1211: "Birds and Dinosaurs"

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Re: 1211: "Birds and Dinosaurs"

Postby gmalivuk » Mon May 13, 2013 2:34 pm UTC

Misanthropic Scott wrote:The article contains a proportional tree of life on this planet. The lengths of the branches represent number of species in the group. All three multi-cellular groups are just little twigs over on the right side of this enormous bush.
Is it proportional to number of species? I didn't see that mentioned when I skimmed the article.
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Re: 1211: "Birds and Dinosaurs"

Postby flekkie » Mon May 13, 2013 2:42 pm UTC

No one brought up the alt text from comic 1121, Identity yet?

(look at how 1211 and 1121 are just each others reverse!)

it says
'Not sure why I just taught everyone to flawlessly impersonate me to pretty much anyone I know. Just remember to constantly bring up how cool it is that birds are dinosaurs and you'll be set.'

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Re: 1211: "Birds and Dinosaurs"

Postby ensimismada » Mon May 13, 2013 2:56 pm UTC

wumpus wrote:...now I'm not sure if a blue whale might be closer related to a trout than a shark.

Your intuition is correct:
Time to most common recent ancestor of blue whale and trout: 400.1 million years
Time to MRCA of blue whale and shark: 462.5 my
I can't post links because my account is new and the message gets flagged as spam, but these data are from the TimeTree of Life, timetree.org.

kit wrote:1. What is the exact difference between "are descended from" and "are" in this context? Does it matter?


The "are" means that the taxon (an arbitrary, coherent unit of individual organisms, plural "taxa") in question is a member of a group. A group, in phylogenetics, is defined by a population and all of its descendents. This is known as a clade, or monophyletic group. If you don't include ALL of the ancestors, the group is no longer monophyletic, as you so rightly point out later on (cf. comic #867, again I can't link you :/). Most, but certainly not all, taxonomists try very hard to have names only apply to truly monophyletic groups and to do so the name must apply to a node on the phylogenetic tree and all of its descendents1. The descendents of the first dinosaur population don't suddenly stop belonging to the dinosaur group at an arbitrary timepoint.

Except when they do. The term anagenesis is used to describe a lineage changing from one species to another without branching into separate lines (cladogenesis). If there's enough gradual change in one line to warrant there being a dividing point between the "old" species and the "new," you have chronospecies. Not everybody agrees with this concept.

1. An example of a exception would be a population isolated on an island recently separated from the mainland by sea level rise. The ancestors of the individuals on the island came from the coastal part of a widespread mainland population. The island isolation was recent, to the island individuals are more closely related to the coastal mainland individuals than to the interior mainland individuals. Some would want to call the island individuals a new species because, say, they're a slightly different color and because it's reasonable to expect they won't exchange genes with any of the mainland species any more. But others would point out that renders the mainland species paraphyletic. What to do?

The Cat

Re: 1211: "Birds and Dinosaurs"

Postby The Cat » Mon May 13, 2013 2:58 pm UTC

Pegasaurus?


I wonder what a Pegasus with bat wings would look like...



The world is crazy when you look at it the right way. Which is good.


Yep, that is an interesting thought.

This one made me look after Pegasus and I found this http://en.wikipedia.org/wiki/Pegasidae.

Thank you.

Georg


Cheers!

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Re: 1211: "Birds and Dinosaurs"

Postby cellocgw » Mon May 13, 2013 3:03 pm UTC

Misanthropic Scott wrote:
More importantly though, I've got a great book suggestion for you.

Your Inner Fish: A Journey into the 3.5 Billion-Year History of the Human Body – Neil Shubin. This book explains a tremendous amount about the history of our evolution and how it has affected what we are today, including a variety of common health problems like bad backs, hernias, and the like, some of which stem from our fish heritage, most notably the hernias. I highly recommend this book for anyone interested in their own body. Oh, and for those who are looking for a less confrontational book on evolution than one from Dawkins, this one simply provides the facts. It’s pretty convincing and cool to say “well, we wanted to find an animal between these two, went to exposed rocks of the right age, and after a lot of searching, there it was!”


I second this recommendation. That's a very fun read.
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Re: 1211: "Birds and Dinosaurs"

Postby AugustePDX » Mon May 13, 2013 3:24 pm UTC

Quick, someone get this to Chris O'Dowd's character on HBO's "Family Tree." He's about to make a huge mistake.

