Re: [Re: [Part 2: Terramegathermy (very long, too)]]

[archosaur@usa.net]

> The post that started this thread had 24 KB... is this so much? :-|

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Heh, yeah well when I wrote the previous reply to this post, it spilled over
from one notepad to another. I think I just have to snip more :)

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> > I don't get it. If we keep finding conflicting histological          > >
examples with each species studied,

> Do we? The most recent articles I know all agree that the species      >
studied grew very fast.

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Not from what I've read. Some studies show species with fibrolamellar bone
growth, while others show LAGs. Sometimes there is only a species difference,
maybe even a difference between specimens.

Here's a prime example:

A Chinsamy, T Rich, and P VickersRich, Polar dinosaur bone histology 
Journal of Vertebrate Paleontology, 1998, 18(2): 385-390  


Abstract (* emphasis mine):

We report on the bone microstructure of a hypsilophodont and an
ornithomimosaur from the Early Cretaceous, Otway Group of Dinosaur Cove in
south-eastern Australia, which at the time lay well within the Antarctic
Circle. Although subjected to the same environmental conditions, the
*dinosaurs exhibit different hone histology*. The hypsilophodontid shows a
*continuous rate of bone deposition*, while the ornithomimosaur has a
*cyclical pattern of bone formation*. We interpret these varying patterns of
bone microstructure as a reflection of different growth strategies of these
dinosaurs.   


So, did the ornithischian have fast growth rates while the coelurosaur had
seasonal ones? Who's the tachymetabolite here?

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> Not much. Mainly the argument from generational turnover: > *Deinosuchus*
needed 50 years to reach 10 m. If a sauropod would > already have been 100
years old when reaching _adult size_ (recent > articles say 10 years based on
histology), the populations would have > been endangered all the time, and the
fossil record would look > different (contain far, far less adult sauropods
and more younger > ones).

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Personally I have my doubts about the _Deinosuchus_ study (i.e. are osteoderms
reliable indicators of bone growth? Why not long bones or vertebrae?)

As for the sauropod pop, would we find more young? Adults have more time
friendly bones, young bones break easy and would have less of a chance of
fossilizing. I mean how many young _Deinosuchus_ fossils do we have? 

_Megalania_?

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> P&L suggest why -- because the populations of adult animals of > sauropod
size are very small, they must have crashed from time to > time, leaving the
young alone. This is a problem for mammals and many > birds, which depend
heavily on their parents.

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So then, they are not advocating sauropod parenting? 

_____________________________


> > Sauropods [...] never dealt with temperatures as extreme as
> > those the leatherback faces.

> The other way round, as HP Randy Irmis has pointed out.

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Okay so then *most* sauropods didn't deal with this type of cold environment.


Better?

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> It is not wise. It just shows that in principle it is possible to > live
with nostrils and lungs 7 m apart. Of course, many sauropods > surpassed this,
and had air-sacs, while the whales have adaptations > to low oxygen supplies.
In the absence of any better analog, it is > the wisest thing available, I'd
say.

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Fair enough


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> > Another on the list has already mentioned rattlesnakes. I'm not > > sure
of their exact migration distance, I only know that Laurence > > Klauber wrote
in his book Rattlesnakes, that they "rarely travel > > over a mile" to reach
their dens, though he also notes that > > "dependable data are not at hand."

> A mile is not comparable to, say, what happens in the Serengeti.

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Yeah, but to be fair, just how many mammals do what wildebeest and zebra do on
the Serengeti?

Besides I did say that this wasn't based on dependable data.

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> > Auffenberg is his 81 study of _V.komodoensis_ states that "adults > > may
move as much as 10km/day..." Now, barring the fact that this is > > yet
another island species I'm using, that is still a pretty hefty > > distance.

> This is becoming more interesting, but it is still much less than 2 > -- 5
km/h...

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I'm not sure I followed your statement here. Care to elaborate?

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> > Crocs are no to migrate long distances over land to find new       > >
waterholes, though it isn't as regular as the other examples.

> How far?

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HP Adam Britton has covered this pretty well; all I can add is that marsh
crocs (_C.palustris_) are supposedly notorious for overland travel between
water holes.

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> > Auffenberg clocks normal walking Komodo monitor speed to be 4.8    > >
km/hr,which easily falls within the range of the dinosaurs and     > >
pachyderms mentioned.

