The Palaeobiology Thread:

[tater]

Paleo classification is always gonna be odd, since it's entirely based upon what fossilization allows us to see. The study of fossilization, taphonomy, is one of the more fascinating aspects of paleontology to me because it makes us recognize that there is a filter on everything is important.

For feathers, we obviously need skin impressions, which are fairly rare to get compared to bones. If there was individual variation, or regional variation, sexual dimorphism, or based on age of the animal, you can see how hard it would be to generalize which critters get feathers with just a few data points of partial skin impressions.

Edited September 2, 2017 by tater

[Scotius]

Basically, paleonologists are trying to go from this:

To this:

You can imagine how much guesswork and extrapolation must be involved.

[tater]

They make that jump when they find feather impressions.

[Green Baron]

@Scotius, there is enough data at hand to (at least roughly) reconstruct past habitats and habitants. Palaeontology (P.) is more than just bones, though bones are mostly used to infer the phylogenetic tree. And indeed, many questions remain open, even regarding methodology.

P. is embedded in the geosciences with all their possibilities and they are vast. It is no problem to reconstruct past biocoenosises (besides bones) through sediment analysis, dating, isotopy, .... For example the conditions at time of deposit, flow direction and intensity (precipitation), environmental temperature, origin of the sediment and path it took, contents of the sediment like imprints of "biology", plants, seeds, etc. pp. allow, if present and thoroughly enough studied, quite an exact reconstruction. It is mostly details that are missing or questioned. Like colours, feathers or not, kinship, ...

As to bones and phylogeny, yep, problems are obvious. But once you have studied several skeletons and the morphology and functionality you quickly get an impression of how the vertebrate skeleton works. It is not that every time the "wheel" is reinvented, the basal "blueprint" (head, torso, extremities, etc.) is "only" adapted but the schemes are the same. Once you've seen different mammal tibiae for example you will most probably always recognize one, even if you don't know which animal it is from (reptiles and amphibians can be different have their own betraying traits).

So certain structures can be quite typical for certain animals and used to identifying them. Problem is that similar "requirements" lead to similar "solutions", meaning that a part of a skeleton might look similar to that of another animal because they filled a similar niche, but yet they lived 50 million years apart or on different halves of the globe (at that time). And that doesn't really make the lives of the P.sts easier.

I am not a specialist, i once (early 2000s) had to pass the examinations concerning the subject (and did so :-)). But of course things have changed since then and i have only very little practical experience.

 

Should you (or anybody on earth :-)) ever have the chance to visit one of those:

http://www.senckenberg.de/root/index.php?page_id=71&PHPSESSID=ap09jesv2p253jlopaoaqtenv7

http://www.naturkundemuseum-bw.de/intl/englisch/museum-am-loewentor

https://naturalhistory.si.edu/

https://www.fieldmuseum.org/

do so !

:-)

 

Edited September 2, 2017 by Green Baron

[tater]

Paleoecology is one area heavily influenced by taphonomy. What does the relative abundance of species tell you in the fossil record? It depends a lot on the mechanisms of fossilization. Do predators tend to die in locations that over or under represent them in the record? What about ecologies that don't lend themselves to preservation? We could assume that the world was swampy simply because swampy, muddy areas tend to leave fossils, and dry areas don't. 

One way to calibrate this (though with huge uncertainties, if they pay attention to that) would be to look at modern landscapes, and try to determine what % of dead animals could possibly leave fossils. This is the sort of modern study that is done in places like East Africa with good populations of large animals. I know from the couple safaris I did in Kenya that the ground is littered with bones. The trick is then to look at the frequency (mostly prey animals), and compare to the frequency of those that happen to die or are killed right next to a watering hole, drainage, etc, that could possibly be preserved, then estimate the % chance of those actually surviving into the future.

You'd need to do this for all kinds of potential landscapes like amazonian rainforests, alpine, etc.

Pat Shipman has an inexpensive overview book (textbooks on the subject are expensive). 

 

[Green Baron]

And the animals (i mean vertebrates) we find are those that were the most abundant top successful super duper cracks, and biased to the big ones. Those myriads of nature's tries that survived maybe a few hundred thousand years (still longer than us ;-)) or didn't have a large number and where put aside quickly as insufficiently fit are gone forever.

Smaller specimen sometimes bring bigger leaps forward as they remind us that there was more than big fat dinos.

