Friday, July 06, 2007
More about the "Death Pose"
Last year, Ian Juby gave us the low-down on the "death pose" (for more info on Ian and his travelling Creation museum, see ianjuby.org) - the position that dinosaurs are often found in. Here are some of Ian's comments about it:
The first thing you are met with is an in-situ dinosaur cast showing the "death pose" that I have been studying for the past year or so...For those not familiar with this, long necked, articulated animals in the fossil record commonly have their heads arched back as far as they can possibly go...the conventional thinking is that they laid out and dried up, the tendons on the back of the neck shriveled as it dried up, thus pulling the head back.
I have claimed that the heads are arched back due to suffocation: The last thing to go underwater when drowning is the head. Furthermore, while some of the animals exhibiting this death pose have their mouths open, others do not. In either case, even humans that are suffocating arch their heads back. I used to have asthma, that's how I know.
What I'm suggesting is that they were buried alive, and the stress of this event is exhibited in their taphonomy in burial. [NOTE - Ian is indicating that the burial event is the flood and their posture testifies to it]
At the Tyrell they had Archaeopteryx, compsagnathus, and at least EIGHT dinosaurs all exhibiting the death pose. Of those, NONE had tensed legs or arms. Some have the tails arched back as well, which could also be a reaction to being buried alive, or Joe Taylor also suggested defication.
Well, in the most recent issue of Paleobiology, we have additional support for Ian's interpretation of the "Death Pose" in a paper titled The opisthotonic posture of vertebrate skeletons: postmortem contraction or death throws? [NOTE - the "opisthotonic posture" is the "death pose"]
The paper argues:
- Conventional post-mortem paleontological explanations for this position has no experimental evidence.
- We have a lot of evidence in the clinical literature of why this happens before death
- Taphonomic evidence argues against any long-period interpretation of this position because carcasses quickly become stuck to the beach in dry conditions and cannot be moved even by severe flooding.
- Opisthotonic postures must have been buried quickly after drowning and then been left undisturbed.
- Rigor mortis creates muscle stiffness, not contraction, so it cannot be an explanation of the position, though it can preserve the position after death for a short period if the animal was in that position at the time of death.
- A carcass carried in water flow can sometimes cause a similar position to appear, though these are often disarticulated, and they are with the current flow.
The authors described numerous taphonomic experiments (i.e. watching what happens when/after animals die in various conditions) of animals that had been euthanized at a local humane society that validated that none of the post-mortem hypotheses for the posture stands up to experimental scrutiny.
The available evidence shows that, instead of being a postmortem artifact, the true opisthotonic posture is a consequence of the spasmodic response of the animal's CNS [central nervous system] and musculoskeletal systems to hypoxia (lack of oxygen) and other CNS diseases experienced in the final moments of life. The subsequent onset of rigor mortis would (temporarily) fix the carcass in this position, if it is not previously disturbed, and burial would provide ultimate preservation. So it could be concluded that, in general, vertebrate skeletons preserved in the opisthotonic position were buried soon after death, generally without substantial transport, and did not suffer extensive deterioration from currents or scavengers.
They also point out that the opisthotonic position is correlated with "high basal metabolic rates" (i.e. warm-bloodedness), which I assume they are saying indirectly that dinosaurs may have been warm-blooded, though they hold that more tentatively.
And, for your pleasure, here are most of Ian Juby's "death pose" pictures (he's working on descriptions for these and we will post the page when he has it done):
I don't think that's nearly as relevant, and here's why -- the "death pose" only occurs in those who were drowned _and_ immediately buried. If it was carried in water for over a period of time before depostion (I think it was 3 hours, but I could be wrong) then it would not have the "death pose". So it's not surprising that some animals dying in the flood would not be in the position, but it would be surprising to have so many in that position were there not a catastrophic even such as the flood which can account for such drowning and rapid burial on a global scale.
That being said, I'm sure there were dinos that survived the flood. So that indeed could also account for it.