Male and Female Stegosaurus?

Usually I leave dinosaurs to the dinosaur experts…
but this new paper seems to be appropriate fodder.

Figure 1. Click to enlarge. According to Saitta 2015, male and female Stegosaurus can be differentiated by their plates.

Figure 1. Click to enlarge. According to Saitta 2015, male and female Stegosaurus can be differentiated by their plates.

 

A recent PlosOne paper by Saitta (2015) claims Stegosaurus sexual dimorphism can be determined by plate shape (Fig. 1).

Unfortunately others disagree.
Drs. Kevin Padian and Ken Carpenter raised serious issues here.

And part of the problem,
perhaps a major part of the problem, is the lack of articulation in the specimens (Fig. 2).

Figure 2. An insitu plot of the Stegosaurus material. Deep blue colors indicate plates, provided by Saitta. Three pelves of different shapes and sizes are marked. Arrows point anteriorly. This is a jumble. And the plates are disarticulated.

Figure 2. An insitu plot of the Stegosaurus material. Deep blue colors indicate plates, provided by Saitta. Three pelves of different shapes and sizes are marked. Arrows point anteriorly. This is a jumble. And the plates are disarticulated.

A plot
of the in situ specimens (Fig. 2)  indicates that at least three individuals are shown in disarray here, (five were mentioned and likely the others are from other parts of the site). One is smaller than the others. How is it possible to match plates to pelves? And how do all the other bones fit herel? I would not want to attempt a reconstruction with this scattering of at least three individuals.

This is a hard hypothesis to substantiate. 
Not only do different stegosaurs have different shaped plates, but nearly every plate on every stegosaur is distinct, even in articulated specimens.

What I find most interesting…
How did Drs. Padian and Carpenter get their comments published online at ScienceMag.org on the same day the PlosOne paper came online? Only Carpenter is listed in the acknowledgments (for providing specimen photos). Both are listed in the references.  I assume they were not referees, but must have been granted access to the paper prior to publication.

And, why are their no comments in the COMMENTS section for this paper (at the time of this publication)? That’s the standard operating procedure for PlosOne papers.

References
Saitta ET 2015. Evidence for Sexual Dimorphism in the Plated Dinosaur Stegosaurus mjosi (Ornithischia, Stegosauria) from the Morrison Formation (Upper Jurassic) of Western USA. PLoS ONE 10(4): e0123503. doi:10.1371/journal.pone.0123503

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