2 questions...

[Sharptooth]

Assuming that the fossil record is complete. I don't think so.
We should also  take local trends into account. While there seems to be some decrease in NA Dinosaurs, those in Asia became more diverse at the same time.

Yep. Many people, paleontologists included, sometimes forget that our fossil record is VERY incomplete...

[DinoFan45]

It could be possible for pre archosaurs and sauropods to have feathers. In a national geographic from last year, it said that crocodiles had the gene for feathers, but it was inactive.

[SBell]

It could be possible for pre archosaurs and sauropods to have feathers. In a national geographic from last year, it said that crocodiles had the gene for feathers, but it was inactive.

That's because feathers are a modified scale.  And I wouldn't put too much stock in National Geographic articles--wait until something more definitive is published.

[CityRaptor]

I remember the article. It also linkened the "hair" of Pterosaurs back to the same source. Which ofcourse makes sene.

A feathered Croc would be interesting...

[Gryphoceratops]

I remember the article. It also linkened the "hair" of Pterosaurs back to the same source. Which ofcourse makes sene.

A feathered Croc would be interesting...

Dear genetics scientists,

Make it happen.  Thanks.

-Sincerely,

Me

[Metallisuchus]

Gwangi - I've noticed these things as well. That small size and/or the ability to fly = survival, to some extent. And here's a hole I've always noticed in Bakker's theory - dinosaurs were a very large group, just like mammals - lots of variety. The first thing anybody learns in virology is that there are very few diseases that can be transferred from species to species. I mean, sure, we can get something from a koala, but likely only as a carrier. I doubt a Triceratops, a Tyrannosaurus, and a marine reptile likely died from the same disease. I am suspicious however, of the abundance of angiosperms at the end of the Cretaceous, and how it could possibly relate to the mass extinction, if at all.

Stoneage - Thanks for providing the link. I think I'll read that when I'm in a more focused state of mind. Right now, I'm starving & stressed, so anything beyond these light paleo discussions is too much for me right now.

SBell - I've long wondered if feathers were advanced scales. I did see a documentary in very recent years that disputed this claim though. I'm no expert, especially in this area, so I cannot form an educated opinion - just throwing it out there.

Lol Grypho

[Gwangi]

Gwangi - I've noticed these things as well. That small size and/or the ability to fly = survival, to some extent. And here's a hole I've always noticed in Bakker's theory - dinosaurs were a very large group, just like mammals - lots of variety. The first thing anybody learns in virology is that there are very few diseases that can be transferred from species to species. I mean, sure, we can get something from a koala, but likely only as a carrier. I doubt a Triceratops, a Tyrannosaurus, and a marine reptile likely died from the same disease. I am suspicious however, of the abundance of angiosperms at the end of the Cretaceous, and how it could possibly relate to the mass extinction, if at all.

Angiosperms were already present in the Jurassic period and if I'm not mistaken one of Bakker's theories is that dinosaurs essentially "invented" flowers. I think by the time the Cretaceous ended there were a lot of herbivores adapted to a diet of angiosperms. This of course would not explain why small predators like dromaeosaurs died out.

As for feathers and scales. It is my understanding that the two are quite different from each other. That is also the consensus in that article I posted some pages back. The same article claims feathers are much more similar to scutes which are the bony armor-like scales found on the feet of birds as well as on crocodiles and turtles.

Then there is also this...

The proteins that make feathers in living birds are completely unlike the proteins that make reptilian scales today. Feathers originate in a skin layer deep under the outer layer that forms scales. It is very unlikely that feathers evolved from reptilian scales, even though that thought is deeply embedded in the minds of too many paleontologists. Feathers probably arose as new structures under and between reptile scales, not as modified scales. Many birds have scales on their lower legs and feet where feathers are not developed, and penguins have such short feathers on parts of their wings that the skin there is scaly for all practical purposes. So there is no real anatomical problem in imagining the evolution of feathers on a scaly reptilian skin. But feathers evolved in theropods as completely new structures, and any reasonable explanation of their origin has to take this into account.
http://mygeologypage.ucdavis.edu/cowen/historyoflife/feathersandflight.html

EDIT: As for extinction I'll have to do some more research on the issue. If sbell has some papers he would like to share I would appreciate it. Until then the asteroid theory is as sound as any. Also, I see a claim that dinosaurs died out before the impact but if that is the case we're forced to find a new theory and such a claim confuses me as I'm sure I've read some papers discussing dinosaurs found above the KT boundary.

