Little red flags for a Saharastega reconstruction

Saharastega moradiensis (Sidor et al., 2005; Late Permian; Fig. 1) is a large, flat-headed, temnospondyl basal tetrapod. According to the original reconstruction (Fig. 1) it is the only temnospondyl in the large reptile tree (LRT, now 962 taxa) in which the jugal has no posterior process and the quadratojugal contacts the postorbital. Those autapomorphies raised red flags that started the present investigation.

Figure 1. Saharastega fossil skull, tracing of fossil skull, freehand reconstruction, all by Sidor et al., followed by color tracing that finds nares at the dorsal rostrum, concave dorsal rostrum and posterior jugal separating the quadratojugal from the postorbital overlooked by Sidor et al.

Figure 1. Saharastega fossil skull, tracing of fossil skull, freehand reconstruction, all by Sidor et al., followed by color tracing that finds nares at the concave dorsal rostrum and posterior jugal separating the quadratojugal from the postorbital

Taking the Saharastega freehand reconstruction at face value
Saharastega was scored and it nested with the coeval Nigerpeton (Fig. 2) which has dorsal nares and anterior fang holes along with a concave rostral profile. These are traits not shared by Saharastega according to the freehand reconstruction (Fig. 1).

Going back to the fossil
and colorizing the bones of Saharastega reveals a skull more like that of Nigerpeton than the freehand reconstruction indicates. It looks like the anterior nares of Saharastega may be fang holes, as in Nigerpeton. Both share dorsal nares and a concave rostral profile, together with a jugal that separates the quadratojugal from the postorbital. Note the placement of the internal nares relative to the external nares in Nigerpeton (Fig. 2). That pattern is more or less shared by Saharastega (Fig. 1).

Figure 2. Nigerpeton nests with its contemporary, Saharastega (figure 1) and has dorsal nares and a concave rostrum.

Figure 2. Nigerpeton nests with its contemporary, Saharastega (figure 1) and has dorsal nares and a concave rostrum.

The two taxa, Nigerpeton and Saharastega,
are not congeneric, but they do appear to share more traits than the authors originally indicated. The crack across the rostrum in Saharastega somewhat obliterated the nares. Otherwise they would have not been overlooked.

References
Sidor CA, O’Keefe FR, Damiani R, Steyer JS, Smith RMH, Larsson HCE, Sereno PC, Ide O and Maga A 2005. Permian tetrapods from the Sahara show climate-controlled endemism in Pangaea. Nature. 434 (7035): 886–889. doi:10.1038/nature03393. PMID 15829962.
Damiani R, Sidor CA, Steyer JS. Smith RMH, Larsson HCE, Maga A and Ide O 2006. The vertebrate fauna of the Upper Permian of Niger. V. The primitive temnospondyl Saharastega moradiensis. Journal of Vertebrate Paleontology. 26 (3): 559–572. doi:
wiki/Saharastega

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One thought on “Little red flags for a Saharastega reconstruction

  1. In November I went to Seattle and spent three days with all material of Saharastega and Nigerpeton known to science, including the more or less unpublished fragments.

    First, let me say that trying to trace sutures is hopeless for much of the entire skull of both. The surfaces that aren’t eroded and crisscrossed by fractures are covered with a very hard crust (much like Texas Redbeds material), so the sutures on the palate and on the unpublished lower jaw are pure guesswork. Trying to prepare the crust out from between the denticles that cover the palate and much of the lower jaw would take ages. I hope someone will CT-scan the stuff; depending on what the crust consists of, a neutron scan may well be necessary.

    Second, why on Earth do you try to do DGS on the interpretative drawings of Saharastega? Anything that Damiani et al. didn’t see is not in the drawing, because you can only draw what you see!

    Third, the nostrils of Saharastega are not where you think they are. (That’s just damage, I’ve seen it from both sides. It’s a pretty ridiculous place, too, at the caudal end of the choanae. I mean, come on. This isn’t some kind of plesiosaur.) Quite possibly they aren’t where Sidor et al. thought they are either; that area, too, is damaged to such an extent the large ovals in the reconstruction are guesswork. On one side I’ve found something that could be a colosteid-style tiny, ventrally-facing nostril, but that area, too, is too damaged to tell for sure; on the other side the whole area is missing. I talked to Chris Sidor about it, and he basically was like “anything is possible”. I have photos and may (or may not) end up publishing on this; we’ll see…

    Fourth: again: the material is really close to hopeless. The published black-&-white photos are hopeless, the published drawings are educated guesses, and the specimens themselves are nearly hopeless, too.

    On Nigerpeton, make sure you see the 2013 paper on the new specimen, a snout tip that is not horribly eroded. There you can see that the holes for the tusks of the lower jaw don’t exist, or at least don’t pierce the snout roof, at least not in that specimen. The specimen the reconstruction drawing of –

    Oh. You missed the 2006 JVP paper on Nigerpeton, too. There’s a free pdf of it out there; just look it up on Google Scholar. Why do you bother writing a blog post when you’ve only seen half of the relevant literature?

    – so, the reconstruction drawing in the Nature paper of 2005 and the JVP paper of 2006 is based on the holotype, which is so eroded that what you can see on the dorsal side isn’t the roof of the snout, it’s the dorsal side of the palate. The idea that the holes in the palate would continue through the snout roof, as they do in Mastodonsaurus, was just an educated guess. Quite possibly there was individual variation, but the one snout roof we have is closed except of course for the nostrils.

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