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Sundry responses of Bois
Just to be clear--throughout this post I am arguing only that my
hypotheses are reasonable. I am not saying things actually exist as I see
them. I also realize that this is a risky time to throw these responses
in. I have been following the what is and isn't a good hypothesis
discussion. Perhaps that is a good frame of reference for these ideas.
Caitlin R. Kiernan said:
> It certainly seems unlikely that mammals posed no large-scale threat to
> dinosaurs until the Latest Cretaceous, when, you suggest, they somehow,
> suddenly, engaged in a world-wide egg-devouring binge.
This assumes that without an extra-terrestrial event, the paleo biota
should remain in unpunctuated equilibrium. However, some evidence suggests
the following sequence of events: 1. small dinosaurs disappear towards the
end--a reasonable hypothesis is that this was due to competition or
predation from new mammals and birds; 2. In any case, now that traditional
tormenters were gone, there was relaxation on size constraint for
mammals. Thus, things were not the same at the end as at the start of the
Cretaceous. In addition to size increase, dentition diversity increases.
About other contemporaneous extinctions Caitlin R. Kiernan said:
> We're looking at an event that decimated a huge portion of the world's
> zooplankton; it would seem we need a culprit somewhat more profound than
> egg-eating mammals.
And in the same vein, Brian Choo said:
> Not to mention the non-involvement of mammals in the destruction
> of ammonoids, many bivalve/gastropod mollusks (especially the reef
> building rudistids), most foraminifera and calcareous nannoplankton
> groups and many broad-leaved evergreen angiosperm groups (gnawed away
> by mammals?) - all of which just happened to buy the farm at about
> the same time as the dinosaurs
Lillegraven and Eberle comment in 1999 paper, that in the cross K/T strata
that they studied, the _only_ apparent change was the disappearance of
non-avian dinosaurs. I, and many paleontologists, find the Alvarez
explanation of dinosaur extinction very unsatisfying. My claim that
dinosaur extinction was more complex than this, perhaps involving many
synergistic effects, is not very controversial. My claim that an important
synergistic effect was predation is controversial. But I'm not sure why.
Caitlin R. Kiernan said:
> How could it conceivably ever be falsified? What sort of "proof" might
> be gathered to support the hypothesis, even indirectly.
Since the hypothesis is dependent upon several subsidiary hypotheses, it
should be easy to falsify. These are: dinosaurs were relatively ineffective
at concealing their nests and depended instead on active nest defense;
observable morphological changes in mammals increased the pool of
potential predators on nests and hatchlings; observable morphological
changes in birds increased the pool of potential predators on nests
and hatchlings; such adaptations increased the competiveness of
neornithines and also resulted in the gradual domination of
neornithines over enantiornithines toward the K/T; mammals and birds
today and throughout the Cenozoic have limited the evolution and
distribution of large egg layers; successful large egg layers depend on
grass (a concealing medium which did not exist at the K/T), or
wetlands; wetlands and grass are more effective mammal insulators than
other biomes; post K/T dinosaurs will be found. And more...
Couldn't I ask a similar question about evolution by natural selection?
Until recently it was untestable. The condition of untestability didn't
make it any the less convincing. Indeed, the variety of phenomena it seeks
to explain give it strength. And a quirk in any of these phenomena would
falsify it (someone has said, simply finding a bunny amongst the dinosaurs
would falsify evolution). If someone discovered big terrestrial egg
layers and mammals (particularly placentals) living in harmony--without
having to hide, I would run away
forever. But the egg laying way of life really does appear to be heavily
constrained by predation. This is at least an hypothesis worthy of
examination. This proposition is being actively studied in
birdland. Such studies should impact this discussion.
> (Alvarez provided an hypothesis) which could be falsified, for which
> direct evidence could be gathered, and that exhibits others
> characteristics of a healthy hypothesis, such as fecundity.
As I've tried to show by subsidiary hypotheses, mine is fecund, at least!