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Re: 1211: "Birds and Dinosaurs"

Postby dsigned » Mon May 13, 2013 3:36 pm UTC

In my (amateur) opinion, the phyla have gotten all mixed up because of the whole genetic thing. Not that the genetic mapping is bad (clearly not), but I think the scientific community has been ill-prepared to react to some of the unexpected developments, such as the case that Randall pointed out in the comic. One example of this is the case of the crocodilians. The crocodilians, from a characteristic point of view, fit very closely with modern reptiles. Genetically however, crocodilians are closer to birds than to modern reptiles. The solution? Everyone's a reptile! "Reptile" now has almost no descriptive features. Reptiles can be either warm or cold blooded, have feathers or scales, have anything from a turtle to falcon bone structure, have a two, three or four chambered heart.

It would have made more sense to me to have labelled crocodilians a separate group, and kept the distinction between reptiles and birds.

I suppose it will all come out in the wash, as the distinctions will be made with other words, but it still seems silly to have taken such an important word in layman science and applied it to nearly every air-breathing animal that's ever lived.

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Re: 1211: "Birds and Dinosaurs"

Postby The Cat » Mon May 13, 2013 3:50 pm UTC

Did anyone think about the wings on a flying fish? Nearly insect wings. Trout like to eat mosquitoes, which are spawned from the water. Some dragonflys are worth study. Probably convergent evolution at it's finest. Kinda find convergent evolution interesting. 2 specific parts are the wing and foot. My focus being the lobe fined fish. Enduring the hostile environment of the ocean, undoubtedly sent the fish flying out of the water. Fun Undergraduate study.
Last edited by The Cat on Mon May 13, 2013 3:52 pm UTC, edited 1 time in total.

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Re: 1211: "Birds and Dinosaurs"

Postby ahammel » Mon May 13, 2013 3:51 pm UTC

dsigned wrote:In my (amateur) opinion, the phyla have gotten all mixed up because of the whole genetic thing. Not that the genetic mapping is bad (clearly not), but I think the scientific community has been ill-prepared to react to some of the unexpected developments, such as the case that Randall pointed out in the comic. One example of this is the case of the crocodilians. The crocodilians, from a characteristic point of view, fit very closely with modern reptiles. Genetically however, crocodilians are closer to birds than to modern reptiles. The solution? Everyone's a reptile! "Reptile" now has almost no descriptive features. Reptiles can be either warm or cold blooded, have feathers or scales, have anything from a turtle to falcon bone structure, have a two, three or four chambered heart.


If folk taxonomies clash with the actual evolutionary histories of taxa, that isn't really the systematists' fault.
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Re: 1211: "Birds and Dinosaurs"

Postby commodorejohn » Mon May 13, 2013 3:53 pm UTC

I'm sorry, Randall, but no matter how often you repeat the idea that birds being the descendants of dinosaurs is cool, that won't actually make it cool...
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Re: 1211: "Birds and Dinosaurs"

Postby chenille » Mon May 13, 2013 3:57 pm UTC

Misanthropic Scott wrote:Actually, I'm going to need to ask for a link to something backing up that claim about insects. They may be the most diverse group of animals. They are certainly not more numerous than bacteria.

The is very little nothing certain about species of bacteria; see for instance this article. You can find a list of currently described species here, and it's obvious much less than the number of insect species described even a long time ago.

Misanthropic Scott wrote:As for fish, it would make a lot more sense to use the Latin names for the taxa. We are in the taxa that includes lobe-finned fish, such as the coelecanth, and all tetrapods. The other group of fish, ray finned fish make up half of all vertebrate species.

I'm well aware of the phylogeny, and the many, many ways we reflect our descent from ray-finned fish. My point is that sharks and ray-finned fish have retained a lot of other features in common, which people shouldn't neglect simply because they are ancestral traits. From anything other than a strict phylogenetic point of view - ecological, biomechanical, medicinal, economical, and so on - it has proven very useful to treat them together, much more than to focus on the more technical features ray-finned fish share with birds, even if that's how they group on a cladogram. Refusing to allow even English words to reflect that is robbing yourself of useful concepts. Is that really so hard to see?
Last edited by chenille on Mon May 13, 2013 4:00 pm UTC, edited 1 time in total.

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Re: 1211: "Birds and Dinosaurs"

Postby Misanthropic Scott » Mon May 13, 2013 3:58 pm UTC

gmalivuk wrote:
Misanthropic Scott wrote:The article contains a proportional tree of life on this planet. The lengths of the branches represent number of species in the group. All three multi-cellular groups are just little twigs over on the right side of this enormous bush.
Is it proportional to number of species? I didn't see that mentioned when I skimmed the article.

