Seeds Saved Birds From Extinction

[Auspex]

Fossil teeth suggest that seeds saved bird ancestors from extinction.

"When the dinosaurs became extinct, plenty of small bird-like dinosaurs disappeared along with giants like Tyrannosaurus and Triceratops. Why only some of them survived to become modern-day birds remains a mystery. Now, researchers suggest that abrupt ecological changes following a meteor impact may have been more detrimental to carnivorous bird-like dinosaurs, and early modern birds with toothless beaks were able to survive on seeds when other food sources declined."

LINK

At first, I thought the idea weak, as the presence of teeth would not prevent the consumption of seeds. On thinking further, I realized that toothless bills were an adaptation away from carnivory, and so toothless avians were pre-adapted to the diet, where the meat eaters metabolisms were not. The mobility of flight no doubt played a role, too, but the obligate avian carnivores were still doomed.

[Oxytropidoceras]

Press Releases

New Royal Tyrrell Museum research investigates the pace of

the dinosaur extinction, and why birds may have survived

https://royaltyrrellmuseum.wordpress.com/2016/04/21/new-royal-tyrrell-museum-research-investigates-the-pace-of-the-dinosaur-extinction-and-why-birds-may-have-survived/

Bird-like Dinosaurs with Teeth Died Off Abruptly, Beaked

Birds Survived. Philip J. Currie Dinosaur Museum

https://dinomuseum.ca/wp-content/uploads/2016/04/Larson-2016-Bird-Dinosaur-Press-Release-PJCDM.pdf

Journal Paper:

Larson, D.W., Brown, C.M., and Evans, D.C. 2016. Dental disparity

and ecological stability in bird-like dinosaurs prior to the end-

Cretaceous mass extinction. Current Biology 26, 1–9.

http://www.cell.com/current-biology/fulltext/S0960-9822(16)30249-4

http://www.birdforum.net/showthread.php?t=323286

PDF Paper: http://www.cell.com/current-biology/pdfExtended/S0960-9822(16)30249-4

Attachment: http://www.cell.com/cms/attachment/2054006054/2060445977/mmc1.pdf

Yours,

paul H.

Edited April 22, 2016 by Oxytropidoceras

[ashcraft]

What about the insect eaters? Were any of them toothed? (If we can even know). Are all modern insect specialists evolved from seed eating survivors, or did they already control the niche by the extinction event?

My spider-sense is getting all tingly on this theory.

Brent Ashcraft

[Ridgehiker]

Fossil teeth suggest that seeds saved bird ancestors from extinction.

"When the dinosaurs became extinct, plenty of small bird-like dinosaurs disappeared along with giants like Tyrannosaurus and Triceratops. Why only some of them survived to become modern-day birds remains a mystery. Now, researchers suggest that abrupt ecological changes following a meteor impact may have been more detrimental to carnivorous bird-like dinosaurs, and early modern birds with toothless beaks were able to survive on seeds when other food sources declined."

LINK

At first, I thought the idea weak, as the presence of teeth would not prevent the consumption of seeds. On thinking further, I realized that toothless bills were an adaptation away from carnivory, and so toothless avians were pre-adapted to the diet, where the meat eaters metabolisms were not. The mobility of flight no doubt played a role, too, but the obligate avian carnivores were still doomed.

I'm not really up on the bird/ Dino thing.

However, today several orders of birds are meat eating predators. 'If' they were closely related to Dino raptors then odd that not one has tapped into its gene pool and evolved even rudimentary teeth. With the demise of dinos there was an ecological niche that was opened.

[Mediospirifer]

What about the insect eaters? Were any of them toothed? (If we can even know). Are all modern insect specialists evolved from seed eating survivors, or did they already control the niche by the extinction event?

My spider-sense is getting all tingly on this theory.

Brent Ashcraft

Lots of modern seed-eaters also eat bugs--most of them, I think, especially during breeding season. During the coldest time after the impact, I'd expect the surviving insects to go into hibernation. Small birds that already preyed on hibernating insects (along with insect eggs and seeds) might have done just fine, especially since many beaks besides raptors are capable of piercing flesh. Chickens can certainly draw blood, and I was told by a local game farm manager (raising ring-necked pheasants) that if they don't remove dead birds from the communal pens, the healthy birds will scavenge them!