> The idea that dinsoaurs lost out to mammals is already an out-dated,
> failed explanation for the extinction of non-avian dinosaurs. Let it
> rest in peace.
As far as I know, the "out-dated" version was rather perfunctory (mammals
eat dino eggs). My version has many more bells and whistles. In any case,
age of an hypothesis is only relevant if new information has made it
>What seems most unbelievable about this hypothesis is that it requires
>mammals everywhere, all of a sudden and in concert, all across the world,
>from Australia to Africa to Asia to the Americas, in all kinds of
>environments, to suddenly became so dashedly efficient at consuming
>eggs that all the dinosaurs are extinguished at almost exactly (if not
>exactly) the same time!
No, only in the connected Northern Hemispherical continents, plus, probably
South America (which was also connected). These connections enabled the
spread of placentals immediately (within a million or so years, anyway)
after the K/T. The same routes, then, were available before the K/T! India
is controversial but some researchers claim it was connected in the latest
K/T (is there a record of dino extinction in India--I think not). And in
other continents there is no record of extinction. So, two hypotheses
survive: a) a bolide wiped out all dinos instantly; b) dinosaurs became
extinct at roughly the same time on the connected continents, but may have
become extinct at different times on other continents.
Jarno Peschier said:
Does anyone know when the first known relatives of _Vulpes_
emerge in the fossil record? And do foxes eat eggs...?
Yes, they do eat eggs--big time.
>To say that egg-eating is the only cause would be silly, as you say. But
>could it be included as one of a number of causes?
Yes. For example, a bolide-caused photosynthesis cessation may cause a
brooding or defending parent to have to stray further from the nest to gain
enough food. Predators could take advantage of that. Or, habitat loss of
prime nesting sites (Archibald notes that the draining of the inland sea
erased much of the coastal flood plain habitat) could have enhanced invasion
into wetland nests (in much the same way that predators have invaded core
nesting areas of the pothole region). I think extinctions always involve
these kind of complex interactions. As Van Valen has said: deciding which
factor is the cause can be a matter of taste. My point about nest
predators, though, is that this has remained an abiding selective force,
perhaps preventing the re-evolution of dinosaurs. In this sense, nest and
hatchling predation is both a proximate and an ultimate cause.
> I'd be intrigued if some
.>species with a high probability of egg-eating proliferated, maybe because
their >predators had become extinct.
>Is there any evidence this happened?
"High probability of egg-eating"ness is still a long way from being
Specifically, extant egg-eaters show no particular egg eating adaptations.
I would say size is important (but not for gape since several successful
predators simply knock eggs together). But this may interest you: "It is
intriguing to note that the projected rise of the modern mammals (from
molecular estimates) coincides with the disappearance of the smaller
dinosaurs, those most likely to have been in direct competition with the new
mammals (M.J. Phillips, unpublished)." From Bromham, L., Phillips, M.J.,
and D. Penny, 1999, Growing up with dinosaurs: molecular dates andf the
mammalian radiation. The Review of Evolutionary Ecology. 14, no. 3: 113-118.
>However, the birds mentioned as leaving discovered
>nests and the fact that turtles use the r strategy show that defensive
>behavior was not inevitable.
Animals have a keen sense of when to stay and when to fight. Rhea probably
only leave the nests when there is no hope of protecting it. They fight
viciously when there is (rhea have been observed striking at overhead
airplanes (probably believing them to be Caracara hawks!). But they depend
upon concealment to avoid predator contact. Turtle strategy was, I believe,
unlikely for dinos (despite cute scene in WWD). Firstly, most large turtles
lay in very out of the way places probably trying to minimize predation.
And they can do that because they can swim vast distances. Secondly, nest
attendance may have been universal in dinosaurs (at least it enjoys an
extant phylogenetic bracket). If true, this would be very different from
>Is it possible that at the K/T boundary
>environmental stress made some strategies more effective than others? Do
>you think that an analysis of how the K/T survivors defended their young
>might be productive?