You'll have to search for "Carl Woese" proportional tree of life for more details than are in this particular Gould article. There were more details in the Gould book in which I first saw this, if I remember correctly. Searching revealed that the named end branches are proportional to the numbers of species in each branch. The distances on the trunks between any two end branches are proportional to evolutionary proximity of relationship between the species. So, we are more closely related to slime molds, and they to us, than either of us is to diplomonads.

Sorry I still can't post links yet.

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Re: 1211: "Birds and Dinosaurs"

Postby tigerhawkvok » Mon May 13, 2013 4:02 pm UTC

. . wrote:Birds aren't descended from dinosaurs, birds ARE dinosaurs.
Humans aren't descended from reptiles, humans ARE reptiles.
Reptiles aren't descended from amphibians, reptiles ARE amphibians.
Amphibians aren't descended from fish, amphibians ARE fish.
Fish aren't descended from invertebates, fish ARE invertebrates.
Invertebrates aren't descended from sponges, invertebrates ARE sponges.
Sponges aren't descended from protozoa, sponges ARE protozoa.
etc.

Only the first is true.

Reptiles are the clade defined by the most recent common ancestor (MRCA) of _Gallus gallus_ and _Geochelone sulcata_ and all it's descendants.
Crown-group amphibians are defined as the MRCA of _Rhinella marina_ and _Boulengerula boulengeri_.
As I discussed earlier, "fish" are the clade actinopterygia. "Invertebrates" is paraphyletic, including all protostomes, echinodermata, and tunicates. That is a descriptive term, not a group of animals (much as "limbless" includes worms, snakes, and caecilians)
Protozoa and metazoa are different clades (sponges are a type of metazoan), defined primarily by multicellularity.

On the flip side, you can't define "dinosaurs" without incidentally including "birds". You just can't.

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Re: 1211: "Birds and Dinosaurs"

Postby chenille » Mon May 13, 2013 4:03 pm UTC

Misanthropic Scott wrote: You'll have to search for "Carl Woese" proportional tree of life for more details than are in this particular Gould article. There were more details in the Gould book in which I first saw this, if I remember correctly. Searching revealed that the named end branches are proportional to the numbers of species in each branch. The distances on the trunks between any two end branches are proportional to evolutionary proximity of relationship between the species. So, we are more closely related to slime molds, and they to us, than either of us is to diplomonads.

The Woese tree usually reflects genetic diversity rather than species counts, which are not the same thing. It's also rather frustrating how often it's still used, since it's based only on rRNA and makes some large errors, for instance placing all the eukaryotes without mitochondria near the bottom instead of with their closer relatives.

tigerhawkvok wrote:Only the first is true.
As I discussed earlier, "fish" are the clade actinopterygia. "Invertebrates" is paraphyletic, including all protostomes, echinodermata, and tunicates. That is a descriptive term, not a group of animals (much as "limbless" includes worms, snakes, and caecilians)
Protozoa and metazoa are different clades (sponges are a type of metazoan), defined primarily by multicellularity.

Fish have always been a paraphyletic group, taken as including lobe-finned fish, cartiligenous fish, and jawless fish; you can search for any of those terms and find a huge amount of literature. Protozoa are paraphyletic too - choanoflagellates are closer to animals, ciliates to brown algae, and so on. The idea that paraphyletic groups don't belong in taxonomy is rather recent, and has somewhat confused people; but at any rate the idea that they don't belong in English, and words like "fish" need to be redefined away from concepts people have found very practical, is silly.
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Re: 1211: "Birds and Dinosaurs"

Postby Misanthropic Scott » Mon May 13, 2013 4:12 pm UTC

chenille wrote:
Misanthropic Scott wrote:Actually, I'm going to need to ask for a link to something backing up that claim about insects. They may be the most diverse group of animals. They are certainly not more numerous than bacteria.

The is very little nothing certain about species of bacteria; see for instance this article. You can find a list of currently described species here, and it's obvious much less than the number of insect species described even a long time ago.

That is interesting.
Two people guessed that the Earth was home to between 10,000 and 100,000 species of bacteria; another five said between 100,000 and 1,000,000; while nine microbiologists put the put the upper limit at ten million species; eight guessed there were even more. Some consensus.

I agree we should be able to do better than this. However, I would also point out that another way to word exactly the same statement is that 17 out of the 24 people surveyed thought that there are around 10,000,000 species or more.

