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This is pretty much considered proven, not merely proposed.
In fact the "orthodoxy" has changed on this issue, and sauropods
are now pretty much considered to be terrestrial herbivores.
[Even conservative people like Dr. Martin have been convinced].
The evidence is quite persuasive, not only are there the anatomical
evidences that Bakker proposed (shape of the rib cage and so on),
and the breathing mechanics mentioned above, there is also the
fact that the Morrison formation represents a semi-arid habitat,
with little permanent standing water, so semi-aquatic animals
shouldn't be common - and sauropods are amoung the most common
animals in the Morrison beds.
> >COUNTER-ARGUMENT: Smooth rounded pebbles have been found through
> >and around rib fossils which could have been gizzard stones for
> >grinding large volumes of tough food as confirmed by the teeth.
> >Horizontal head and vertical neck in Diplodocus imply that its
> >neck was held nearly vertically during feeding at twenty to
> >thirty feet above the ground.
> Microscopic analysis of the dirt where the stomach of diplodocids
> would be has shown that the stomach contents was mainly pine
This may support Bakker's idea that diplodocids stood on their hind
legs while feeding. The alternative, that diplodocids were ground
level 'grazers' is hard to fathom, since I can see no reason to
evolve a long neck in that case. (Do *you* know of any living
Apatosaurus (ex Brontosaurus) *may* be an exception, as it is
a very odd diplodicid, heavily built (comparatively speaking),
and with a relatively short neck, so it is possible that this
genus abandoned trees and started eating ferns. In this case
the long neck would just be a 'vestigial' or retained ancestral
feature (for that genus only).
> >ORTHODOX: The two great dinosaur clans, the beaked dinosaurs
> >and the meat-eaters, evolved from quite different ancestors
> >(brontosaurs supposedly evolved from early meat-eaters).
> This has always presented a problem to me. I find it difficult
> to visualize how a species can change from herbivore to carnivore,
> or vice-versa. Try to imagine an Apatosaurus munching on pine
> and then suddenly deciding that he wants a Compsognathus for
> Or try to imagine a Tyrannosaurus having a fern salad for lunch.
This is not how it happens (and it *does*, since all mammals are
descendent from carnivorous stock). I bekieve the transition
occurs mostly in smallish forms, since frugivores often have sharp
teeth, and supplement their fruit diet with insects. Thus in this
size range the shift back and forth between frugivory and insectivory
appears to be fairly easy. And a shift from insectivory to carnivory
with increased size is fairly straight forward - and equivalently
for frugivory to folivory.
The basal stock of dinoasurs and pterosaurs is found in a series
of small forms, such as Lagerpeton, Lagosuchus, and Staurikosaurus.
>From this start it is fairly easy to get all of the known range
of anatomy of dinosaurs.
Again, this is an area where Bakker has been 'vindicated'. That
is a single origin for all dinosaurs is now pretty well established.
(At least until new evidence comes along :-))
Since Bakker's book was published, several new early ornithischians
have been discovered which are closer in anatomy to the basal stock
mentioned above. Also, the anatomy of herrerasaurs is better
understood. The differences between the ornithischians and the
saurischians no longer seem so great (especially after the
discovery of the Segnoaruia, with its mixture of ornithischian
and saurischian traits - apparently acquired convergently).
> >ORTHODOX: The dinosaurs died out because of a catastrophic
> >event such a large meteor.
> It's funny how just a decade or so ago this was the unorthodox
> It was thought at that time that dinosaurs were killed by diseases,
> or by mammals eating their eggs, and other silly ideas that are now
> coming back again. This is the one point in Bakker's book where I
> strongly disagree with him. It seems to me too much to swallow that
> it is just an incredible coincidence that a giant meteor or comet
> just happened to strike the Earth at exactly the end of the dinosaur
> age and deposit ash all over the world, but that it had nothing to
> do with the mass extinction.
Actually, there is much reason to question monofactorial explanations.
Also occuring at that time were the massive volcanic eruption
that formed the Deccan Traps in India. Is that a coincidence?
Also, it is not entirely clear that the dinosaurs died out at
the exact time of the meteor impact (assuming there was one).
There is some evidence from some sources that dinosaurs may have
been gone, or almost so, at the time of the impact. The same
can be said of some of the other groups that suffered at the K-T
boundary. Other groups, particularly certain planktonic groups,
show nearly instantaneous disappearence at the boundary.
