53

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). ...


48

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 ...


24

In addition to kmm's excellent answer, I'd like to present the xkcd point of view. By any reasonable definition, T. Rex is more closely related to sparrows than to Stegosaurus. Separation by time Phylogenetic distance Physical similarity Birds aren't descended from dinosaurs, they are dinosaurs. Which means the fastest animal ...


20

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 ...


16

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 ...


15

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 (...


13

Yes, there are many early examples of ceratopsians before Triceratops. The oldest clear member of the lineage is Liaoceratops: "the oldest ceratopsian ever found ... was about the size of a large dog. It had a blunt beak and a dainty neck frill. ... Liaoceratops was a puny forebear of the feisty Triceratops. Size, horns and spectacular frills came later in ...


11

While it is true that some fossils can be radioactive, not all of them are. According to the ressources I have found, it depends on the place where these minerals are found and also the other minerals present at this place. When there are uranium and or potassium rich ores available, the fossils seem to enrich these radioactive isotopes in the calcium ...


10

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 ...


10

Yes, dodos were dinosaurs, but that probably doesn't quite mean what you think it does. Dodos were birds, closely related to pigeons. All birds are dinosaurs.


10

The answer is "one common ancestor", but I'll expand. All organisms descend from one common ancestor so that question is not quite well-posed, but what you are actually asking I think is whether birds all descend from one common ancestor that was a bird, or whether their common ancestor wasn't a bird, which implies that different branches of birds became ...


9

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 ...


8

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.


8

Richard Prum (the author of Evolution of feathers) says that ornithology is mostly a science about dinosaurs. He insists that dinosaurs were very close to birds, part of them had feathers and these feathered dinosaurs "shed (molt) them as birds of our days do". Thus, we can conclude that dinosaurs probably possessed at least one molting-like mechanism, ...


8

It's a sea urchin (Echinoidea). It looks like a specimen of Lovenia or another genus from the heart urchin (Spatangoida) family. What you see is just the shell without the spines. Lovenia woodsii Fossil sea urchin spines Image sources: http://www.thefossilforum.com/index.php?/collections/echinoderms/echinoids/lovenia-woodsii-r488/ http://www.fossilguy....


8

Per the comments, the actual paper seems pretty like a pretty straightforward operation of normal science: Somebody noticed something that looked off about one of the bones and decided they'd look into it more carefully. They found that yes, that bone appears to have been an accidental inclusion, and in fact the rest of the skeleton makes more sense without ...


7

Asides from flight-capable modern birds and their early ancestors1, there are several other therapod dinosaurs which palaeontologists suspect were capable of flight, "but in a manner substantially different from that of modern birds": Dromaeosaurids Microraptor Scapular orientation in theropods and basal birds, and the origin of flapping flight, Acta ...


7

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 ...


7

You're right that the authors don't comment on how they think the fossilization occurred. Since that process isn't the point of their article, my guess is that any discussion of it would have detracted from their research focus. There are some ways that soft tissue fossilization can occur, but to specifically answer your question as it relates to this case,...


6

Welcome to Biology.SE! Your daughter asks interesting questions! The question is debated. It is currently mostly thought that sauropods and pro-sauropods are sister lineages and therefore, one does not contain the other. In other words, the pro-sauropods are no more the ancestors of the sauropods than were the mammals are the dogs are the ancestors to the ...


6

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 dissimilar ...


6

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 ...


6

keratin and collagen are an incredibly tough molecules so if it is isolated from the environment (oxygen and bacteria) it could easily survive for that long. Not all proteins are equal some are very robust other very fragile. We have long known protein and carbohydrates can survive for incredible lengths of time under the right circumstances, amber is famous ...


6

I suppose that by the mass extinction, you are referring to the Cretaceous–Paleogene extinction event that happened 66 mya. The Most Recent Common Ancestor (MRCA) of all birds lived about 113.3 mya (early Cretaceous, according to this in oneZoom.org). So yes, the MRCA of all birds is definitely older than the Cretaceous–Paleogene extinction event. As you ...


5

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 ...


5

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 ...


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 stuck ...


5

Not a lot of people realize how extreme and how sudden the dinosaur's extinction was. Radiolab did an episode with several geologists about the extinction of the dinosaurs. Basically, when the meteor hit the Earth, a humongous amount of material was ejected into space, and most of it fell back down to the surface all around the planet. As it fell it left an ...


5

Spinosaurs (like Spinosaurus) are currently only known from 112-97 million years ago, although isolated teeth push the origin possibly back to ~150 Mya. At least now, there isn't any definite spinosaur material younger than 97 Mya. So spinosaurs were already extinct when the rest of the non-bird dinosaurs went extinct at the end of the Cretaceous, whether ...


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