定了这一观点。鸟类被公认为最简三位一体的呼吸机制不用多说，这是很常见的话题，也已经被提烂。
鸟类的胸腔本身比较有意思，它缺乏远端软骨段。这似乎意味着这样的胸腔缺乏纵向活动性，而翼龙也是如此。在有气囊的爬行类当中，比如鳄鱼，肋骨的背段往往限制了整体的运作。
而翼龙的解决方案是：胸部变为一个巨大的杠杆。


上桑塔纳古魔翼龙，下无齿翼龙和喙嘴龙的胸腔。注意肋骨特征。难道这样的胸腔真的只是一个牢笼，嘛？
连接胸骨的肋骨片断的形状和大小显示，胸腔是可移动的，这与先前的观点相反。肋骨上唯一先前没被承认的凸出物给肺部呼吸肌肉提供重要的杠杆作用。这一系统的优势作用区域集中在腹侧，并且拥有极其强大而高效的运作效率。在每次拍打翅膀时，胸腔连为一个整体。肋骨上端拉动下段和胸骨前后移动，这一举措使得肋间肌的工作效率也提高了。由于后胸骨肋较长的力臂，这个位置会有最大的通气量（看不懂请温习小学科学课本），从而确保翼龙的最优呼吸效果。

这种与鸟类不谋而合的套路，在比鸟类早了近亿年的飞行生物身上出现。令人惊叹。
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0004497

Finding higher resolution data
is always a delight. Here DGS and a reconstruction perhaps reveal more accurate data on a skull of a basal pterosaur than direct observation (Fig. 1). You decide.
Figure 1. Begamodactylus skull using DGS to segregate and reconstruct the elements. Lower images from Kellner 2015.
Figure 1. Begamodactylus skull using DGS to segregate and reconstruct the elements. Lower images from Kellner 2015. Note the difference in the tracing of the jugal and the reconstruction of the jugal by Kellner 2015. Some odd things are happening on close examination. Kellner actually traced both jugals there and the quadratojugal is actually the postorbital process of the jugal. The squamosal process of the postorbital is broken so the divergence has been reduced. The teeth are also different. The occiput was not traced originally. A hyoid is in the braincase, overlooked by Kellner.
Kellner (2015)
commented on several Triassic European pterosaurs. Among them, MPUM 6009 was originally described as a juvenile Eudimorphodon by Wild (1978) and later congeneric with the basal anurognathid, Carniadactylus by Dalla Vecchia (2009). Peters (2007) nested this specimen as the basalmost pterosaur, though this reference was not listed. Kellner (2015) reported “no indication that MPUM 6009 is a juvenile.” confirming the assessment here.
Bergamodactylus wildi
is the new name for MPUM 6009 a Late Triassic (Norian) basal pterosaur from Bergamo, Italy. Unfortunately the tracing of the specimen is very vague (Fig. 1). Both jugals are drawn as one and many bones are not identified. This is remedied by DGS, which not only identifies left and right bones, but enables an accurate reconstruction with all parts fitting as in other articulated pterosaurs. Note the twin anterior dentary extensions. Are those teeth? A keratin extension has been hypothesized for other basal pterosaurs. Part of the maxilla ascending process is broken and flipped but repaired above. The posterior process of the left postorbital is broken like a wishbone. Here (Fig. 1) it is repaired to resemble the right postorbital. The occiput is identified along with several hyoids that were overlooked earlier. Does the coronoid have a tall triangular process? Perhaps, but that could also be an ectopterygoid. We’ll have to see about that.
Figure 2. Updated reconstruction of Bergamodactylus to scale with an outgroup, Cosesaurus.
Figure 2. Updated reconstruction of Bergamodactylus to scale with an outgroup, Cosesaurus. Compared to the cranium and declined quadrates, the face appears to be downturned. This only makes sense in a bipedal configuration, as shown.
References
Dalla Vecchia FM 2009. Anatomy and systematics of the pterosaur Carniadactylus (gen. n.) rosenfeldi (Dalla Vecchia, 1995). Rivista Italiana de Paleontologia e Stratigrafia 115 (2): 159-188.
Kellner AWA 2015. Comments on Triassic pterosaurs with discussion about ontogeny and description of new taxa. Anais da Academia Brasileira de Ciências (2015) 87(2): (Annals of the Brazilian Academy of Sciences) Printed version ISSN 0001-3765 / Online version ISSN 1678-2690.
Nesbitt SJ and Hone DWE 2010. An external mandibular fenestra and other archosauriform character states in basal pterosaurs. Palaeodiversity 3: 225-233.
Peters D 2007. The origin and radiation of the Pterosauria. In D. Hone ed. Flugsaurier. The Wellnhofer pterosaur meeting, 2007, Munich, Germany. p. 27.
Wild R 1978. Die Flugsaurier (Reptilia, Pterosauria) aus der Oberen Trias von Cene bei Bergamo, Italien. Bolletino della Societa Paleontologica Italiana 17(2): 176–256.