 

[wumpus]

3 hours ago, Green Baron said:

@Scotius, there is enough data at hand to (at least roughly) reconstruct past habitats and habitants. Palaeontology (P.) is more than just bones, though bones are mostly used to infer the phylogenetic tree. And indeed, many questions remain open, even regarding methodology.

I'd be curious to know how much protein analysis changed biological views, especially in taxonomy.  It would give wonderful error bars to bone (and most other data you can get from fossils) analysis.  Note that while you can't reconstruct a dinosaur from ancient DNA, I'm sure they can often give a yes/no answer about if they are closer to reptiles or birds.

Also don't forget https://www.amnh.org/ for museums in America (I've been to the other two as well and they are on a similar level).  Unfortunately I can't say I've been to any on that level on the west coast, even though I'd highly recommend Balboa Park in general (Cincinnati has an astonishingly good natural history museum, but I doubt they really have enough room for paleontology).

- note: the Smithsonian dinosaur exhibit is closed for at least a year.  That should leave an "ancient oceans", "ancient plants", and "ancient mammals" halls of similar size (although only a single story due to smaller exhibits) for paleontology, but the impressive stuff isn't available.

[tater]

You'd have to have DNA from dinosaurs. You can get frozen mammal DNA, but not fossils.

[mikegarrison]

12 hours ago, Green Baron said:

Cladistic, with all it's dis- and advantages, is the classification technique. Sometimes (as in the case above) an index of a bone is used as a classification criteria. So all this is valid until it is replaced.

Yeah, there are limits to how well we can know this stuff. It's especially problematic when we find one branch that has attribute A but not B, and we find another branch that has B but not A, and then we find a later species that has both B and A. So maybe either B or A developed independently twice, or maybe there was a common ancestor to all of them that had both B and A, and the first two branches each lost one attribute.

[kerbiloid]

16 hours ago, Scotius said:

Basically, paleonologists are trying to go from this:

And even this:
 

Spoiler

to

When the future paleontologists will be finding primate jaws with metal and ceramic teeth, there will be even more nice ideas.

[Scotius]

Well, at least they will know we were sapient and technologically and socially advanced somewhat

[mikegarrison]

http://www.besse.at/sms/evolutn.html

There were many "missing links" between the earliest ancestral apes and modern Homo Sapiens. Scientists learn about these extinct species from fossil remains.
Here is an example (at left) of a fossil found near the famous "Lucy" fossil discovery. It is the skull of an australopithecine male, named "Desi" by its discoverers. Another couple, named Fred and Ethel, were found in a nearby cave, but Desi is the best preserved specimen.
Scientists can learn much from a relatively small fragment of skeleton. From this fossil, it was deduced that Desi stood about four-foot seven inches tall, walked with a slight limp, disliked zucchini and was a registered Democrat.

Other fossil remains have yet to be reliably interpreted. (below)

 

Some text and illustrations from the classic Science Made Stupid by Tom Weller.

Edited September 3, 2017 by mikegarrison

[Green Baron]

6 hours ago, mikegarrison said:

Yeah, there are limits to how well we can know this stuff. It's especially problematic when we find one branch that has attribute A but not B, and we find another branch that has B but not A, and then we find a later species that has both B and A. So maybe either B or A developed independently twice, or maybe there was a common ancestor to all of them that had both B and A, and the first two branches each lost one attribute.

Nice example.

 

 

 

grmblgrmbltherearealwaysafewmockingbirdswhithoutunderstandinggrmblgrmbl

 

 

[Xemina]

On 9/2/2017 at 2:49 PM, Green Baron said:

Saurischia ("a pelvis like a reptile lizard") is the group, besides the Ornithischia ("a pelvis like a bird") under the clade of the Dinosauria that are assumed to be the ancestors of the birds. And T. rex is in the right branch that leads to the birds, guess which ? :-)

Funnily those with a pelvis like a reptile lizard, the Saurischia are the birdy ones.

Cladistic, with all it's dis- and advantages, is the classification technique. Sometimes (as in the case above) an index of a bone is used as a classification criteria. So all this is valid until it is replaced.

And, psst, Sauropods belong to the Saurischia, or am i wrogn ?

 

Edit: changed reptile to lizard to avoid action ;-)

Yes sauropods are saurischians. 