[stoneage]

The K-T boundary is a clearly demarcated layer in the sedimentary rock of the Earth's crust. Below it is a zone about 10 feet thick often called the "three-meter gap" because of the lack of fossils found there. Scientists who believe the dinosaurs were in gradual decline pointed to this gap as support for their theory: If the dinosaurs lived right up until the asteroid hit, where were the fossils?

[Gwangi]

The K-T boundary is a clearly demarcated layer in the sedimentary rock of the Earth's crust. Below it is a zone about 10 feet thick often called the "three-meter gap" because of the lack of fossils found there. Scientists who believe the dinosaurs were in gradual decline pointed to this gap as support for their theory: If the dinosaurs lived right up until the asteroid hit, where were the fossils?

Firstly...sorry I referred to you as sbell in my last post, I got your two names mixed up.  Secondly though my question is this. Do fossils for other plant and animal species exist in this gap because if they do and dinosaurs don't I can see where you have an argument. If there are no fossils at all for any group of animals that went extinct or survived then this tells us nothing. Also, if not an asteroid impact what would you guess is the culprit in dinosaur extinction? Something happened that killed off so much life and I doubt it was disease or climate change. Are you suggesting the dinosaurs all went extinct before the impact and the impact did the rest of the damage? I find that highly unlikely.

There is also this, first link on a Google search for "three meter gap".
http://www.bbc.co.uk/news/science-environment-14137225
http://www.livescience.com/15011-dinosaurs-mass-extinction-catastrophic-meteor-strike.html

EDIT: There is also this.

Horner and Lessem (1993) state that no dinosaur remains are found within about 3 meters of the iridium band taken to represent the K-T boundary in Montana. They call this the three-meter gap, and suggest that it represents perhaps 100,000 years. Some have interpreted this as support for the position that the Cretaceous extinction was a gradual rather than sudden event. However, the 3-meter gap does not exist if one includes footprints. The youngest-known dinosaur fossils so far are actually a set of hadrosaur tracks found by Lockley and Hunt (1995, p. 23) in a sandstone shelf only 37 cm (less than 15 inches) below the iridium layer near Ludlow, Colorado, in the Raton Formation.

This discovery provides obvious proof that at least one group of dinosaurs was alive and well very near the end of the Cretaceous--and narrows the gap of missing dinosaur remains by an order of magnitude.

In fact, it may narrow the gap even more than that if the time frame rather than the sediment thickness is considered. The track bearing layers containing the hadrosaur tracks, which are rich in plant remains and thought to represent a coal swamp or peat bog environment. Based on sedimentation rates in similar environments today, Lockley and Hunt (1995) estimate the 37 cm may represent only a few thousand years or less. Additional hadrosaur tracks have also been found within the 3 meter gap, including a set 59 cm below the K-T boundary at the same site, and another Raton Formation Site about 12 miles south, which contains both hadrosaur and ceratopsian tracks within 1 or 2 meters of the K-T boundary (Lockley and Hunt, 1995).

SOURCE
http://paleo.cc/paluxy/maps97a.htm

[SBell]

The K-T boundary is a clearly demarcated layer in the sedimentary rock of the Earth's crust. Below it is a zone about 10 feet thick often called the "three-meter gap" because of the lack of fossils found there. Scientists who believe the dinosaurs were in gradual decline pointed to this gap as support for their theory: If the dinosaurs lived right up until the asteroid hit, where were the fossils?

Firstly...sorry I referred to you as sbell in my last post, I got your two names mixed up.  Secondly though my question is this. Do fossils for other plant and animal species exist in this gap because if they do and dinosaurs don't I can see where you have an argument. If there are no fossils at all for any group of animals that went extinct or survived then this tells us nothing. Also, if not an asteroid impact what would you guess is the culprit in dinosaur extinction? Something happened that killed off so much life and I doubt it was disease or climate change. Are you suggesting the dinosaurs all went extinct before the impact and the impact did the rest of the damage? I find that highly unlikely.

There is also this, first link on a Google search for "three meter gap".
http://www.bbc.co.uk/news/science-environment-14137225
http://www.livescience.com/15011-dinosaurs-mass-extinction-catastrophic-meteor-strike.html

EDIT: There is also this.