I guess that's why I usually hear the number 10,000,000.

I confess that I am surprised that so few are described species. But, remember that you picked insects because they are an old group of small and rapidly evolving organisms. That is why there are so many. Pure logic would dictate that a group 12 times older, a tiny fraction of the size, with a tiny fraction of the time in each generation, and that evolves even more rapidly than human culture can keep pace with, should be many many times more numerous than the insect world.

So, I will try to keep in mind that the number of identified and described species is so small. But, I can't help tempering that knowledge with both logic and the knowledge of the tremendous range of habitats inhabited by bacteria, including many kilometers underground in dry rock and miles beneath the ocean surface in the heat of volcanic vents.

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Re: 1211: "Birds and Dinosaurs"

Postby ahammel » Mon May 13, 2013 4:16 pm UTC

Misanthropic Scott wrote:
Two people guessed that the Earth was home to between 10,000 and 100,000 species of bacteria; another five said between 100,000 and 1,000,000; while nine microbiologists put the put the upper limit at ten million species; eight guessed there were even more. Some consensus.

I agree we should be able to do better than this. However, I would also point out that another way to word exactly the same statement is that 17 out of the 24 people surveyed thought that there are around 10,000,000 species or more.

I guess that's why I usually hear the number 10,000,000.
It is by no means clear what a species of bacteria even is, so, you know, that's a problem with estimating the number of them.
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Re: 1211: "Birds and Dinosaurs"

Postby Mr.Funsocks » Mon May 13, 2013 4:16 pm UTC

Hrng. I feel I gotta stick up for one of my professors (Dr. Nick Geist) who has done a lot of work that fairly conclusively shows that birds are NOT dinosaurs. I can't post links but if you look up his papers (like Lung Structure and Ventilation in Theropod Dinosaurs and Early Birds), he shows that while birds are definitely Archosaurs, they're probably more closely related to alligators than a T-Rex. They are not descended from dinosaurs. They share a common ancestor with dinosaurs.

Also, "grade" vs "clade". A grade is an evolutionary "state". It's not monophyletic and isn't a clade. For example, reptiles and fish are both a grade, but neither is a clade. Reptiles have scaley skin, are ectotherms, etc. But birds are distinctly different, though descended from, reptiles. So technically speaking, reptiles can't be a clade. They consist of some of the descendents of a common ancestor like squamates (lizards & snakes), turtles, crocodilians, pterosaurs, and dinosaurs, but not all the descendents that are distinctly different (birds). In the case of fish, as previously mentioned we would have to be in that clade, as we are descended from lobe-finned-fish (of which only a few species like chondrychthies survive). However it can be useful to talk about "fish" as a grade of evolution, not including things like tetrapods (us).

And we're not descended from reptiles, as a grade or clade. Our common ancestor with reptiles is before reptiles. We're both amniotes, but sauropsids (the reptile/amphibian line) diverged from synapsids (mammals) long ago. Pelycosaurs (our ancestors) may often be CALLED dinosaurs, but they had the beginnings of endothermy and no scales, so they definitely were not reptiles.

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Re: 1211: "Birds and Dinosaurs"

Postby chenille » Mon May 13, 2013 4:18 pm UTC

Misanthropic Scott wrote:But, remember that you picked insects because they are an old group of small and rapidly evolving organisms. That is why there are so many. Pure logic would dictate that a group 12 times older, a tiny fraction of the size, with a tiny fraction of the time in each generation, and that evolves even more rapidly than human culture can keep pace with, should be many many times more numerous than the insect world.

I picked insects because the vast majority of described species belong there, with beetles alone making up nearly a fifth. There are more than for instance crustaceans, echinoderms, and anemones all put together, even those are all older groups. So it presumably the difference reflects the number of distinct niches they have been able to occupy, rather than simply increase over time like your logic would assume.
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Re: 1211: "Birds and Dinosaurs"

Postby tigerhawkvok » Mon May 13, 2013 4:19 pm UTC

pappalink wrote:Cladistics is a funny thing, and can be arbitrary, depending on how old the terms used are and our resistance to change them. Currently monophyletic clades are the thing, and we're striving for them, but to do so would really shake things up. As implied earlier, for our own phyla, the chordates, to be monophyletic, we would have to be considered reptiles and mammals, and fish as well. Most people don't want to be considered reptiles though, so currently reptiles are a paraphyletic clade, which means that the common ancestor is a reptile but not all of the descendents are.


