Re: 2002 (bio)ontology papers AND Jim Carey's ongoing project on extinctions

Although there is little question about the juxtaposition in geological time of the dinosaur extinction and the world-wide impact of an asteroid collision, no one has provided a plausible explanation of how this extinction might have occurred from an ecological and life history perspective.

When all ecosystems are destroyed, normal ecology may not have to say much... real question: why should life history be so important?

The theory is effectively one of eradication -- the theory purports to explain how 100% of thousands of different species of dinosaurs went extinct due to the direct and indirect effects of the asteroid -- from the T. rex-sized dinosaurs to small insect- and seed-eating species,

No seed-eating species are known (though I can't speculate about what Gobipteryx did, for example).

from the desert- and forest-dwellers to the savannah- and marsh-inhabitants,

Were there any deserts in the Maastrichtian? Was there any such thing as a savannah anytime before the Eocene? Were there certainly marsh-living dinosaurs apart from some neornithine bird groups that survived? So maybe it's enough to explain how more or less all forests worldwide were devastated. A big impact can cause this, and there is ample evidence that gigantic wildfires happened.

from species inhabiting the tropics as well as those in polar regions.

What a difference.

the question of how every species of dinosaur could have become extinct worldwide due to this singular event while, at the same time, the extinction rates of other groups ranged from negligible (e.g., frogs, salamanders,

Is the fossil record of these groups good enough to allow any statistics?

placental mammals)

When "placental mammals" means the crown group Placentalia, I disagree because no certain member of that group is known from the Mesozoic. When "placental mammals" means Eutheria, I disagree likewise because of the diverse Asian clade of Eutheria that is known from the Coniacian to the Campanian or Maastrichtian but not from the Cenozoic (Zalambdalestidae + Asioryctitheria + Ukhaatherium + maybe Zhelestidae). Why doesn't one known Cenozoic eutherian have epipubes?

And then there is the diverse clade Djadochtatheria, a group of multituberculates with AFAIK the same range in time and space as the abovementioned assemblage.

to substantial, but far from complete (e.g., 20-70% extinction rates for turtles, marsupials, and ray-finned fishes).

Is 70 % of... what? Species? so far from complete?

All freshwater sharks of North America. All non-deep-sea coelacanths worldwide.

Asia had a lot of endemic turtle clades in the Mesozoic (look for Chinese family names and for Lindholmemydidae in www.fmnh.helsinki.fi/users/haaramo/Metazoa/Deuterostoma/Chordata/Reptilia/Parareptilia/Cryptodira.htm). All gone, though I don't know if exactly at the boundary.

In other words, why were the dinosaurs the only broad group to experience complete demise?

The ammonites are not going to be amused when they read that. Hippurites? Inoceramids? Plesiosauria and Mosasauroidea? All completely dead, with no descendants. Ammonitoidea certainly qualifies as a "broad group", whatever that is.

Not to mention the immense extinctions of plankton. Unfortunately I don't know anything about the internal taxonomy of Foraminifera and Coccolithophorida. Same for Echinodermata... there were those free-swimming crinoids like Uintacrinus before the K-T, right?

Or to reframe the question and assume (as do many contemporary paleontologists) that birds are living dinosaurs, why were the progenitors of modern birds the only dinosaurian group to survive the asteroid?

The Antarctic Connection sounds good to me. All birds killed off everywhere except in Antarctica, almost all birds killed off in Antarctica, and because all Antarctic birds were Neornithes in the Maastrichtian all survivors were Neornithes. Relies on negative evidence, though.

Maybe I can offer a more ecological explanation. Most of the few well enough known Enantiornithes, such as Avisauridae, were apparently arboreal, while no other known Maastrichtian bird was. Burn down all forests, and Enantiornithes is history. Ichthy- and Hesperornithiformes fed on fish that fed on plankton. Make a Strangelove ocean practically without plankton, and these bird groups are gone, too. Chicken- respectively tinamou-like birds, on the other hand, are expected to survive -- they live off whatever lives in leaf litter, and off seeds. They are, for maybe months, independent of primary production. Shorebirds (in the ecological sense) can likewise feed on survivors.

Not to mention the role of pure random once the world has crashed down and population sizes are minimal.

BTW, as long as it isn't completely clear on whom the burden of proof is, one must first answer the question "why not?".

Needless to say, the seminar should be fascinating, as Jim is a careful, methodical eco-entomologist, whose continuing research on the subject will result, I think, in a paper of far-reaching consequences. He does not deny the bollide event's effects on North American biozones, and he is not unaware of the paleoclimatic and oceanographic alterations being investigated by David Beerling et al. (rising and fluctuating sea levels

At least in North America, they didn't rise or fluctuate at that time, but AFAIK they fell steadily through 4 million years. Any new evidence here?

> environmental stresses on flowering plants herbivores

Therefore the gigantic mid-Oligocene mass extinction which almost reached the Permian-Triassic boundary in magnitude :-> :->

> meteorological patterns of some degree of ferocity).

AFAIK there's no evidence for ferocious climates around the K-T boundary, except for the very short heat wave mentioned onlist recently that is predicted by an impact.