I'm not really up on the bird/ Dino thing.

However, today several orders of birds are meat eating predators. 'If' they were closely related to Dino raptors then odd that not one has tapped into its gene pool and evolved even rudimentary teeth. With the demise of dinos there was an ecological niche that was opened.

Not really that odd. From what I've read, the gene for making tooth enamel is broken in modern birds. That's hard to undo--they'd pretty much have to re-evolve it from scratch. And, given that beaks can express all sorts of gripping or shredding surfaces, there isn't any selection pressure to do so. A new enamelin gene would likely go unused, and eventually get broken again.

There have been chick embryos that show tooth buds, but the trait is part of the expression of a lethal recessive trait, and none of the chicks have lived long enough to hatch.

Check out this thread on the efforts to re-develop dinosaurian traits in chickens: LINK

[Auspex]

Non-toothed bills work fine for eating insects, and birds in their current incarnation cannot afford the weight of teeth with no purpose. The raptorial bills on meat-eating hawks, eagles, and falcons is a secondary adaptive radiation.

[ashcraft]

What I was trying to say was that if any of the carnivorous toothed birds were primarily insect eaters, then the hypothesis has problems, as I think that insect eating beaked birds survived the impact. Chemically speaking, there is not much difference between a seed/nut and meat. I suspect that seed eaters switch to insects when they have young because insects are more plentiful at that time then seeds. This is different then predatory insects, like wasps, who primarily feed on sugar, but kill many insects to feed their young, because the young are growing, and need protein to reach adulthood.

Brent Ashcraft

[Ridgehiker]

Non-toothed bills work fine for eating insects, and birds in their current incarnation cannot afford the weight of teeth with no purpose. The raptorial bills on meat-eating hawks, eagles, and falcons is a secondary adaptive radiation.

True about weight but weight is only an issue because it is flight related. However, many species and various orders of birds are non flight land or sea predators.

Re seed eaters. As Ashcroft mentions, few birds are strict seed eaters. Most are omnivorous from chickadees to crows to grouse. They eat what's available and often feed young high protein diets...thus why so many migrate north with the explosion of insect life in Spring.

[Auspex]

The vast majority of toothed birds were of the clade Enantiornithes (the Hesperornithids being the others); all disappeared entirely at the K-Pg extinction. All the avians that survived are Neornithes, and are different enough from the Enantiorthes to possibly constitute a second genesis of what we call "birds", their lineage having diverged before any birds existed. Their dietary differences may have been a driving force in their divergence.

[Auspex]

Re seed eaters. As Ashcroft mentions, few birds are strict seed eaters. Most are omnivorous from chickadees to crows to grouse. They eat what's available and often feed young high protein diets...thus why so many migrate north with the explosion of insect life in Spring.

It is the obligate insect eaters that migrate from the tropics to the northern tiers; northern winters do not provide them with a food source. The obligate seed eaters do not migrate to the tropics, because food is available in the northern winters. Many of the seed eaters are opportunistic gleaners, but do not rely on insects for sustenance (though they have to feed their nestlings insects before they can handle seeds). Crows, jays, and ravens are the most omnivorous bunch.

[ashcraft]

The vast majority of toothed birds were of the clade Enantiornithes (the Hesperornithids being the others); all disappeared entirely at the K-Pg extinction. All the avians that survived are Neornithes, and are different enough from the Enantiorthes to possibly constitute a second genesis of what we call "birds", their lineage having diverged before any birds existed. Their dietary differences may have been a driving force in their divergence.

Very interesting. So modern birds make up a clade, but if you include all "birds" from the Cretaceous, they are not a natural group? Like "fish"? I believe there is some line of thought that bats have a similar history. The insectivorous bats evolved first, from a group that also produced rodents and primates, then the fruit bats evolved second, from a group that produced primates, but the rodents had already diverged.

I just don't know if diet can be tested though for the cause of extinction. Many mammals are obligate insectivores, and many are well toothed. In my ignorance of most things bird, it would seem more likely that it was simply random chance that allowed the beaked birds to survive, but not the toothed birds. I am assuming that the toothed birds and the beaked birds were equally diverse, meaning they both had species that were highly specialized, but they filled many niches. May be a false assumption though.