Not true at all. You just have to be careful about your definitions. If you define reptiles as the MRCA of _Gallus gallus_ and _Trachemys scripta_ and all its descendants, you're fine. Same thing if you define fish as actinopterygia. You just have to then accept you get some fuzzy zones with unclear terms (eg, "basal diapsids", "basal synapsids", "basal amniotes", "basal tetrapods", "basal sarcopterygians") for the things that don't fall neatly into buckets of descent.

Birds are another case - as of now they are not considered dinosaurs by the majority of the scientific community, making dinosaurs "paraphyletic", just like the reptiles. This can change however, and quite easily, by us getting together and saying "birds are dinosaurs". It's just naming after all. The common ancestor for birds was a dinosaur, and the common ancestor for dinosaurs was a lizard, etc.

Untrue on both counts. A bird is an inexorably a dinosaur as you and I are inexorably humans and inexorably mammals. You can't define that away.

Also, the common ancestor for dinosaurs was NOT a lizard. You're talking about something like Euparkeria, which is a basal archosaur. It's certainly not a lizard (which are squamates, a type of lepidosaur), with a whole host of features to differentiate it (hip joint, heart, skull structure, digits, neck, etc).

I personally like to think of birds as dinosaurs, which makes this, as Randall says, a "good world". Another interesting note - the stegosaurus and triceratops are both grouped into the clade "ornithischians", which means "bird hipped", while the t rex and dromaeosaurs (from which birds share a common ancestor) are in the clade "saurischians", which means "lizard hipped". So birds are in the "lizard hipped" and not "bird hipped" group :)

It is a good world indeed. More complicated and great than we could have ever dreamed up on our own :-)

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Re: 1211: "Birds and Dinosaurs"

Postby PolakoVoador » Mon May 13, 2013 4:20 pm UTC

Misanthropic Scott wrote:
chenille wrote:
Misanthropic Scott wrote:Bacteria really still reign supreme by every possible measure, number of species, number of individuals, and even by biomass.

By number of described species, insects trump everything. This might be because bacterial species are hard to recognize, but it might be genuinely the case that bacteria have diversified without separating into that many discrete species. To tell, you would need to define exactly what a species means in the case of asexually reproducing organisms capable of swapping DNA with completely unrelated groups, which is a difficult problem.

Anyway, bony fish are closer to birds than they are to sharks, but it's not unreasonable to call both them and sharks "fish", since they happen to share a ton of features birds lack. Yes, they're all ancestral features, but outside the narrow context of phylogenetics that doesn't make them less important. You could call Falco peregrinus a fast flying fish, but all that would do is reduce "fish" to a synonym of vertebrate, and make it harder to talk about them by neglecting the important ways birds have changed.

Now that may not apply to the case in the comic - considering how often people say "non-avian dinosaur" I think there must be some value in the concept, but it is hard to think of a lot uniting Tyrannosaurus and Stegosaurus. But the way it's drawn makes it look like the standard for "reasonable definitions" should be clades, which is more controversial than a lot of people recognize for taxonomy, and certainly a poor approach to giving names in English.

Actually, I'm going to need to ask for a link to something backing up that claim about insects. They may be the most diverse group of animals. They are certainly not more numerous than bacteria.

I've not posted enough on this board yet to enter links in my post, so arguing my point will be a bit harder. Please google the following and click the top link:

Planet of the Bacteria by Stephen Jay Gould

The article contains a proportional tree of life on this planet. The lengths of the branches represent number of species in the group. All three multi-cellular groups are just little twigs over on the right side of this enormous bush.

As for fish, it would make a lot more sense to use the Latin names for the taxa. We are in the taxa that includes lobe-finned fish, such as the coelecanth, and all tetrapods. The other group of fish, ray finned fish make up half of all vertebrate species.

More importantly though, I've got a great book suggestion for you.

Your Inner Fish: A Journey into the 3.5 Billion-Year History of the Human Body – Neil Shubin. This book explains a tremendous amount about the history of our evolution and how it has affected what we are today, including a variety of common health problems like bad backs, hernias, and the like, some of which stem from our fish heritage, most notably the hernias. I highly recommend this book for anyone interested in their own body. Oh, and for those who are looking for a less confrontational book on evolution than one from Dawkins, this one simply provides the facts. It’s pretty convincing and cool to say “well, we wanted to find an animal between these two, went to exposed rocks of the right age, and after a lot of searching, there it was!”


Here's the link, in case anyone is lazy to google it. Very fun read, by the way.

