New Theory Suggests Dinosaurs Were Already Dying When Asteroid Hit (phys.org)

The new "biotic revenge hypothesis" suggests that dinosaurs were killed off by toxic plants. (And an inability to recognize the taste of a toxic plant.) the gmr summarizes a new paper reported at Phys.org: The dinosaur population had been drastically decreasing before the asteroid impact, [and] the appearance of the first flowering plants -- angiosperms -- in the fossil record coincides with the gradual disappearance of the dinosaurs... The scientists concluded that though the asteroid played a role in the extinction of dinosaurs, the "plants had already placed severe strain on the species."
Crocodiles (believed to be descended from dinosaurs) also can't recognize the taste of toxic plants -- the researchers tested 10 different species. And they point out that not only did dinosaurs start to disappear before the asteroid impact -- they continued to "gradually disappear for millions of years afterward."

Comments

Crocodiles are dinosaurs - since when?

[willy_me]

A quick quote from Wikipedia,

As such, birds were the only dinosaur lineage to survive the Cretaceous–Paleogene extinction event 66 million years ago.

Crocodiles are not decedents of dinosaurs - they are reptiles. If this paper can not even see this then I can not put much weight into their theory.

Re:Crocodiles are dinosaurs - since when?

[AJWM]

Pro tip: don't believe everything you read in Wikipedia.

That's a vast oversimplification -- sure, trace a cladogram back far enough and you'll see something called Reptilia as the ancestor of both dinosaurs (and birds) and things ancestral to turtles, snakes and crocodilians. Dinosaurs are as much reptiles as birds are (indeed, birds are considered avian dinosaurs.)

Trace mammals back far enough and you come to synapsids aka "mammal-like reptiles" -- which aren't reptiles either.

Re:Crocodiles are dinosaurs - since when?

[Entrope]

Crocodiles are not descended from dinosaurs. They are related, as part of a group called archosaurs. Birds and crocodilians are (by the definition of Archosauria) the two surviving groups of archosaurs.

The reptiles most closely related to birds were the non-avian dinosaurs, but they are all dead. The most recent common ancestor of birds and crocodilians probably lived about 250 million years ago, so they are not that closely related.

Re:Crocodiles are dinosaurs - since when?

[clovis]

This is once again an example of Slashdot summary disease.
Summary says: "Crocodiles (believed to be descended from dinosaurs) also can't recognize the taste of toxic plants " etc

Except that the actual paper does not say that crocodiles descended from dinosaurs. This is what the paper says:

Since crocodilians are descendent from the same creatures that gave rise to dinosaurs, this creates the opportunity to evaluate the tenability of the proposition that dinosaurs went extinct due to an inherent inability to learn to avoid eating toxic plants

The funny thing about crocodiles is that they are evolutionarily less like lizards and are evolutionarily the closest living relative to birds and non-avian dinosaurs. Crocodilians evolved in the Triassic as part of the Archosaur group which is crocodiles, non-avian dinosaurs, birds.
So it's not completely ridiculous to use crocodiles in their experiment.

Re:A NEW THEORY!

[ShanghaiBill]

WOW! Someone made up more stupid RANDOM TRASH

Indeed. The paper is published by a psychologist, who is trying to psychoanalyse dinosaurs that lived 70 million years ago, when there is little evidence that psychoanalysis even works on living humans.

TFA contains some serious scientific illiteracy:
1. Dinosaurs are not "a species".
2. Crocodiles did not "descend from dinosaurs"
3. Plants would have no reason to evolve tasteless toxins, and there is no evidence whatsoever that they did.

Also, dinosaurs didn't go extinct. Some species died out, but other species survived. I have four small dinosaurs in my backyard, and they are very much alive. I keep them in my chicken coop, and their eggs are delicious. Much better than store-bought dinosaur eggs.

Ammonites?

[AJWM]

This may (although it doesn't, really) explain the decline of dinosaurs, but it says nothing about why thousands of other species (including all the ammonites) went extinct at the same time.

And the theory that dinosaurs were already dying off before the K/Pg boundary is hardly new. Part of that is an artifact of how fossils are formed and found. A species could have lasted several million years after its latest-known fossil, it just didn't happen to leave any fossils that have yet been found. (Conversely, the last surviving member of a species could have been fossilized. Unlikely though, except in the case of a mass extinction event.)

Re:survived for millions of years after

[clovis]

And they point out that not only did dinosaurs start to disappear before the asteroid impact -- they continued to "gradually disappear for millions of years afterward."

If dinosaurs survived for millions of years after the asteroid impact, then very clearly the impact did not kill them. The asteroid didn't kill the dinosaurs any more than the Black Death killed humanity. No, Trump will kill humanity. Trump will kill us dead. Trump!

There's zero evidence that dinosaurs existed after the asteroid. The article referred to by Slashdot, the Biotic Revenge Hypotheses has this citation for their "continued to survive" claim:
Sakamoto, M., Benton, M.J., and C. Venditti. 2016. Dinosaurs in decline tens of millions of years before their final extinction. Proceedings of the National Academy of Sciences 113(18):5036–5040

But the Sakamoto article says this about that: "The fossil record shows that dinosaurs existed to the K-Pg boundary but did not survive into the Cenozoic"

So, bzzzzt wrong answer.

Cool

[fahrbot-bot]

Anyone know if florists will deliver to Congress?

Rubbish, I know what happend.

[CaptnCrud]

First the Earth cooled. And then the dinosaurs came, but they got too big and fat, so they all died and they turned into oil. And then the Arabs came and they bought Mercedes Benzes. [McCroskey walks off] And Prince Charles started wearing all of Lady Di's clothes. I couldn't believe it- [Jacobs turns and starts to walk away, continuing to speak, trailing off as he gets further from the camera] he took her best summer dress and he put it on and went to town...

Re:survived for millions of years after

[vtcodger]

"There's zero evidence that dinosaurs existed after the asteroid"

Not zero. There's rather a lot of dinosaur material in early Paleocene strata in North America. The issue is whether it is (all) reworked from underlying cretaceous strata. In particular, a lot a folks think the saurian remains in the Ojo Alamo Formation in New Mexico are Paleocene . However, to my knowledge, no one has yet found an articulated Paleocene dinosaur skeleton. If articulated material is ever found, that'll probably settle the argument.

Re:A NEW THEORY!

[jeremyp]

First time I've heard anybody claim crocodiles are dinosaurs.

Because they are not. Dinosaurs and crocodiles are both archosaurs. But to claim one group is descended from the other is incorrect in much the same way as I am not descended from my brother.

Crocodiles are also not lizards. Lizards split with archosaurs before dinosaurs and crocodiles split. So crocodiles are not lizards in the same way as I am not descended from my cousin.

Re:Galileo's Square-Cube Law

[jemmyw]

The very first answer in the first link you posted answers the question:

<quote>Dinosaurs do not violate the square cube law.

Take the known strengths of bone and muscle, assume an animal shaped like the largest dinosaurs, apply the square cube law, and you get the maximum possible size and mass for an animal of that shape.

And, wait for it...

It turns out that maximum possible size and mass is just a tiny bit BIGGER than the biggest known dinosaurs!</quote>

Dinosaurs are a different shape to mammals.