Freakishly Awesome

No, nothing's wrong with his head. Why'd you ask?Ordinarily, the nasal passage passes through the typical reptilian skull from the external naris into the internal naris, through the choanae. This passage is very short in lepidosaurs, but getting to archosauromorphans, it becomes longer: the choanae move further back in the skull, and the internal naris goes with it. This passage becomes nice and long in some taxa, especially birds, where the internal nares are positioned well back in the throat. This gives them lots of room for internal nasal tissues and expansions of the nasopharyngeal diverticulae of the cranial air sacs.  And boy, do oviraptorids have lots of cranial air sacs.

But, oviraptorids have extremely short snouts. This generally means they end up not being able to use much of this space. So, instead, oviraptorids fold the nasal passage around. Now what is shown above is a “minimum” length nasal passage hypothesis. There is a longer one, and I personally favor this, but I won’t show it yet. But there are several points to be had:

The external, fleshy naris is positioned outside the skull proper, it is not defined by the position of the bony naris. Instead, you locate it largely through the circumnarial fossae around the bony naris. This, then, becomes the nostril. Here, it is shown in carmine red.

The red arrow tracks the passage through the floor of the anterior nasal chamber, which is quite high (those are VERY large bony nares) and extends to the maxillary antrum, which is largely defined by the medial maxillary fenestrae and positioned between the antorbital fenestrae … in typical theropods. In oviraptorids, the antrum extends further posteriorly, so the nasal passage follows suit. This ends up sending the passage down between the eyeballs, but don’t worry: there’s room. The skull is very wide, even if those eyeballs are huge.

The arrow exits the skull into the floor of the palatal vault, at the anterior end (here) of the internal bony naris. Now, the fleshy internal naris is positioned variably within the bony one, but I am tending to orient the arrow further to the rear, so that it passes along between the jugals a bit more, then heads south.

This, then, is how you fit a nasal passage roughly the length of the skull into 1/3 that distance, and while some dinosaurs have this beat by miles, oviraptorids make a better go at it than many theropods. And recall that I am projecting a conservative length here.

So, while oviraptorids have short little schnozes, they have HUGE noses.

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4 Responses to Freakishly Awesome

  1. Interesting take and a great illustration. However, I’m struck by the rather normal premaxilla and rather normal circumorbital area combined with the freakishly short maxillary area in this genus compared to dromaeosaurs, etc. Same observation, different POV.

    • The premaxilla might seem normal in comparison now, but it’s actually rather peculiar, a point I may eventually get into at some point down the road (though I wish the CT data on rostra like this would be more refined). As for the circumorbital region, it is only enough I should say that much of the skull points to the entire preorbital region of oviraptorid skulls having been downturned by as little as 15 or as much as 30 degrees from the “normal” attitude. On top of this, the snout and preorbital region is incredibly shortened. This requires changes to other bones. As I mention here and here, this causes problems in certain types of analysis, likely massively affects oviraptorids in phylogenetic analysis as it obscured phenetic similarities to other groups, while at the same time obscures relatedness signals with other oviraptorids (whish results in problems in resolving oviraptorosaur relationships).

  2. Duane says:

    Long time reader- first time commentator. Its obvious that you take a particular interest in oviraptors. But I have noticed you take a pretty hard, anatomical approach to them- in which the detail you get into is astounding. What I was wondering, and what as far as I can tell you have not put forth, is what you speculate they were eating with those skulls. Again, just like to hear your informed speculations on their diet- I know we don’t have absolute proof…

    • The reason I don’t expound on what I think the diet is is based on my reluctance to eventually shove my foot in my mouth. This question (what did oviraptorids eat?) requires a biomechanical and practical answer, which I am not I think qualified to answer at the moment. I suspect, and have good arguments to support, what the diet could be, but these must be tested. I will, shortly, try to post something more substantive in the near future, but it will take some time. The illustration in this post is, in fact, partly built on that data.

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