5 hours ago, mikegarrison said:

There were many "missing links" between the earliest ancestral apes and modern Homo Sapiens. Scientists learn about these extinct species from fossil remains.
Here is an example (at left) of a fossil found near the famous "Lucy" fossil discovery. It is the skull of an australopithecine male, named "Desi" by its discoverers. Another couple, named Fred and Ethel, were found in a nearby cave, but Desi is the best preserved specimen.
Scientists can learn much from a relatively small fragment of skeleton. From this fossil, it was deduced that Desi stood about four-foot seven inches tall, walked with a slight limp, disliked zucchini and was a registered Democrat.

 

Ahem, the modern Homo Sapiens Sapiens, don't you mean?

 

Also, what about mammuthus and meganuera? WHY dinosaurs?

Also, I like to call terror birds "failed dinosaurs" 

Edited September 3, 2017 by Xemina

[Green Baron]

37 minutes ago, DeltaVerb said:

 *snip* Homo Sapiens Sapiens, *snip*

Now we leave the Dinos behind *waveshand*

I am clearly on the side of those who call us a subspecies of Homo sapiens. I also see Neandertals as a subspecies, ergo Homo sapiens neandertalensis. This is debated, sometimes with arguments like "it must (not) be so it shall (not) be" but anyway they interbred and we all have a part of the Neandertal genome in us, and there is much more evidence than that, even skeletons that can be interpreted as having features of both subspecies (Lagar Velho 1).

[mikegarrison]

Did you guys not realize that text was from a science parody book?

I know the references to Lucy, Desi, Fred, and Ethyl are almost fossils themselves these days, but I thought it was still pretty obvious even if you didn't get the reference.

Edited September 3, 2017 by mikegarrison

[kerbiloid]

15 hours ago, DeltaVerb said:

Also, I like to call terror birds "failed dinosaurs

Failed?!
 

Spoiler

Survavilists?

NO!

Surviving 65 mln years before it became mainstream.

T.rexes are losers, birds are winners.

 

7 hours ago, mikegarrison said:

Lucy, Desi, Fred, and Ethyl

Looking forward to season 2.

[Green Baron]

What is this about ?

[Xemina]

On 9/4/2017 at 7:14 AM, kerbiloid said:

Failed?!
 

  Reveal hidden contents

Survavilists?

NO!

Surviving 65 mln years before it became mainstream.

T.rexes are losers, birds are winners.

 

Looking forward to season 2.

1

You don't get the picture, do you? I like to call Gastornis a failed dinosaur, though dinosaurs were failed birds, because it was a bird that acted like a dinosaur. But in turn, birds wouldn't exist if the dinosaurs didn't get extinct, and that was a 50-50 chance, so there was a 50% chance we wouldn't exist.

Anyway, ready for Mammuthus talk? 

Edited September 5, 2017 by Xemina

[Xemina]

Anyone?

 

[kerbiloid]

Mammuthus is an elephant from Siberia...

Spoiler

...and from Siberia 2.

 

Edited September 30, 2017 by kerbiloid

[Green Baron]

To be precise (and link this to Palaeobiology), the first species of Mammuthus actually have afaik their origin in early Pleistocene Africa under a much warmer climate than late Pleistocene/early Holocene Siberia. They are among the species that roamed the open steppes, like wild horse(+), reindeer, ...

The last island populations of the cold adaption Woolly Mammoth (M primigenius) retreated into Siberia, which didn't save them from becoming extinct :-).

[NSEP]

On 04/09/2017 at 9:18 AM, DeltaVerb said:

Anyway, ready for Mammuthus talk? 

Teeth of Mammuthus sometimes wash up on the coast where i live close to, never witnessed that or heard it on the news though. I live only a few kilometers away from Doggerland.

[Green Baron]

On 30/09/2017 at 3:04 PM, DeltaVerb said:

Anyone?

 

Hmm. Ok.

Dinosaurs are no birds, not even failed ones. Birds are these flight able animals with (asymmetric - profiled) feathers and a beak. First real birds are from late Cretaceous times.

(One of) The current hypothesis (there were two others, now deprecated, but i let you do research) is that birds (Aves) stem from Theropods (see: Deinonychus). So, with some goodwill, you could say that a line of the dinosaurs has evolved into cute little birdies.

Edited October 2, 2017 by Green Baron

[Xemina]

I know, I know. I believe in that.

Question: Do you hate it when people say that dinosaurs didn't have feathers 'cus they want their JP dinos back? 'cus I do.

Also, with the T.rex skin thing - "Woohoo! T.rex didn't have feathers! Woo!" - When it was more like - "Okay, looks like T.rex did not have feathers in this location, so it was probably covered in feathers, still, but not there.".