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32

Birds are both flying dinosaurs and flying reptiles. Yes, that's potentially confusing. To understand the apparent contradiction, you have to understand how modern classification of organisms works (phylogenetic systematics). Under the old (Linnean) classification system, Reptilia (reptiles) was an order and Aves (birds) was a separate order. Phylogenetic ...


32

TL;DR: There is a dearth of actual experimental evidence. However: there is at least one study that confirmed the process ([STUDY #7] - Myxococcus xanthus; by Fiegna and Velicer, 2003). Another study experimentally confirmed higher extinction risk as well ([STUDY #8] - Paul F. Doherty's study of dimorphic bird species an [STUDY #9] - Denson K. McLain). ...


19

Squamates Extant venomous snakes do have venomous ancestors. Fry et al. (2006) reported on finding venom toxins more broadly within Reptilia, beyond the well-known venomous snakes and the helodermatid lizards. They show that varanid and iguanid lizards also have venom toxins. The same group of authors (Fry et al., 2009) then reported on the use of venom ...


14

In addition to kmm's excellent answer, I'd like to present the xkcd point of view.


11

In general the answer is always the same: you construct a phylogenetic tree. In order to locate different species on this tree in relation to each other, you use various features to compare which species are more similar to each other than others. The best way of doing this is by comparing their DNA sequence, especially orthologous genes (i.e. genes common ...


9

Assuming that gravity was essentially the same (other answers to this question notwithstanding), very large dinosaurs were dealing with the same forces that they would today. There are two clades of dinosaurs in which gigantism evolved, Sauropoda (quadrupdeal sauropods) and Theropoda (including T. rex). Each "solved" the problem of large size in different ...


7

Many of them looked like little rodents. However, several distinct mammalian lineages were already present, including Monotremes, marsupials and placental mammals. Throughout the whole mesozoic era, mammals were already quite diversified! Also, even though most of the mammals that survived the K/T boundary were rather small, there were already some larger ...


7

Extending Konrad Rudolph's answer, research has been conducted into reconstructing the phylogenetic tree via protein sequence data of the T. rex (one of the latest living dinosaurs): C. L. Organ et al, Molecular Phylogenetics of Mastodon and Tyrannosaurus rex, Science 320 (2008), p. 499. They use a variety of standard methods for the phylogenetic ...


6

Answer is quite simple as from @Alan Boyd link. They are cold blooded and thus, can go out for hunt in cold, they need to stay put till they get some prey. So, it mainly depend on the temperature of the outside, I found this interesting paper on relation of body sizes and latitude. Body sizes of poikilotherm vertebrates at different latitudes ...


6

I'm not an expert, but I think that you have to be specific about the flying animals to which you are referring. Pterosaurs are not classed as dinosaurs, whereas modern birds are descended from theropod dinosaurs which is where feathers appeared.


5

I believe it is more of the fact that the organism gets stuck to the residual resin on the plant itself, and becomes encased and later fossilised in the amber. From LiveScience.Com: A host of bugs, fungus and other life forms have been found trapped in amber from the time of the dinosaurs. Bugs can become encased in amber if, while alive, they get ...


5

This is a question I have often heard and there is no one certain answer to it. There are several scientific hypothesis about the methabolism of dinosaurs, but none of them has been ever proved or completely disproved. Arts of methabolism First of all, the term "cold-blooded" and "hot-blooded" are not scientific. In biology the organisms are classified ...


3

You are talking about the mitochondrial eve and the chromosome Y adam. At some point there must be just one pair, though historically the evidence can be lost if there is a near complete extinction event. Current evidence for eve points to SE Africa.


3

Relating to your last comment on random fluctuations in survival, a recent theoretical paper by Lee et al. 2011 studies the effect of mating systems on demographic stochasticity in small population. No empirical data there though. Their main conclusion is that polygyny (in relation with sex ratio) can lead to high demographic variance, therefore lowering ...


2

No. No other group found in the fossil record after the K-T boundary (the extinction "event") descends from dinosaurs. It is likely that the extinction event was not itself instantaneous so if you wanted to be extremely picky you could argue that small numbers of individuals survived the K-T boundary but, apart from birds, none of these survivors went on to ...


2

Diagnosing extinct species is even more difficult than extant taxa (see this question). Because systematists describing fossil species (usually) only have skeletons, they compare to other fossils. You are correct that diagnosing a species from only a skeleton can be tricky. What defines what you call a genus, a species, etc.? How morphologically *dis*similar ...


2

A recent genetic analysis suggests that they were probably bigger that we thought before : http://www.newscientist.com/article/dn22343-mammals-ancestor-was-not-as-puny-as-we-thought.html


2

fossilworks.org and paleobiodb.org are reasonably good databases for fossil records. Paleobiodb has even got a map based view which is really convenient. Thank you.


1

Fossil records are fossil records. The people who use them to attempt to prove or disprove evolution use them to represent their causes in different ways, gleaning sometimes completely contradictory facts from the same bodies of information, sometimes even the same samples. It is my personal belief that evolution isn't ever entirely phyletic, I like to ...


1

I think the concept of adaptive radiation is what you may be thinking about, since adaptive radiations have been observed following historic mass extinctions. When organisms are placed in environments with low diversity (either due to mass extinction or the recent creation of the environment) they can undergo adaptive radiation. This generally occurs ...



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