> For how long can a Komodo monitor walk? An hour? :-/

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Unsure; oras probably don't make very good test subjects for treadmill runs,
so I wouldn't be surprised if no such endurance study was done on them.

Auffenberg does mention chasing an ora on a motorcycle for .5 km. But, the
animals was doing 14 km/hr at the time.

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> > How much do we know about _Megalania_?

> I don't know. All I know is that not much is known...

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I love certainty :)

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> > Again, this is a species specific issue.

> Sure?

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Absolutley; it can even be different for each individual. This is the down
side to studying bradymetabolic animals.

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> > I disagree; while it might not be viable to use captive growth > > rates
to normal wild ones, it does show that growth is highly > > dependent on
available food in many reptiles (tortoises might be > > exceptions).

> The implication is that such lots of food aren't available in the > wild,
and never were, so bradymetabolic dinos couldn't have grown big > enough.

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I don't know about that. With many dinosaurs being herbivorous, food lack
would seem unlikely. As for the carnivores, Auffenberg himself, mentions that
ambush predators seem to grow to very large sizes. This could explain the
large theropods (along with the fact that they would have to grow to these
sizes in order to compensate for the herbivores).

As for wild growth rates, Burmese pythons do grow from 22" to 6ft in a year's
time. Varanid breeder Frank Retes (REPTILES, May 99) states that , not only
will all monitors (at least most monitors) mature in under a year's time if
given the right environment, but 4 and 5 month old adult individuals (he
mostly handles small monitors) that he raises are equivalent to the ones that
he finds in the wild of the same age (though wild ones tend to be more
emaciated). 

Environment does matter.

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> I'd rather say that fossil terrestrial crurotarsans were more like >
monitors, that is, "good reptiles" with a hepatic-piston pump > (whereas
monitors have a gular pump), but still rather bradymetabolic > and
slow-growing. The thermophysiology of rauisuchians (vertical > limbs!) is
going to be very interesting once it is studied at all...

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I'll second that :)

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> > Great, now as long as the prey item doesn't make any sharp turns   > >
_T.rex_ will be set ;)

> I don't understand this...

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Just making a jab at the pursuit hunting _T.rex_ hypothesis. Biomechanical
studies on large theropods seem to indicate that they couldn't make sharp
turns. This would be a problem for a pursuit hunter if the prey keeps zigging
and zagging. Now if one was an ambush hunter...

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> > Much of which I can certainly agree with; I just don't see why you > >
need to shove them into the inefficient realm of tachymetabolism to > >
achieve this.

> Hm. Considering that tachymetabolism has not been selected against in >
birds, mammals, and others, it must have some advantage...

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That tachymetabolism is only found in birds and mammals seems telling to me
too. Perhaps once one goes forward they cannot go back.

Does anyone know if naked mole rats have truly dumped their L.C. endothermy?

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> > Komodo dragons were once (and still are) considered to only be     > >
scavengers,

> "And still are"? Even though they're on TV every month?

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What can I say; people like big lizards :)

Seriously though, take a trip to a zoo (preferably a tour) that has them and,
depending on the zoo you could wind up hearing that. I also see it in books
from time to time. For the most part it seems to be disappearing (finally). 

Now if only we could get rid of that erroneous belief that they mainly kill
with their septic bites.

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> [...] they had a hunting activity
> (i.e. predator/prey ratio) that was equal to tigers.

1. Is this the same, hunting activity and predator/prey ratio?

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Same as Bakkers; (i.e. food intake/prey requirements) then yes.

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2. From TV observations (not field observations, though...) I claim their
predator/prey ration is much higher than that of tigers. There are just lots
of them.

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From: Behavioral Ecology of the Komodo Monitor.

Though there is great disparity in comparing the values for oras and the large
mammalian predators, when the latter are considered in terms of the
porportionate difference in predator size and waste percentage of prey, the
disparity is not nearly as great. Thus, though the size ratio of an adult ora
to an adult tiger is 1:3, the ratio of the pounds of ungulate prey required
per year for each is 1:19. When percentage waste is considered it is 1:15 and
when poportionate predator size is considered it is 1:5.

As I said...

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> > Not bad for a damned good reptile :)

Jura


Jurassosaurus's Reptipage: A page devoted to the study of and education on,
the reptilia:

http://reptilis.net

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