Tag Info

Hot answers tagged

44

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). ...


35

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 ...


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 ...


16

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


13

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 ...


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 ...


11

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 ...


8

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 ...


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

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

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, ...


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

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

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 ...


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 ...


4

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 ...


3

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 ...


3

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 ...


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.


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.


2

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 ...


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

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

The data used in the graph you posted seems to be from Bambach. 2002. Supporting predators: changes in the global ecosystem inferred from changes in predator diversity (in Kowalewski & Kelley. The Fossil Record of Predation) - see fig 19b - and, if so, is specifically dealing with marine predators. I don't have time to look at that paper closely (it is ...


2

Apparently it wasn't. According to Wikipedia, A study that reported Dinosaur DNA was, mitochondrial cytochrome b sequences that had apparently been extracted from dinosaur bones dating to over 80 million years ago (reference). However, contamination was found in the reported study (reference). Don't expect too much because this is a close to ...


2

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

Encyclopedia of Life includes information on synonyms (see link for Apatosaurus) - not a list but searchable and often with references and background info. After a quick google search I also found this list from dinosaurcentral.com, but I don't know how credible and updated it is and it seems to lack references.



Only top voted, non community-wiki answers of a minimum length are eligible