呐= =一点都不想更新啊怎么办。
算了，搬运一篇洪大卫的博客。这里只摘录他关于翼龙起源的部分。
Pterosaur.net:: Origins and Relationships
By Dave Hone
http://pterosaur.net/origins.php
Pterosaur origins – where did the come from?
Now comes the tricky part of cladistics. Pterosaurs are really, really strange. As a result of evolving flight, their bones and bodies underwent some enormous transformations. Essentially, much of the information we would look for was lost, so there is little to tie pterosaurs to other groups through shared characters. This means that it is actually quite hard to see how pterosaurs fit in the great tree of life. We do know that they are diapsid reptiles – to special holes in the skull give that away, but after that things get tricky. It really boils down to two possibilities - the dinosauromorphs (that also produced the dinosaurs) or the basal archosauromorphs (that spawned many lineages).
Pterosaurs share some characters in common with each of the two groups, primarily features of the legs with the dinosauromorphs, and a few scattered ones, mostly in the neck, with the archosauromorphs. There is not much to chose between them, and even many pterosaur experts disagree, but right now the weight of evidence falls (just) on the side of the dinosauromorphs.
现在到了棘手的部分。翼龙是真的，真的很奇怪。由于适应飞行的结果，他们的骨头和身体经历了一些巨大的转变。实际上，很多信息我们缺失了，所以我们很难对翼龙进行一个合理的分配。这意味着，实际上很难寻找到一个适合翼龙的、伟大的、美好的爬行动物进化树。我们知道他们是已经灭绝的爬行动物–有着头骨标志性的特殊孔洞（现在在喙头蜥身上还能看到这种头骨的结构），但那之后事情变得棘手。它可以归结为两个可能性———恐龙形类（这也产生了恐龙）或基底的主龙类（这就产生了许多不同的可能性）。
翼龙与两者都有某种程度上的联系，比如恐龙形类的后肢，与鸟颈类主龙的相似处则主要集中在脖子和其他一些零散的成分。在这两者之间没有太多的选择。甚至许多翼龙专家不同意这样的观点，但是现在明显的，我们更倾向于鸟颈类的起源，而恐龙形类的证据比例在这一方面下降了。

续，一篇比较好玩的Evan Robinson博客，关于蛋的：
http://dml.cmnh.org/2004Jul/msg00350.html
From the Pterosaur embryo fossil tread where David Peters suggests viviparity as an explanation for the small young that he sees accompanying various prolacertiforms and pterosaurs. The recent finding of a pterosaur embryo in a hard-shelled, chicken size egg endangers his theory.)
All known archosaurs, as well as turtles, and even the extant lepidosaur Sphenodon have a condition known as embryonic diapause. This means that their eggs suspend development if retained in the uterus, and only resume development after they have been laid. Thus, prolonged retention of the eggs, which could occur for various adaptive reasons, and which is the predecessor to viviparity, will never occur, and therefore viviparity will never develop. For this reason, viviparity in all archosaurs is unlikely.
In squamates, however, the transition from oviparity to viviparity has occurred many times, and incidentally, reversals may never have occurred (the theory being that the egg laying structures cannot be regained). Taking the Gekkonidae family as an example, the extant Gecko gecko, as well as Phelsuma Madigacaraian, lay hard-shelled eggs. Yet many others in the family have soft eggs, and others have developed viviparity.
--- K and T Dykes <ktdykes@arcor.de> wrote:<<The embryonic skeleton, which is exquisitely preserved in its egg, isassociated with eggshell fragments, wing membranes and skin imprints.> > That seems to suggest at least one pterosaur laid eggs, the shells of whichcould fragment; ie. an egg a with hard shell as known from crocs, non-birdy dinos and birdies. That sounds like a very archosaurian kind of thing to do. .
T. Michael Keesey wrote:
Or at least archosauromorphan. The major hypotheses of pterosaur origins place
them either in the immediate outgroup to _Dinosauromorpha_ ("The Ornithodiran Hypothesis") or outside _Archosauria_ sensu stricto (the most exclusive clade containing crocodylians and
avians), but still within _Archosauromorpha_ (the most inclusive clade containing archosaurs but
not lepidosaurs), possibly as part of _Prolacertiformes_ ("The Prolacertiform Hypothesis"). Under the Ornithodiran Hypothesis, any feature seen in both crocodylians and dinosaurs would be expected to be present in at least basal pterosauromorphs. If, on the other hand, pterosaurs are non-archosaurian archosauromorphs, any feature seen in both crocodylians and
dinosaurs still *might* be present in basal pterosauromorphs.
Good point, archosaurmorphans, and even our extant member of the lepidosaurs, the Tura Tura, have embryonic diapause, and lay eggs. Prolacertiforms are often said to be closely related to the lepidosaurs, sharing some synapomorphies. Is it possible that the prolacertiforms diverged from an ancestor closer to a common ancestor of Lepidosauromorphs, Archosauromorphs, and squamates then presently hypothesized? If this ancestor had not yet developed embryonic diapause, then various prolacertiforms could have laid soft eggs, become viviparous, or developed hard-shelled eggs independently, as did the Gekkonidae. Turtles, interestingly, have embryonic diapause. At least some Ichthyosaurs and Mosasauroids are viviparous, demonstrating that they likely diverged earlier.
Thus far, hard-shelled crocodilian eggshell dates back to the Late Triassic, and represents the oldest known fossil eggshell. Dinosaurian: Preprismatoolithus, Spheroolithid, and Megaloolithadae show up in the Jurassic, and Ratite-Ornithoid in the Late Jurassic. Mr. Carpenter can correct me if this has changed. Although the timing works out right, I don?t know that there is of yet any proof that the crocodilian eggshell evolved into the dinosaurian types. Incidentally, fossil eggshell of the Geckonoid morphotype also dates back to the Jurassic. The pterosaur eggshell, if related, would presumably have diverged in the Triassic as well. Alternatively, pterosaurs could have developed a hard shell independently of crocodilians, as we know that turtles did.
I like the idea of David?s long-armed babes clinging to Longisquama. However, there are difficulties with the involvement of viviparity. Perhaps it need not be a factor.
Thus, eggs like those of crocodylians and dinosaurs are compatible with either hypothesis, and do nothing to resolve the relationships further.
I think that a electron microscope scan of a thin section of that pterosaur eggshell would be fascinating! It could shed some light on relationships by showing that it did or did not develop independently from other oospecies. Wouldn?t it be something if it has mammillae for example? Mr. Carpenter: get over there (and then call me to come look)!
Thanks,
Evan Robinson