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BAD BREEDING mutated from BAD vs. BAND

Extinction at the end of the cretaceous had to be from a large number of species specific causes from the impactors (or other causational accumulative) effects. I hadn't thought about the temperature thing (TSD) for a while but I am certain that it would have effected some species over the short term. I will add this to my list of effects as a result the initial cause of the end result. A lot of these big animals certainly lived a long time though and probably reproduced over a long span of years. A bad 5 or 10 year stretch of bad breeding conditions may not have had much effect on some while others it would certainly decimate. It didn't appear to bother avian dinosaurs of the time, turtles, alligators and crocs however. Disruption of the food chain, disease, climate change, fires, habitat disruption, acid rain, competition for limited resources and other causes all had an effect on the overall extinction process at the K/ T. There may have been a primary instigating event like an impactor but the cause of each species die off was unique to each variety. Makes sense to me even if it was published in French. :-)
Frank (Rooster) Bliss
MS Biostratigraphy
Weston, Wyoming
www.cattleranch.org


On Aug 30, 2006, at 10:28 PM, John Scanlon wrote:

There've been some remarks from one or several folks disparaging an argument
attributed to one Spotila, suggesting that (A) dinosaurs probably had
temperature-dependent sex determination (TSD), so (B) sudden change in
global temperature (even if only a few degrees, if persisting for long
enough) could be a mechanism for mass-extinction by distorting sex ratio in
a large number of species simultaneously.

I read the paper some while ago, and mainly noticed that the same argument
had been published years earlier by J.C. Rage. But maybe that was in French
so didn't count, I dunno. But the criticism here seems to be that Spotila
argued from dinosaurs being 'reptiles', and 'reptiles' have TSD... QED.

Now I don't recall how the argument was actually phrased, but look at it
this way. Extant dinosaurs (Aves) don't have TSD, but all crocodilians do
(AFAIK); most if not all turtles do (and they may be derived archosaurs, or
at least much sequence evidence suggests so); Sphenodon and many (if not
all) Iguania do. Thus, TSD characterises the three successive outgroups to
Dinosauria: i.e. it is most likely the ancestral state. It's been lost
somewhere on the line to extant Aves, but could well have been present in
all non-avian dinosaurs. Or of course - and I'm not sure if Spotila or even
Rage explicitly noted this - an ancestor of all dinosaurs could have already
switched to GSD; maybe the 'bird vs. reptile' prejudice actually entered
here, but does not effect the rest of the argument.

Cheers,
John

-----------------------------------------------
Dr John D. Scanlon
Palaeontologist,
Riversleigh Fossil Centre, Outback at Isa
19 Marian Street / PO Box 1094
Mount Isa  QLD  4825
AUSTRALIA
Ph:   07 4749 1555
Fax: 07 4743 6296
Email: riversleigh@outbackatisa.com.au
http://tinyurl.com/f2rby


-----Original Message-----
From: dinoboygraphics@aol.com [mailto:dinoboygraphics@aol.com]
Sent: Friday, August 25, 2006 2:11 AM
To: david.marjanovic@gmx.at; dinosaur@usc.edu
Cc: pristichampsus@yahoo.com
Subject: Re: BAD vs. BADD (was: Re: Most popular/common dinosaur
misconceptions)

Long story short, as a disparity guage, the Linnean
rank system tends to work very well.

It tends not to work at all.

Actually, it works much more poorly than "not at all". Not at all
would imply a largely inconsequential hueristic device, but the fact
that it doesn't in any way accurately measure disparity, but causes
people to believe it does makes it misleading, sometimes to an almost
vicsious degree. I am still asked on a regular basis if a pterosaur or
theropod with dermal insulation is still a "reptile". Whether Spotilia
"knew better" or not he still published and then regurgitated for the
popular press an idea that can't even be framed when held to a
phylogenetic framework. Much of the resistance to dino-fuzz covered
coelurosaurs and winged non-avian maniraptorans seems to stem from
Linnean-style typological thinking. The popular idea that the fossil
record doesn't show abundant (and I mean *abundant*) transitional forms
stems from the habbit of lumping them into existing "ranks" (after all,
if Tiktaalik is a fish and Ventastega a tetrapod, there aren't any
intermediate forms...!). The fact that on this very list it was
claimed that inner ear bones (which are likely homoplastic anyways) and
fur makes whales, bats, and pyrotheres all mammals, while running with
slightly less femoral excursion makes extant birds different from
theropods, shows how badly misleading the system is.

As a gauge of disparity, the Linnean system is an absolute disaster.

Scott Hartman
Science Director
Wyoming Dinosaur Center
110 Carter Ranch Rd.
Thermopolis, WY 82443
(800) 455-3466 ext. 230
Cell: (307) 921-8333

www.skeletaldrawing.com


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