Horner and Lessem (1993) state that no dinosaur remains are found within about 3 meters of the iridium band taken to represent the K-T boundary in Montana. They call this the three-meter gap, and suggest that it represents perhaps 100,000 years. Some have interpreted this as support for the position that the Cretaceous extinction was a gradual rather than sudden event. However, the 3-meter gap does not exist if one includes footprints. The youngest-known dinosaur fossils so far are actually a set of hadrosaur tracks found by Lockley and Hunt (1995, p. 23) in a sandstone shelf only 37 cm (less than 15 inches) below the iridium layer near Ludlow, Colorado, in the Raton Formation.

This discovery provides obvious proof that at least one group of dinosaurs was alive and well very near the end of the Cretaceous--and narrows the gap of missing dinosaur remains by an order of magnitude.

In fact, it may narrow the gap even more than that if the time frame rather than the sediment thickness is considered. The track bearing layers containing the hadrosaur tracks, which are rich in plant remains and thought to represent a coal swamp or peat bog environment. Based on sedimentation rates in similar environments today, Lockley and Hunt (1995) estimate the 37 cm may represent only a few thousand years or less. Additional hadrosaur tracks have also been found within the 3 meter gap, including a set 59 cm below the K-T boundary at the same site, and another Raton Formation Site about 12 miles south, which contains both hadrosaur and ceratopsian tracks within 1 or 2 meters of the K-T boundary (Lockley and Hunt, 1995).

SOURCE
http://paleo.cc/paluxy/maps97a.htm

If you want to get technical, there is no K/T boundary--a revision of the 'Tertiary' period of the Cenozoic divided it into the Paleogene (.

Paleocene to Oligocene) and Neogene (Miocene to Pliocene). So the boundary is really the K/Pg

This has no actual bearing on the discussion at hand, but where else can it be brought up? My pointless knowledge is here to be shared!

But one thing I haven't seen much of is confirmation--a lot of discoveries get press, but something this extraordinary should be getting a lot of scrutiny (there have been several cases of supra-boundary dino fossils, but they were all eventually determined to be reworked in the sediments).

Plus, one fossil does not necessarily indicate a thriving community--areas where this exposure is well preserved really do need to be worked over with a fine tooth comb (hey, here in Saskatchewan we have K/Pg exposures all over the place, even in roadside ditches, but no one is really looking at them).

[darylj]

I see lityle reason to assume anything other than the meteor theory is the cause of the mass extinction at the end of the cretacious.
Perhaps some species were in decline, but id be more under the assumption that the fossil record is lacking because the earths surface took a battering for a few hundred plus years.
With regards to one set of hadrosaur footprints being found - i think thats more than enough evidence that this species was still present. especially when we are working in a world were the discovery of a tooth warrants a new species.

This does mean I have a little interest in the reworked discussion. As although I don't think it true I guess it is possible that some species survived passed the kf?

[stemturtle]

If you want to get technical, there is no K/T boundary--a revision of the 'Tertiary' period of the Cenozoic divided it into the Paleogene (.
Paleocene to Oligocene) and Neogene (Miocene to Pliocene). So the boundary is really the K/Pg

Tertiary officially went out of favor in 2004, two years after I took a paleo course.  Thanks for bringing us up to date, SBell.  I have much to learn.  This forum has enormous educational value. 

[Metallisuchus]

Gwangi - Yes, angiosperms were already present, but not abundant until the late Cretaceous (according to Bakker at least though I'm not sure if this is debatable). Don't underestimate the power of plants - they can affect predators as well - for 6 months during the spring/summer, my dog has allergies : )  Don't misquote me as saying that angiosperms killed off the dinosaurs though, I'm just curious how dinosaur life was changed by their new-found dominance. The world was already changing so much before the asteroid hit that you really have a lot to take into consideration.

Regarding feathers/scales... I thought you were of the opposite opinion. Thanks for the notes though. I think I read something similar a while back myself.

I've never heard of any dinosaurs (except birds...) above the K/T boundary, but I always felt that we might find SOMETHING one day.

AHH! Too many posts to respond to... Maybe DTF members could get together and make some dino-docs one day, or film a paleo-discussion.

EDIT: I don't know if anybody previously posted this...

http://www.sciencedaily.com/releases/2012/05/120501134159.htm

[Gwangi]

But one thing I haven't seen much of is confirmation--a lot of discoveries get press, but something this extraordinary should be getting a lot of scrutiny (there have been several cases of supra-boundary dino fossils, but they were all eventually determined to be reworked in the sediments).