This suggests a complex multi-causal process, including the
climatic effects of the Deccan volcanism, the meteor impact,
and perhaps the effects of the greatly reduced extent of the
inland seas (less continental shelf, more environmentally
uniform coastal plain).
Now, why that crack about 'if the impact occured'? Because
this weekend I read an article in a geological journal from
1993 that presented evidence that the Chixclub feature is *not*
an impact feature. They purported to show that the sedimentary
strata underneath the feature were not heavily deformed and melted
as would have been the case for an impact. If they are correct,
this pretty much rules out that site as a major impact site.
[I need to try to find follow-up articles to see where this
has gone since then].
> >Armor-plated nodosaurs have been found lying on their backs
> >embedded in the now hardened deposits left by the mud on the
> >sea floor at Como, Wyoming and Kansas. How did this occur?
> Perhaps they were washed out to sea in a flood?
Very likely. Post-mortem bloating can make even a very
heavy carcass capable of being floated out to sea in a strong
current. (The bloating is, after all, caused by methane
gas, thus lowering the density).
This is not really particularly mysterious.
> >The most common, large plant-eaters of the Late Cretaceous
> >were the duckbills without any sort of obvious defense. How
> >did the duckbills escape their enemies?
> Many of todays large herds of herbivores have no obvious defense.
> They survive by reproducing fast enough to replace their losses to
AND, they run fast. So, apparently, did the hadrosaurs.
Note, some hadrosaurs species are found predominantly in marsh
or swamp deposits, others are found mainly in estuarine deposits,
and the remainder are found widely in more terrestrial riparian
deposits. This suggests a wide range of ecological niches,
from moose-like herbivores mucking about in swamps and ponds
for aquatic plants (Edmontosaurus) to deer-like herbivores
browsing on forest scrub (?Corythosaurus).
> It's difficult for an amateur to judge the validity of all the
> different family trees proposed since the authors of most popular
> books never explain on what characteristics these groups are
Actually, many of the trees differ only in minor details. The one
presented here is pretty much the same as is widely used today.
The main differences are that the herrerasaurs are now recognised
as being more specifically ancestral to saurischians, or even
theropods, than to all the dinsoaurs. And, the "avian" theropods
are broken up into two or more groups. And, finally, that the
pachycephalosaurs are now thought (on very good grounds) to be
related to the ceratopsian line, not the thyreophoran one.
The minor differences, such as the podokesaurs being provisionally
placed in the Ceratosauria, do not mean as much, and are more
prone to future change anyhow.
> >"I use BRONTOSAURUS not APATOSAURUS even though, according to the
> >International Code of Zoological Nomenclature, the latter is the
> >legal name. Al Romer used to complain that "rules of nomenclature
> >should server the cause of science, not the other way around."
> Yes! I agree very strongly. The name change only served to confuse
> people. The name Brontosaurus had been used in hundreds of popular
> books for decades. No-one had every heard of Apatosaurus at that
> time. So, which name does it make more SENSE to go with?
Actually, the irony is that the name change was done in the 1910's
or 1920's, and simply *ignored* in the popular books until the
1960's! This is very similar to the fact that many popular
books on dinosaurs, expecially for young children, are still:
- portrayng sauropods as semi-aquatic
- drawing dinosaurs as splay-limbed, sluggish reptiles
both of which have been shown to be false portrayals.
It is simply the fact that popular books tend to copy material
from other popular books without checking that the information is
[Because the name change was ignored so long, some people got the
mistaken idea it was due to the change in the skull reconstruction,
which happened at the same time as the popular press heard about
the name change].
> I want to re-iterate that I agree with almost all of Bakkers ideas.
> Dinosaurs couldn't possibly have been as successful as they were
> (suppressing mammals et al for hundreds of millions of years) if
> they were slow, stupid, cold-blooded, etc.
Well, don't sell 'cold-blooded' short. In many environments it is
a better adaptation than endothermy - especially hot dry ones.
[Reptiles are still dominant, to this day, in desert environments].
Also, suppression of competitors is mainly accomplished by simply
'being there' - major adaptive radiations of new groups only occur
in the absence of *established* competitors.
Now, on the *slow* matter, I do agree.
Though, it does appear that dinosaurs were endothermic, since they
are found in arctic habitats where few other reptiles are known.
[For instance, in the Late Cretaceous, dinosaurs in the central
parts of North America shared the landscape with a giant crocodile
called Phobosuchus - similar dinosaurs are found on the north
slope of Alaska, *without* the crocodile].
The peace of God be with you.