Aetogate: Martz's response to Spencer Lucas

Mon Mar 10 14:11:19 GMT 2008


The online version of our rebuttal, and the full discussion of the rebuttal and our criticism of the DCA decision, is still in the works. Bill should have his side of his rebuttal of the "Desmatosuchus" chamaensis case up sometime today or tomorrow. In a nutshell, here is my response to Lucas' discussion of the Redondasuchus case.

Just to briefly recap, everyone now agrees that the holotype of Redondasuchus is a right osteoderm, which puts the flexing (or "arching") closer to the medial edge. This is the interpretation I gave in 2002, and what Spielmann et al "Independantly" came up with in 2006. This basic morphology is typical for posterior dorsal and caudal scutes in many aetosaurs, including Typothorax, which is why I interpreted it this way; interestingly, Spilemann et al. don't give a reason for thier re-interpretation. The older interpretation given by Hunt and Lucas (1991), Heckert et al. (1996), and Heckert and Lucas (2000) is that it was a left, with the flexing being closer to the lateral edge. This gives the scute a "downturned" lateral edge, which they interpreted as being characteristic of the how the scute is oriented has real taxonomic relevance.

Lucas tries to claim credit for the correct reinterpretation of the Redondasuchus holotype in two ways:

1) He says Spielmann figured out the new interpretation "independantly" in 2006, and told Hunt, Heckert, and Lucas, who were "easily convinced." I don't doubt it, since I had sent all three of them copies of my thesis in 2003. It is hard to see how they can even claim partial credit for an intepretaton I had GIVEN them three years earlier. They cited part of my thesis discussing Typothorax ontogeny in a paper in thier "2002" bulletin (actually published in 2003), and the section of my thesis dealing with Redondasuchus extensively in the 2006 bulletin paper (though only on stuff they disagreed with), so they have clearly established they had the copies I gave them.

2) Lucas tries to make out that Heckert et al rrect interpretation. However, the 1996 paper explicitly says it is a left every single time, and, as already noted, bases its diagnosis and discussion of the taxon entirely on the incorrect interpretation (with the flexing closer to the lateral edge). Lucas says if you squint your eyes and read carefully between the lines, they actually mean exactly the opposite. This is not a compelling argument.

Also, all authors on the 1991, 1996, and 2000 papers (Hunt, Heckert, Lucas) were co-authors on the 2006 paper, which says EXPLICITLY that the older papers used the INCORRECT interpretation, fail to mention that Martz gave the correction in 2002, and then present it as a brand new interpretation they came up with themsleves (see quote below). I have a hard time believing anyone who has actually read the papers could fall for Lucas' revisionist history.

Additional points...

3) Lucas and Spielmann et al. (2006) don't seem to understand the significance of the anterior bar to the interpretation. Lucas says that if Heckert et al. recognized the anterior bar, they must have known which end was medial and which was lateral. This is false. Interpreted as a left, and oriented with the flexing closer to the lateral edge (as all the pre-2000 papers did), the anterior bar of the holotype scute still faces forward as it should. Oddly, Spielmann et al. (2006, fig. 1, top left side) figure alleging to show the incorrect, older interpretation shows it as a left, with the flexing CORRECTLY closer to the medial edge; however, this puts the anterior bar along the posterior edge, which is still incorrect (and if anything, even more backwards than the original interpretation).

4) Lucas claims that the Spielmann et al. (2006) Fig. 1 was based on Heckert et al.'s (1996) Fig. 5 and not on Martz's (2002) Fig. 3.1c. Yes and no. The left side of the Spilemann et al. (2006) fig, showing the incorrect interpretation in cross section, is from Heckert et al.'s (1996) figure. The modified version of this figure on the right side is clearly showing the same interpretation as in Martz (2002) Fig. 3.1c. We never claimed that the Spielmann et al figure was reproduced directly from my thesis, only that it is clearly showing the same interpretation. This is important as Spilemann et al at one point cite a different part of Fig. 3.1, so there is no way they could have missed this.

5) Lucas notes that as they cite my thesis extensively in the 2006 paper, they clearly intended to give me credit. As we have already repeatedly pointed out, they only cite me where they disagree with me, on matters having to do with terminology and taxonomy which are not relevant to this debate. They are clearly taking sole credit for the CORRECT reinterpretation of the holotype scute:

"The interpretation of the orientation of flexure in the diagnosis of the genus Redondasuchus presented here (Fig. 1) differs from that of previous studies (Hunt and Lucas, 1991; Heckert et al., 1996). These studies suggested that, for the mid-dorsal paramedian scutes, the point of flexure was “two-thirds of the lateral distance from the medial to lateral edge of the scute” (Heckert et al., 1996, p. 620). However, WE BELEIVE that this is incorrect and that the point of flexure instead lies one-third of the lateral distance from the medial to lateral edge of the scute (Fig. 1). This changes the conception of how the scutes are flexed; previous interpretations had the point of flexure between the medial two-thirds of the scute and the lateral third, while OUR INTERPRETATION has the point of flexure between the medial third of the scute and the lateral two-thirds." (Spielmann et al., 2006, p. 583; BOLDFACE added by me)

6) Last point we just noticed recently. In thier 2007 paper revising the Late Triassic land vertebrate faunachrons, Lucas et al. say that I had claimed the "flexing" in Redondasuchus was due to POST-MORTEM DISTORTION...and that the flexing was correctly identified as natural, and oriented correctly guessed it...Spilemann et al. (2006). It just doesn't stop.

The 2007 paper crediting me with post-mortem distortion is:

Lucas, S.G., Hunt, A.P., Heckert, A.B., and Spielmann, J.A. 2007b. Global Triassic tetrapod biostratigraphy and biochronology: 2007 status. In S.G. Lucas and J.A. Spielmann (eds.) The Global Triassic. New Mexico Museum of Natural History and Science Bulletin 41, pp. 229-240.

The relevant quote is on p. 233, 4th paragraph down on the right column. Nit picky correction of my last post: The 2007 paper doesn't mention that Spielmann et al. (2006) gave the correct orientation, just that they confirmed isn't distorted, and claims that I had said that it WAS distorted.

The fact that Lucas "rebuttal" has gotten the traction it has is a real tribute to his writing and persuasive skills. It also shows that P.T. Barnum knew what he was talking about.