Such an analysis supports my hypothesis. The vast majority of survivors
employed strategies of stealth rather than defense. In this sense, and
inasmuch as dinosaurs are still with us, it is the strategy, not the taxon,
which has disappeared--except for semi-aquatic niche.
>A well-respected hypothesis--that Australia is and has been relatively
>depauperate in large carnivorous mammals (Tim Flannery)--may keep my
>hypothesis alive here.
Ron Orenstein replied: Considering that your hypothesis seems to depend on
small egg->eating mammals, not large carnivores (and Australia certainly has
>including dasyures and bandicoots), I don't see why.
True. But see below.
Darren Naish said:
John Bois wrote...
>> A well-respected hypothesis--that Australia is and has been relatively
>> depauperate in large carnivorous mammals (Tim Flannery)--may
>>keep my hypothesis alive here.
>This statement is now about 15 years out of date.
But perhaps Flannery's observation, viz., that Australia is different from
any other continent in its relative infertility--that is, it has never
collided with other continents and hence the mountain building,
sedimentation, etc. that characterize other continents has been very limited
in Australia--is still germane. If Australia is both geologically and
taxonomically different, we should not be surprised to see differences in
the success and/or failure of different strategies. I realize this says
little about my hypothesis. But it does pose the following interesting
>In view of all these mammalian predators, many of which were quite
>likely able to eat eggs, why then has Australia also been home to more
>than 30 species of large lizard, many large and even gigantic snakes
(including >madtsoids - _Wonambi_ was stil around in the Pleistocene),
>an assortment of crocodiles, all of which nest on land, egg-laying
>monotremes and flightless birds?
I will offer the following assortment of facts. Maybe
they suggest an answer:
1. The biggest birds in recent history were found on islands depauperate of
carnivorous fauna. It is widely accepted that the "cause" of the
evolution of huge Moa on New Zealand is the absence of mammals. Also, New
Zealand bird species with close relatives in Australia have longer
incubation times than their continental counterparts. This suggests that
predation pressure has an effect on the evolution of life history
strategies and that this pressure is different on different land
masses. Again, this would seem a
fairly intuitive statement.
2.In the same regard, Australia may be to Asia what NZ is to
Australia: the distribution of
nesting megapodes is apparently dependent on the make up of predatory
guilds--whether they are comprised of more Asian or Australian
taxa. Megapodes are
not known to nest on islands with Asian predators-e.g., cats. They will
nest on adjacent islands without those predators.
3. The largest and most diverse big bird faunas of Australia came after the
evolution of grass--a very effective concealing medium.
4. Emu are far less numerous on the Dingo-side of the Dingo fence; and at
the Tidbinbilla Nature Reserve the only observed predation was on nests and
5. Australia possesses the largest forest-nesting bird--the cassowary.
I suggest the answer to your question involves predator competence, predator
density, and prey concealment. These factors are undeniably different in
Oz. What are the alternate hypotheses? I mean, has anyone else proposed
hypotheses for this non-random distribution of large oviparous species.
>John Bois' theory is as redundant and illogical now as it was when he
>first started discussing it four years or so ago. Give it up John!
Do you suggest that extant nest and chick predators have little to do with
the success or failure of oviparous species? If you can show me this, I
will gladly give it up. In the meantime, I am grateful for your opinion.
Ron Orenstein wrote:
>To be perfectly fair to John (though I certainly do not accept his
>hypothesis) the one group of Mesozoic marine reptiles known to be
>live-bearing, the ichthyosaurs, apparently died out long before the end of
>the Cretaceous. Of course I'm still trying to figure out how
egg-eatingmammalian >predators (which presumably have been around since the
>not only wiped out dinosaurs at the K-T, but ammonites, rudist corals,
Rudists were also before, right? And ammonites suffered a Mesozoic-long
decline in their diversity. And marine extinction are yet to be correlated
temporally with terrestrial extinctions. As I argued earlier, the idea
that only one terrestrial animal taxon was affected--to the point of
extinction, anyway-- by the bolide, is a
challenge to the bolide as an explanation. And claims like: "They became
extinct because they were big" are strictly educated guesses. We have no
idea how a bolide might single out non-avian dinosaurs (apart from
untestable educated guesses, that is).
