Dr. Masiaka, Meet Mr. Vicious


Very short post. The full post will occur on October 31st.

So what was the solution to my “mystery theropod“?

What do YOU think this is?

Here is the first image. Seems innocent enough. But appearances are deceiving. This is Dr. Masiaka, and as one can guess from the title of this post and a very broad reading of Robert Louis Stevenson, the identity of his alter-ego is plain:

Mumsy and DadsyThere’s something interesting about expanding the structure of “lips” in theropods to animals with exaggerated teeth. How, really, does one fit “lips’ around a closing jaw with wicked teeth? I do not think the solution is very difficult, what with enough flesh around the jaw to close over the upper teeth as in lizards. The closed-jaw model was illustrated first, over a designed based on a completed skull reconstruction, which will appear in the next post. This allowed me to model the lip-structure accurately enough following the model I used for Velociraptor mongoliensis here.

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5 Responses to Dr. Masiaka, Meet Mr. Vicious

  1. Except Masiakasaurus has decurved dentary, which you show in the open-mouthed restoration, but not the original close-mouthed one (and since the close-mouthed one doesn’t have a deeper mandible, you can’t blame that on skin extending from the synphysis as a gular pouch or something). Plus, if you have the premaxillary ventral margin level with the maxilla’s as in Cau’s recon (http://theropoda.blogspot.com/2011/01/una-ricostruzione-alternativa-del.html), you get a shorter, triangular snout. If you want to counter the upper snout is too fragmentary to restore a definite outline on, then the only thing your readers could compare was the flawed dentary outline. So I’d say you ignored both the proper upper and lower snout outlines, which are really all we have to work with.

    • The “higher curvature” of the dentary in the “open” illustration must also come from the fact that the jaw is slightly medial and dorsal to the dentition of the upper jaw in adduction, so when the jaw is closed a portion of it is hidden, and the “lips” are depressed below the margin following the pair of jaws: it does not mimic the jaw line. Because I wanted to avoid too many erase lines, I used a base illustration of the skull and jaw and literally traced my outline over it by the same degree in “open” and “closed”; I played with the integument a bit to make sure there was room for everything, allowed some elasticity so that the lower “lip” could flop a little downward while the jaw is depressed, but otherwise the skulls in both are essentially identical. The only real problems between the two was trying to match the squamation between them.

      Understand that with my skull reconstruction, which you haven’t seen, I’ve also revised some options on orientation and placement of the premaxilla relative to the other bones of the skull, a little thing I thew by Matt Carrano at SVP 2003. Certainly interesting following the published reconstruction in 2011, and I admit my reconstruction is as plausible as any other given the absence of material involved, but I do not think my underlying basis for skull shape too wrong. I will be glad to hear your opinion Oct 31, if you’re not too busy by then.

      • I meant the ventral edge of the dentary should be concave in the close-mouthed picture, which the closed mouth should have no effect on. As for your unseen cranial reconstruction being as plausible as any other, I have no reason to doubt it, but then my closing sentences still apply- “If you want to counter the upper snout is too fragmentary to restore a definite outline on, then the only thing your readers could compare was the flawed dentary outline. So I’d say you ignored both the proper upper and lower snout outlines, which are really all we have to work with.”

        • Why would you think the gular margin of the jaw should be concave, any more that it [slightly] is? Part of the problem that pervades scientific reconstruction of dinosaur heads is that, rather unlike mammal illustration from such masters as Anton and Buell and Knight, the dinosaurs get their heads shrink-wrapped. Comparison of these regions in very broad, general perspective to other sauropsidans/reptiles — not just birds — and even mammals suggests that we can approach the soft-tissue more liberally, and that these tissues will often obscure even the dorsal margin of the skull (save where the tissues suggest croc-like approximation of the bony contours, which it doesn’t in this case), gular margin of the jaw, the jaw line itself, the margin of the jaw at the head-neck transition, the fossae in the skull, etc. Sure, there are depressions and such, but we’ve been drawing them as if there are sharp lines with different patterns of integument involved above the antorbital fossa, within the robital fenestra, the laterotemporal, etc.

          I will further discuss the reconstruction and its problems when you’ve had a chance to see it.

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