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Re: 1211: "Birds and Dinosaurs"

Postby thevicente » Mon May 13, 2013 4:23 pm UTC

>THis is a good world

I agree, but I am a little bit bothered by the fact the comic seems to imply it's because there are flying dinosaurs killin' prey etc

Also, anyome makes anything of the use of color in this one?

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Re: 1211: "Birds and Dinosaurs"

Postby ThAlEdison » Mon May 13, 2013 4:25 pm UTC

Goggalor wrote:I'm actually interviewing for a job as a raptor1 trainer tomorrow. I'm taking this as some kind of good omen.

1as in the bird-of-prey type of raptors, not the micro-,veloci-,utah- type raptors... unfortunately.


Wow, the discussion here was not what I was expecting. I was expecting at least one comment pointing out that being the fastest animal means it has the highest velocity. And as the above post mentioned, Falco Peregrinus is a diurnal bird of prey a.k.a. a raptor.

I don't know, I guess people felt it didn't need to be said. I wonder if they can be trained to open doors.

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Re: 1211: "Birds and Dinosaurs"

Postby tigerhawkvok » Mon May 13, 2013 4:28 pm UTC

chenille wrote:Fish have always been a paraphyletic group, taken as including lobe-finned fish, cartiligenous fish, and jawless fish; you can search for any of those terms and find a huge amount of literature. Protozoa are paraphyletic too - choanoflagellates are closer to animals, ciliates to brown algae, and so on. The idea that paraphyletic groups don't belong in taxonomy is rather recent, and has somewhat confused people; but at any rate the idea that they don't belong in English, and words like "fish" need to be redefined away from concepts people have found very practical, is silly.


I'll freely admit I never learned "fish" as including the jawless vertebrates (they were called that in grade school for me) or as I mentioned earlier, people calling skates, rays, and sharks "fish" in any serious context.

Lobe-finned "fish", yes, but that's why most systematicists I know will now call them fleshy-limbed vertebrates ;-)

It's great to make people redefine away from "practical" and "wrong". Once upon a time magnetism was tantamount to magic, and stars moved on celestial spheres, which was totally practical at the time but still *wrong*. We have a responsibility to help spread correct information and let people be better informed. What the bulk populace "knows" is stunningly scant when it's not a cat or dog. I have been, in all honesty, asked if:

1) Lizards are animals
2) Crickets are baby bats (sight, no labels)
3) Insects are animals
4) pretty much every lizard ever is an iguana
5) snakes have teeth

etc. At this point, I have no respect for "practical" or "common knowledge" and firmly believe that for the people that do know better we have an obligation to be nitpickingly accurate to maybe, just maybe, trickle some information about the world ... well, out into the world.

Thanks for the clarification on protozoa. I'm a metazoan man myself, and only broadly familiar with non-metazoans.

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Re: 1211: "Birds and Dinosaurs"

Postby HereBeUnmappedBits » Mon May 13, 2013 4:35 pm UTC

I'm surprised no one has brought up the alt-text for today's Dinosaur Comics.
Spoiler:
OKAY HERE'S A FUN THING TO LEARN ABOUT: space is only 350km up! This means that if 'xkcd' author Randall Munroe were put into an appropriate orbit, the vast majority of humanity would be closer to him than to Australia. This statistic applies to both physical distance, and emotionally.

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Re: 1211: "Birds and Dinosaurs"

Postby WriteBrainedJR » Mon May 13, 2013 4:37 pm UTC

tigerhawkvok wrote:On the flip side, you can't define "dinosaurs" without incidentally including "birds". You just can't.

Given the flexibility of language and the breadth of human creativity, I think statements in the form of "you can't say A without mentioning B," are almost always bad bets.

While I am willing not to argue with people who say birds are dinosaurs, the term "non-avian dinosaurs" fills me with rage. That term describes the vast majority of all dinosaurs that ever lived (and conventional wisdom says that it describes ALL the dinosaurs), and defines them as being "not this other tiny, short-lived minority group of dinosaurs that not everyone can agree are dinosaurs." It's the equivalent of some gilded-age anthropologist who classifies the world's various ethnic groups as being either "white" or "non-white."

Find a better word for it.

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Re: 1211: "Birds and Dinosaurs"

Postby ahammel » Mon May 13, 2013 4:41 pm UTC

WriteBrainedJR wrote:
tigerhawkvok wrote:On the flip side, you can't define "dinosaurs" without incidentally including "birds". You just can't.

