Breaking Bone-Head News!

Recently, your HMNS curator of paleontology, Dr. Bob, along with some friends, announced a new bone-head dinosaur, a family with the technical name “pachycephalosaurid,” meaning “thick-headed reptile,” or “pachy” for short.

Our new pachy was based on a complete skull and some neck bones found by talented and dedicated amateurs and donated to the Indianapolis Childrens Museum. Since the new beast looked like a medieval dragon, we named the genus Dracorex, meaning “Dragon King.”

Most exciting was the fact that the skull came with several neck bones. Neck bones from pachys are very rare and the butting abilities of these dinos has been hotly debated. The Dracorex neck  had special anti-twist joints that would let the critter butt, shove and bang heads.

dracorexcolor
 Two Dracorexes butt heads
to score points in the mating game

We named the species in honor of J. K. Rowling’s magical academy, Hogwarts. So the full names is: Dracorex hogwartsia.  Has a nice ring, doesn’t it?

dracorex-portrait
Dracorex hogwartsia at the
Indianapolis Childrens Museum

The new bone-head  dinosaur was way different from any other bone-headed dinosaur discovered so far. Unlike Pachycephalosaurus, Stegoceras and their kin, Dracorex had no dome of bone in the middle of the forehead but had, instead, all sorts of knobs surrounding two huge holes. Unlike Stygimoloch, another famous bone-head, Dracorex had big holes and horns that were shorter.

Another difference – so we thought – were the upper nipper teeth, the incisors in the premaxillary bone. Dracorex didn’t have any. Most other bone-heads did.

Well……we were wrong.

True, the Dracorex skull as preserved had no upper nipper teeth and no sockets for such teeth either. This condition wasn’t necessarily a surprise. Many advanced plant-eaters lose their upper nippers. Cows and antelope have no upper incisors. Instead they have a tough pad in the roof of the mouth – the lower nippers bite into the pad when the critter tears off a tuft of grass.

Therefore we concluded that our bone-head was doing the cow-thing in its snout.

But Victor Porter, head of the lab at the Indianapolis Museum, had cleaned a peculiar tooth found with the skull. It was bigger than the back teeth, more triangular, and didn’t show wear from lower teeth.

drakoin8brite
 Upper nipper of Dracorex hogwartsia
dragonhed3
Snout of Dracorex hogwartsia
with upper incisors restored

Our colleague and friend Mike Triebold of the Dinosaur Resource Center showed other new skulls – and they had just this type of teeth in the snout tip. (Mike has the most important pachy collection in the country). There’s no doubt: Dracorex hogwartsia  had big upper incisors too.  Our bone-head must have used its formidable nippers to bite off bits of vegetation – and to bite other Dracorexes when the dinos got frisky.

Why didn’t the Indianapolis skull preserve the holes for the deep roots of the nippers? The sockets must have been huge, since the root on the tooth was very long. We don’t know.  After death, something or someone broke the bone along the front of the mouth, destroying the sockets and loosening all the front teeth.

In paleontology, there always surprises…..more on Butt-Heads again soon.    

5 thoughts on “Breaking Bone-Head News!

  1. Bob,

    I was watching a science channel show about mass extinctions where you said you didn’t believe in an collision caused extinction .

    One of the reasons you gave was that there would be fossils lying everywhere. This is really a statistically unsound statement.

    I make two assumptions, neither of which needs to be anywhere close to reality, but which allow me to plug in “some” numbers.

    1. The average age of a dinosaur that turned into a fossil was 10 years old.

    2. There were about an equal number of dinosaurs alive on earth at any time during the age of dinosaurs.

    If the average age of a dinosaur was ten when it hit the ground, then the number of dinosaurs that died during a ten year period would be the same as the number alive at any given time or the number that would hit the ground during a single event extinction.

    Since there were about 16 million ten year periods in the total age of dinosaurs, that means that the total number of fossils that have been collected to date, which come from the entire 160 million year period, is about 16 million times the number you would expect to find in any given ten year period or from a single event extinction.

    This means that the fossil record of a single event extinction would be virtually undetectable.

    I’m looking forward to your ”Dinosaur Heresies” update.

    Ralph Wilhelm

  2. @ Raptor Lewis:

    Yes, it does. What you beleive has, frankly, no bearing on anything scientific, not when it is not based on facts (or is based on bogus “facts”, of the kind in Horner and Goodwin’s recent paper on this issue). Bakker is currently studying a genuine baby Pachycephalosaurus. This baby looks nothing like Dracorex, but is just as small. The dome is fully developed, there are knobs at the back of the head rather than horns, and the temporal fenestrae are gone. Now that we have a baby Pachy that looks just like an adult Pachy, and nothing like a Dracorex, this matter should not even be open for debate.

  3. In regards to my old comment above, it does not represent my current viewpoints. Until Dr. Bakker actually publishes on his pachycephalosaur material, I am of the opinion that the model Horner and Goodwin (2009) proposed is by far the most parsimonious interpretation of the currently available data. In short, I was wrong, Horner and Goodwin are (most likely) right, and Dracorex and Stygimoloch are (most likely) juvenile Pachycephalosaurus.

  4. @ Michael O. Erickson

    As indicated by the following quote, he already has. This isn’t the 1st time Horner’s ignored contradictory evidence.

    Quoting Bakker et al. (See “DISCUSSION”: http://uuu.childrensmuseum.org/themuseum/dinosphere/draco_rex/dracorex_hogwartsia.pdf ): Dracorex hogwartsia is most similar to Stygimoloch spiniferand toa lesser extent Pachycephalosaurus wyomingensis. It is considered to be amember of the Pachycephalosaurini as defined by Sullivan (2003). How-ever, it is readily distinguishable from these two taxa based on a number ofkey features. Stygimoloch spinifer is characterized by a huge spike cluster,consisting of 3 enlarged (hypertrophied) spikes. This differs from the shorter4 spike arrangement in Dracorex hogwartsia. Galton and Sues (1983)characterized Stygimoloch spinifer as having three-to-four spikes on thesquamosal. This characterization allowed them to include a smaller, iso-lated squamosal with four spikes (YPM 335), a specimen we here con-sider to be referable to Dracorex hogwartsia. We have been able to deter-mine, based on comparison with other documented specimens ofStygimoloch spinifer (MPM 7111 and MPM 8111), and two undescribedspecimens in private collections, that S. spinifer consistently has these en-larged spikes coupled with an incipient, laterally compressed dome, madeup of only the frontals and parietal. S. spinifer lacks open supratemporalfenestrae. Moreover, these skulls are of the same size as the holotype ofDracorex hogwartsia, so we conclude that these differences are not theresult of ontogenetic development.

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