Brent Ashcraft

[Auspex]

It may be a case of "the beaked birds won" the competition to exploit the ecological environment, and this could have been food related.

If we accept the post-impact 'nuclear winter' scenario, then the durability of the seed crop vs. insects and the green vegetation they relied on may be what spared the modern bird lineage.

[siteseer]

Chas.,

I think the toothless bill was more an adaptation toward seed-eating in particular rather than away from flesh-eating because flowering plants diversified across the Cretaceous creating a huge new array of food sources (leaves, shoots, fruits, seeds) that also benefitted the plants (incompletely digested seeds getting distributed into new areas). An organism that could feed efficiently on seeds could still eat insects, small vertebrates, and even pick at a large carcass. The beak with a sharp tip could pick up seeds with precision. Even if a dromaeosaur wanted to pick up seeds, its teeth would likely have raked at them only to have them slip out between with perhaps just a few getting eaten while the bird filled up in the same amount of time.

It would seem seed-eating gave multituberculates (small mammals that occupied the niches that rodents have before there were rodents) an edge as well. They had teeth similar to rodents - good for gnawing and perhaps crushing seeds too. Mammals suffered during the K/T extinction as well but multituberculates survived and diversified during the Early Paleocene.

Jess

Fossil teeth suggest that seeds saved bird ancestors from extinction.

"When the dinosaurs became extinct, plenty of small bird-like dinosaurs disappeared along with giants like Tyrannosaurus and Triceratops. Why only some of them survived to become modern-day birds remains a mystery. Now, researchers suggest that abrupt ecological changes following a meteor impact may have been more detrimental to carnivorous bird-like dinosaurs, and early modern birds with toothless beaks were able to survive on seeds when other food sources declined."

LINK

At first, I thought the idea weak, as the presence of teeth would not prevent the consumption of seeds. On thinking further, I realized that toothless bills were an adaptation away from carnivory, and so toothless avians were pre-adapted to the diet, where the meat eaters metabolisms were not. The mobility of flight no doubt played a role, too, but the obligate avian carnivores were still doomed.

[siteseer]

Teeth are not just added weight. They require energy, so if start to lose them, that energy can go to other parts of the body. For birds that energy might have been routed to a further developing brain and other adaptations toward faster or more precise flying or greater intelligence and memory or faster and better digestion.

It's interesting that increasing toothlessness was also a trend among the pterosaurs across the Cretaceous. They had dwindled in diversity by the latest Cretaceous and I don't think any of the last of them had teeth.

True about weight but weight is only an issue because it is flight related. However, many species and various orders of birds are non flight land or sea predators.

Re seed eaters. As Ashcroft mentions, few birds are strict seed eaters. Most are omnivorous from chickadees to crows to grouse. They eat what's available and often feed young high protein diets...thus why so many migrate north with the explosion of insect life in Spring.

Edited April 30, 2016 by siteseer

[doushantuo]

Possibly i can fill in some gaps :

https://www.researchgate.net/publication/282646227_The_Origin_and_Diversification_of_Birds

https://www.researchgate.net/publication/51565941_A_gigantic_bird_from_the_Upper_Cretaceous_of_Central_Asia

https://www.researchgate.net/publication/226523720_Xu_X_et_al_A_new_feathered_maniraptoran_dinosaur_fossil_that_fills_a_morphological_gap_in_avian_origin_Chinese_Science_Bulletin

Edited April 30, 2016 by doushantuo

[doushantuo]

*cough*

Some flying /gliding animals other than "aviales" became extinct /are not found after the Maastrichtian

Phylogenetic insights and cladograms change by the day,by the way,what with what's coming out of China the last decade.

I am slightly skeptical about the whole thing,because we've got a long way to go towards coupling disparate and sparse knowledge about the relations between teeth,ethology,functional morphology and diet.

But that's just me

https://www.researchgate.net/publication/7288080_The_Development_of_Archosaurian_First-Generation_Teeth_in_a_Chicken_Mutant

Edited April 30, 2016 by doushantuo

[Ridgehiker]

I'm always cynical of these types of studies.

It's akin to using a few square kms of Austalia, the same in Madagascar, a mountaintop in the Himalayas..then extrapolating some theory on Ungulate taxonomy in the modern world. Perhaps fun but all interpreted on a haphazard set of woefully inadequate evidence.