Given the flexibility of language and the breadth of human creativity, I think statements in the form of "you can't say A without mentioning B," are almost always bad bets.
How about "the rules of modern systematics prevent biologists from defining a taxon which includes Stegosaurs and Tryranosaurs but excludes modern birds"?
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Re: 1211: "Birds and Dinosaurs"

Postby chenille » Mon May 13, 2013 4:44 pm UTC

tigerhawkvok wrote:At this point, I have no respect for "practical" or "common knowledge" and firmly believe that for the people that do know better we have an obligation to be nitpickingly accurate to maybe, just maybe, trickle some information about the world ... well, out into the world.

Yeah, but it's not like we're talking about how ignorant people describe things. Taking fish as including both cartiligenous and ray-finned groups is something biologists have done for a long time, and it's proved practical for discussing things like ecology and physiology because of features they share lost in tetrapod vertebrates. When you're calling it inaccurate, you're insisting everything has to be redefined in terms of phylogenetics, and no language should ever be based on anything else. I'd encourage you to reconsider that narrow perspective.

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Re: 1211: "Birds and Dinosaurs"

Postby WriteBrainedJR » Mon May 13, 2013 4:47 pm UTC

ahammel wrote:
WriteBrainedJR wrote:
tigerhawkvok wrote:On the flip side, you can't define "dinosaurs" without incidentally including "birds". You just can't.

Given the flexibility of language and the breadth of human creativity, I think statements in the form of "you can't say A without mentioning B," are almost always bad bets.
How about "the rules of modern systematics prevent biologists from defining a taxon which includes Stegosaurs and Tryranosaurs but excludes modern birds"?

That's certainly a more reasonable type of statement to make. However, there are plenty of scientists who do not consider birds to be dinosaurs, suggesting that the statement still isn't true. I'm certainly no expert in taxonomy, so I'll defer to the scientists.

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Re: 1211: "Birds and Dinosaurs"

Postby ahammel » Mon May 13, 2013 4:52 pm UTC

WriteBrainedJR wrote:
ahammel wrote:
WriteBrainedJR wrote:
tigerhawkvok wrote:On the flip side, you can't define "dinosaurs" without incidentally including "birds". You just can't.

Given the flexibility of language and the breadth of human creativity, I think statements in the form of "you can't say A without mentioning B," are almost always bad bets.
How about "the rules of modern systematics prevent biologists from defining a taxon which includes Stegosaurs and Tryranosaurs but excludes modern birds"?

That's certainly a more reasonable type of statement to make. However, there are plenty of scientists who do not consider birds to be dinosaurs, suggesting that the statement still isn't true.
Like who?

If there are, they're wrong, or at least they're ignoring the bulk of the current evidence.
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Re: 1211: "Birds and Dinosaurs"

Postby chenille » Mon May 13, 2013 4:58 pm UTC

I'd like to add this paper (pdf) as an example of someone who doesn't think classifications have to be about monophyletic groups, but argues that recognizing others allows them to better reflect evolutionary changes. The question is not as clear-cut as ahammel and tigerhawkvok are making it out to be.

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Re: 1211: "Birds and Dinosaurs"

Postby ahammel » Mon May 13, 2013 5:01 pm UTC

chenille wrote:I'd like to add this paper (pdf) as an example of someone who doesn't think classifications have to be about monophyletic groups, but argues that recognizing others allows them to better reflect evolutionary changes. The question is not as clear-cut as ahammel and tigerhawkvok are making it out to be.

It's a strong minority opinion, for sure, but the conferences on taxonomy these days mostly require monophyly.
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Re: 1211: "Birds and Dinosaurs"

Postby WriteBrainedJR » Mon May 13, 2013 5:04 pm UTC

ahammel wrote:
WriteBrainedJR wrote:
ahammel wrote:
WriteBrainedJR wrote:
tigerhawkvok wrote:On the flip side, you can't define "dinosaurs" without incidentally including "birds". You just can't.

Given the flexibility of language and the breadth of human creativity, I think statements in the form of "you can't say A without mentioning B," are almost always bad bets.
How about "the rules of modern systematics prevent biologists from defining a taxon which includes Stegosaurs and Tryranosaurs but excludes modern birds"?

That's certainly a more reasonable type of statement to make. However, there are plenty of scientists who do not consider birds to be dinosaurs, suggesting that the statement still isn't true.
Like who?

If there are, they're wrong, or at least they're ignoring the bulk of the current evidence.