Plus, one fossil does not necessarily indicate a thriving community--areas where this exposure is well preserved really do need to be worked over with a fine tooth comb (hey, here in Saskatchewan we have K/Pg exposures all over the place, even in roadside ditches, but no one is really looking at them).

Like I asked before, are there other fossils in this "three meter gap"? Nothing I read states if there is or isn't. If there is a rich sample of plants and non-dinosaurs I might buy into the theory that dinosaurs were already gone. It just doesn't add up for me and I'm not convinced by this gap, especially since fossils have apparently been found and the fossil record is sketchy as it is.

Gwangi - Yes, angiosperms were already present, but not abundant until the late Cretaceous (according to Bakker at least though I'm not sure if this is debatable). Don't underestimate the power of plants - they can affect predators as well - for 6 months during the spring/summer, my dog has allergies : )  Don't misquote me as saying that angiosperms killed off the dinosaurs though, I'm just curious how dinosaur life was changed by their new-found dominance. The world was already changing so much before the asteroid hit that you really have a lot to take into consideration.

The world was changing but I don't think it was changing at such a pace that the dinosaurs (who were certainly adaptable) couldn't keep up. It's not like one day the dinosaurs woke up and found all the vegetation replaced. The rise of angiosperms was gradual enough that dinosaurs no doubt evolved to fill the new niches the plants created.

Regarding feathers/scales... I thought you were of the opposite opinion. Thanks for the notes though. I think I read something similar a while back myself.

What do you mean? I am all about feathers but I'm just saying, it doesn't seem they were all that closely related to your standard scales and likely did not evolve from them. That does not mean dinosaurs didn't have them, actually it supports the notion that they may have had both feathers and scales I would say.

[Metallisuchus]

Gwangi - No, I that's not what I meant. I meant that I thought you were of the opinion that feathers were advanced scales, but apparently you aren't.

[SBell]

No, there isn't much of anything in that gap that I'm aware of.  Which indicates either a very poor system of sampling, or that populations were so low (of everything) that the fossil record isn't very complete.

Or, the environment changed so much (say, rivers drying up, desperate scavenging, move from a depositional to erosional environment, etc all being affected where mountains were forming on the west side of North America) that fossilization just wasn't able to occur in the same way.  Maybe people are looking in the wrong places.

I would assume that there are at least a few people who are aware of this problem and are trying to reconcile it, but for now the evidence points to a paucity of faunas for a while before the event.  When good evidence appears to the contrary, that might change.  But it's the old axiom that absence of proof is not proof of absence (so no fossils doesn't necessarily mean no dinosaurs); but to expand the point it cannot be seen as proof of presence either (so, no fossils doesn't mean they were there either).

[Gwangi]

Gwangi - No, I that's not what I meant. I meant that I thought you were of the opinion that feathers were advanced scales, but apparently you aren't.

With the evidence I've seen and looked over it would seem they weren't advanced scales but feathers do seem similar to scutes which are certainly scale-like, maybe that is where the confusion came from.

[Gwangi]

No, there isn't much of anything in that gap that I'm aware of.  Which indicates either a very poor system of sampling, or that populations were so low (of everything) that the fossil record isn't very complete.

Or, the environment changed so much (say, rivers drying up, desperate scavenging, move from a depositional to erosional environment, etc all being affected where mountains were forming on the west side of North America) that fossilization just wasn't able to occur in the same way.  Maybe people are looking in the wrong places.

I would assume that there are at least a few people who are aware of this problem and are trying to reconcile it, but for now the evidence points to a paucity of faunas for a while before the event.  When good evidence appears to the contrary, that might change.  But it's the old axiom that absence of proof is not proof of absence (so no fossils doesn't necessarily mean no dinosaurs); but to expand the point it cannot be seen as proof of presence either (so, no fossils doesn't mean they were there either).

All very good points. It is all certainly interesting and if I ever made it into paleontology maybe I would examine this gap...getting into paleontology isn't going to happen for me though. I guess we'll just have to wait and see but even if dinosaurs were in decline I doubt they were gone before the asteroid impact and I feel certain they would still be here if not for said impact.

[Metallisuchus]

Or perhaps mammals ate all the dinosaur eggs that weren't in nests in trees 

[stoneage]

Actually it was gravity that killed the dinosaurs!