Betty Cunningham wrote:
>>This instect eater was not eating eggs or ganging up to eat eggs, at
>>least. What mammals from Mongolia or China are you referring to? Dr
>>Luo suggests all early mammals that we've found are insectivourous.
Stan Friesen replied:
>All of the early ones, certainly. But by the Latest Cretaceous things
>*were* beginning to change. Some of the largest marsupials and the largest
>placentals were getting beyond the size of insectivores, and so must have
>been at least somewhat broader in diet. And of course the
>multituberculates were granivores or omnivores.
And this does suggest a relaxation in the "lawn-mower" ecology, possibly
due to an earlier extinction of small dinosaurs.
>Still, none of these seem to me to have been likely threats to dinosaurs,
>even as egg predators. (Though I suspect that the "possums", at least, may
have eaten >eggs at times).
The reason Nessov's Cimolestes-like animal was so interesting to me is
_Cimolestes magnus_ (badger-size) is another likely culprit. Also,
are known from earliest Tertiary (meaning an unknown ancestor is yet to be
found in the Cretaceous). And birds may have been just as important in this
regard as they are today!
Stan Friesen wrote:
John Bois wrote:
>>(all?) mammalian egg-eaters are omnivorous. And yet, except in areas
>>where predator-density is relatively low (i.e., tundra, off shore
>>Islands), most (all?) oviparous species depend on concealment for
>>protecting their nest. This suggests that generalists are a sufficient
>>enough threat to keep extant oviparous species from laying in the open.
>Yes, but what makes you think dinosaur nests were never concealed? In
>fact, there are several known dinosaur nests that appear to have been
>buried, for example the ?troodontid nests Horner found, and all known
>sauropod nests, if I remember correctly. Burial is an excellent method of
Only if the parent doesn't give it away by its presence. My hypothesis
depends upon either nest attendance by most dinosaurs, or improved ability
in finding buried eggs. I would argue that it is very hard for a big
dinosaur to conceal anything. I claim that there is an upper limit in
size of parent for most
locations for the success of the lay-and-leave strategy, and that the
distribution of turtle species of different sizes supports that. In
addition, large eggs need lots of oxygen. This may only be available in
sand. Sand supports less vegetation and affords less concealment, i.e., a
large dinosaur leaves a large signature.
Martin Human wrote:
>TW, the Canada geese around here (west of Chicago) nest on the ground, in
>the open, in short read "neatly mown" by human or geese, in fact on any
>available patch of ground (including a 3 ft square in the middle of a
>They are available to all: modern efficient maammals such as cats, raccons,
>possums, dogs, rats, foxes, coyotes; birds such as crows, raptors, and for
>anyone else with an inclination.
If this were true on a large scale I would disappear in a trice. The geese
are (as Martin hypothesized in a subsequent message) possibly nesting there
because of a population explosion where primary nest sites are taken up. I
would also add leash laws, predator extirpation and the behavior of Canada
Geese, viz., they are unlike Snow Geese which show high fidelity to nest
in Northern Canada. These strategies must both have their payoffs.
However, I would argue that the Canada Goose strategy only pays off when
they happen to stumble into an area with low predator density (I
shouldn't say "stumble"--I'm sure they are incredibly careful
about where they nest!). Indeed,
waterfront restaurants near me employ a collie to keep geese off the lake
bank. It is an effective program. Forget nesting, the geese won't even
Finally, I forget who was asking about the phylogeny of viviparity in snakes
(whether it was derived from (mosasaur?) ancestors. All snakes likely
descended from oviparous species. See Lee, M.S.Y., and R. Shine. 1998,
Reptilian Viviparity and Dollo's Law. Evolution. 52(5):1441-1449.
I welcome comments. Thanks for your indulgence.