According to an earlier post in the thread "the majority of the scientific community" doesn't consider birds to be dinosaurs. It was not disputed. When I read something on the xkcd board that goes undisputed, I assume it's at least partly true or thoroughly frivolous.

I don't know which scientists don't consider birds to be dinosaurs. I don't know which do, either. Like I said, it's not my area of expertise, and even if it were, I'm terrible with names, and also I don't really care. For the purposes of a purely scientific classification system, I think birds probably are dinosaurs.

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Re: 1211: "Birds and Dinosaurs"

Postby Kit. » Mon May 13, 2013 5:16 pm UTC

ensimismada wrote:
wumpus wrote:...now I'm not sure if a blue whale might be closer related to a trout than a shark.

Your intuition is correct:
Time to most common recent ancestor of blue whale and trout: 400.1 million years
Time to MRCA of blue whale and shark: 462.5 my

I'm not sure that "time to MRCA" is the correct way to determine "closeness" between populations of different effective sizes and of different evolutionary pressures.

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Re: 1211: "Birds and Dinosaurs"

Postby ps.02 » Mon May 13, 2013 5:23 pm UTC

Ah but don't forget that "scientist" is a taxonomic mess. For example, computer scientists, despite the name, may actually be more closely related to mathematicians than to what we might call true scientists or euscientists.

So the range of beliefs in the taxonomic or linguistic definitions of bird and dinosaur amongst "scientists" doesn't seem all that important. The real question, of course, is whether Vardaman's mother, in As I Lay Dying, really is a fish. Even if it's not clear from the text whether he is a scientist.

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Re: 1211: "Birds and Dinosaurs"

Postby Klear » Mon May 13, 2013 5:26 pm UTC

WriteBrainedJR wrote:I don't know which scientists don't consider birds to be dinosaurs. I don't know which do, either.


Alan Grant is one.

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Re: 1211: "Birds and Dinosaurs"

Postby Idhan » Mon May 13, 2013 5:30 pm UTC

If I say falcons are dinosaurs by cladistic rules, I'll also say dolphins are fish and gorilla are monkeys. No more "whales are mammals and not fish" or "gorillas are apes not monkeys."

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Re: 1211: "Birds and Dinosaurs"

Postby Kit. » Mon May 13, 2013 5:38 pm UTC

I have always thought that humans are monkeys. However, "humans are fish" is kinda new to me.

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Re: 1211: "Birds and Dinosaurs"

Postby keithl » Mon May 13, 2013 6:14 pm UTC

One reason for the emergence of therapods like T. Rex and the ancestors of birds may have been a large excursion in CO₂ between the Jurassic and the Cretaceous. A similar excursion occurs around the boundary of the Triassic and Jurassic. The flowering plants, angiosperms, began around the Jurassic/Cretaceous boundary, and the evolution of the C4 angiosperms (thrifty CO₂ users) like corn and apples began during the historically low levels of CO₂ over the last few million years.

While the times and CO₂ are still disputed (and I almost certainly got some wrong), it is possible that we are witnessing (and many say creating) conditions more like the J/K boundary excursion than our recent past, and evolution may respond with similar changes in the mix of species.

So perhaps those birds are just biding their time, ready to grow into megafauna when the conditions become favorable, while the bat and rat descendents of mammals descend back down into holes in the ground. Perhaps they will finally make Jurassic Park 4 - "they" meaning the neo-therapods of the distant future, with an anti-mammal POV.

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Re: 1211: "Birds and Dinosaurs"

Postby cellocgw » Mon May 13, 2013 6:14 pm UTC

tigerhawkvok wrote:
It's great to make people redefine away from "practical" and "wrong". Once upon a time magnetism was tantamount to magic, and stars moved on celestial spheres, which was totally practical at the time but still *wrong*. We have a responsibility to help spread correct information and let people be better informed. What the bulk populace "knows" is stunningly scant when it's not a cat or dog. I have been, in all honesty, asked if:

1) Lizards are animals
2) Crickets are baby bats (sight, no labels)
3) Insects are animals
4) pretty much every lizard ever is an iguana
5) snakes have teeth


Two thoughts:

1) on magnetism. You're probably familiar with the whole "Fucking magnets, how do they work?" ICP thing (sadly)
2) I'd say cricket bats are baby baseball bats :-)
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Re: 1211: "Birds and Dinosaurs"

Postby speising » Mon May 13, 2013 6:17 pm UTC

so, does anybody know if they still teach that dinosaurs died out in school? i guess this could be considered nothing but a trope by now.


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