more on the Kamikaze ichthyosaur...
From Achim Reisdorf

Before August 2005, I had never heard of "AiG Magazine" or "Creation Magazine". In August 2005, I was surprised to see the article in the online edition of AiG. I had received the information via e-mail from Australia (I was not at all personally informed by AiG Magazine or Creation Magazine of this or any upcoming article).

I was interested to see what Tas Walker & Carl Wieland (2005) considered an `extract' of an article that originally covered ten pages in Factum, including the interview. It is surprising how much statements and citations from the original article can be changed by the views, polemics and the supposed expert knowledge of these authors.

In my view, the article published in Factum (Höneisen 2004) is fair in its description of the distinctly different positions of creationism and my own view of this fossil.

I am even satisfied with the presented interview that was actually based on my e-mail correspondence with Rolf Höneisen, the author of the article.

I guess that the authors of AiG who wrote "It is fascinating to watch him wrestle with the evidence, while trying to hold that the sediments were deposited over a million years" hadn't actually read the interview and the original Factum article, since some of the questions posed in the AiG article had already been answered there.

he peculiar question "How could the rib cage remain flexible, allowing the lungs to collapse, and the snout remain rigid, allowing it to push so far into the sediment?" is certainly neither from the interview nor the Factum article.

At least this question allows us to estimate how detailed the knowledge of authors concerning marine biology (anatomy, physiology etc.), paleontology and taphonomy actually is.

It is of further note that, as he himself has written, Rolf Höneisen (author of the orginal article, and editor-in-chief of Factum Magazine) only partly shares the opinions presented by Tas Walker and Carl Wieland (authors of the AiG/Creation article).

Indeed, most of the points and lines of reasoning in the AiG/Creation article, which were purportedly taken from Factum, were completely misrepresented in such a way as to twist their entire meaning. Also, the additional statements made in the AiG/Creation article and the so-called 'facts' presented, are completely wrong.

At one point, for instance, the AiG article asks: "Curiously, the layers span an`age' of about one million years, and that presents something of a problem for long-age geologists. How could anyone conceive of an ichthyosaur head being buried in a vertical position slowly over a million years, yet remaining preserved along its whole length?"

The Factum article (p. 29), however, states the following: "Er kam zum Schluss, dass jenes Sediment, in das sich der Ichthyosaurier zuerst senkte, "Zwischen wenigen und einer Million Jahre" gebildet worden sein kann. (He came to the conclusion that the sediment into which the ichthyosaur sank can have only been formed over a period of "between just a few years and one million years".)

This statement is correct. That is what we can say from the pure record of index fossils in the section (see the section from Unter Hauenstein), if we solely go by these index fossils and a geological time scale. This is, in fact, discussed in Wetzel & Reisdorf (in press).

The incomplete quotation of AiG/Creation Magazine is of course perhaps due to a translation error (the quote was, however, changed quite substantially!), but the figure ("The evolutionary explanation") in the box, is clearly a manipulation of my original text figure, as printed in the Factum article (page 27). [see here]It is of course completely unacceptable that no note has been made of the modification, and that the result has been portrayed as my own opinion.

For instance, a sediment layer is included in the center of the figure by the AiG, which does NOT exist in the original illustration! The AiG-illustration demonstrates that the ichthyosaur immediately penetrated three layers when it sank into the sediment. This is most definitely not my explanation for the ichthyosaur's imbedding.

In our explanation model (Wetzel & Reisdorf in press) we assume that the ichthyosaur (skull & thorax) was initially embedded in only ONE layer. Before compaction, a concretion started to form around the ichthyosaur parts and led to their excellent preservation. During further burial, the concretion containing the skull experienced differential compaction and moved downward relative to the underlying beds. This concretion penetrated through compacted deposits representing three ammonite zones (this second part of our explanation model was included in the printed Factum article. In the AiG article, this second part is omitted.) Restoring differential compaction, the initial porosity of the sediment can be estimated to have been >70%. Compared to modern analogues, such muds are soft, as ichnofabrics imply (e.g., Hein 1985).

A further comment on the AiG illustration "The facts":

This AiG-illustration of the section does not represent the conditions at the outcrop. You'll find the original illustration in the printed Factum article as fig. 4 (in addition to fig. 3 which represents our knowledge of the small scale outcrop during the excavation campaign in 1999)

The sediment consistency:

A consistency of >70% indicates a very soft sediment. This porosity estimate represents a minimum value, because it does not take into account the effects of pressure solution. Carbonate dissolved by pressure solution is precipitated in nearby pores that can then no longer be affected by further compaction.

his effect leads to an underestimation of the initial porosity when only mechanical compaction is taken into account. Therefore, the initial porosity of the sediment containing the skull might have been higher than calculated for mechanical compaction only. The analysis of the differential compaction provides an indirect estimate of the sediment consistency (via porosity) at the time when the skull was emplaced. This estimate supports the results of the ichnofabric analysis (see Wetzel& Reisdorf in press). As the sediments were soupy-to-soft when the ichthyosaur parts were emplaced, the fins probably prevented further penetration. This is in agreement with findings of Martill (1993) who proposed that a soupy consistency of the substrate is essential for the excellent preservation of articulated organisms in an oxygenated environment.

References
Hein, F.J. (1985): Fine-grained slope and basin deposits, California continental borderland: facies, depositional mechanisms and geotechnical properties: Marine Geology, v. 67, p. 237-262.
Höneisen, R. (2004): Den Kopf im Fels. - Factum, 24. Jg., Nr. 3, p. 25-24; Berneck.
Maisch, M.W. & Reisdorf, A.G. (in press) Evidence for the longest stratigraphic range of a post-Triassic Ichthyosaur: a Leptonectes tenuirostris from the Pliensbachian (Lower Jurassic) of Switzerland. - Geobios.
Martill, D.M. (1993): Soupy substrates: a medium for the exceptional preservation of ichthyosaurs of the Posidonia Shale (Lower Jurassic) of Germany. - Kaupia, Darmstädter Beiträge zur Naturgeschichte, v. 2, p. 77-97.
Walker, T. & Wieland, C. (2005): Long-age thinking dealt a lethal body blow: Kamikaze Ichthyosaur? - Creation, Vol. 27, No. 4, September-November 2005, p. 10-12; Acacia Ridge DC (Autralia).
Wetzel, A. & Reisdorf, A.G. (in press): Ichnofabrics elucidate the accumulation history of a condensed interval containing a vertically emplaced ichthyosaur skull. - In: Bromley et al. (eds): Ichnology at the Crossroads: A Multidimensional Approach to the Science of Organism-Substrate Interactions. - SEPM Spec. Publ.

Achim Reisdorf
University of Basel