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Tuesday, October 21, 2014

Arched Necks In Dinosaur Fossils: Is Water to Blame?

Posted by jlwile on February 28, 2012

The position of the head and neck in this fossil is common among dinosaur fossils (Click for credt).

Relatively complete dinosaur fossils are fairly rare. Additionally, fossils in which the bones are essentially preserved in their proper arrangement (called fully articulated fossils) are even more rare. However, among these rare, fully-articulated fossils, there is a common feature: the head is often thrown back, curving the neck, as shown in the fossil on the left. This is so common it has its own scientific term. It is called the opisthotonic posture. Since it is so common among dinosaur fossils, it has been recognized for a long time. Indeed, the first reference to it in the scientific literature can be traced to a German paper that was written by A. Wagner back in 1859.1 Since then, paleontologists have been trying to figure out what causes this unusual “death pose.”


This investigation has produced a lot of speculation, but in the end, a study that was published in 2007 seemed to have settled the issue. It was done by a veterinarian, Dr. Cynthia Marshall Faux, and a vertebrate paleontologist, Dr. Kevin Padian. That seems like a perfect team when it comes to figuring out what’s going on here. The veterinarian would understand the various physiological and anatomical features of living vertebrates and how they would change during the death process, and the paleontologist would understand the details regarding the fossilization process. Their conclusion was:2

It is not postmortem contraction but perimortem muscle spasms resulting from various afflictions of the central nervous system that cause these extreme postures.

So according to Faux and Padian, the opisthotonic posture occurs at or near the time of death (perimortem) due to problems related to the central nervous system. It has nothing to do with what happens after death (postmortem). Their study got a lot of press and was considered by some to be the final say on the matter.

That is, until last year.

In November of 2011, Alicia Cutler reported on the results of experiments in which she used dead chickens to study the effects of various postmortem conditions on the posture of the skeletal remains. She found that when dead chickens were laid out in sand, nothing really happened to the posture of their skeletons. However, when the dead chickens were immersed in fresh water, they went into the opisthotonic posture in a matter of seconds. This indicates that the death pose of fossil dinosaurs might be the result of postmortem water exposure. I saw the news story I linked above not long after it came out, but I decided not to write about it, since the results were presented at a meeting. I generally like to have a paper to read before I comment on studies that have been done.

Well, as far as I can tell, Cutler has not written a paper about her results, but sedimentologist Dr. Achim Reisdorf and palaeontologist Dr. Michael Wuttke have. They wrote a detailed paper reviewing all the work that has gone on related to this issue as well as their own experiments and investigations. They come to a conclusion that is very similar to Cutler’s.

In their paper, they examine two very well-preserved fossils that exhibited the opisthotonic posture and decide that what they see cannot be reconciled with the conclusions of Faux and Padian. However, such analysis contains a lot of speculation, to which the authors freely admit. To me, the more convincing aspect of their study is that they performed experiments similar to, but more detailed than, the ones done by Cutler, while still giving Cutler credit for her work. They confirm that when dead chickens are placed in water, they quickly attain the opisthotonic posture, and they even demonstrate the anatomical details as to why this happens. They also confirm that those same anatomical details are found in the dinosaurs that are typically found in the opisthotonic posture.

In the end, they conclude:3

From what has been presented above, it can be concluded that the formation of the “opisthotonic posture” in subaquatically deposited carcasses of long-necked and longtailed reptiles is the result of a postmortem process…this posture must be seen as a normal phenomenon that occurs during subaquatic gradual embedding of these sorts of carcasses.

In other words, right now, the fact that so many articulated dinosaur fossils are found in the opisthotonic posture is probably related to specific postmortem changes that occur as a result of being buried in watery sediment. Of course, that fits in perfectly with the idea that these dinosaur fossils are the result of the actions of a worldwide Flood.

REFERENCES

1. Wagner A, “Über einige, im lithographischen Schiefer neu aufgefundene Schildkröten und Saurier,” Gelehrte Anz königl Bayer Akad Wiss 69:1-69, 1859.
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2. Faux CM, Padian K, “The opisthotonic posture of vertebrate skeletons: post-mortem contraction or death throes?,” Paleobiolology 33:201–226, 2007.
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3. Achim G. Reisdorf and Michael Wuttke, “Re-evaluating Moodie’s Opisthotonic-Posture Hypothesis in Fossil Vertebrates Part I: Reptiles—the taphonomy of the bipedal dinosaurs Compsognathus longipes and Juravenator starki from the Solnhofen Archipelago (Jurassic, Germany),” Palaeobiodiversity and Palaeoenvironments 92:119-168, 2012.
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Comments

53 Responses to “Arched Necks In Dinosaur Fossils: Is Water to Blame?”
  1. Aimee G says:

    Would someone please send L.W. a thesaurus and a dictionary? If I have to read about “nutters” and “nuttery” or read the phrase “trot out” one more time, I think I will scream. When people can’t think of something else to say, they should stop talking rather than repeating the same gibberish incessantly. “Believing themselves wise….they became fools.”

  2. jlwile says:

    Jason, I appreciate your point of view. Local floods would, indeed, also be consistent with the data. I find that suggestion significantly harder to believe, as it would require a lot of local floods all around the world, and our current experience is that some parts of the world are significantly less likely to experience floods than other parts of the world. I find a global Flood much more reasonable, but there is no way to make that distinction based on these specific data. Please note that I did not concluded that there must have been a global Flood from these data. I simply indicated that these data are quite consistent with a global Flood, which is most certainly true.

  3. jlwile says:

    Aimee, even if someone gave L.W. a thesaurus, it is not clear he would use it. After all, I have given him several resources that would allow him to learn about science, and he has not used them at all. I seriously doubt that he would use a thesaurus!

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