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Pachycephalosaurs have always been kind of an enigma. Scientists have never been completely sure just where they fit in the dinosaur family tree (the current consensus is that they are closer to ceratopsians, but I’ve heard other theories). Usually all we know from them are their skulls, and they are some weird looking dinosaurs.
Though I personally think they’re awesome.
The most obvious feature of the skulls of many pachycephalosaurs were their thick, often domed craniums. Scientists and paleo-artists wondered for years about the purpose of this thick skull. One of the most enduring and popular theories is that they were used in combat. But not just any combat; many a paleo-artist reconstructed these dinosaurs head butting like billy goats.
This image has been reproduced so many times that for many people it just became undisputed fact that dinosaurs that pachycephalosaurs did this. I can’t remember reading a children’s dinosaur book that didn’t depict these dinosaurs engaging in such behavior, and few if any didn’t at least mention the behavior.
Not only was this trope very common in popular dinosaur art, but whenever this dino made an appearance in any dinosaur media, expect lots of head butting. Notable examples include this creature’s appearances in The Land Before Time films and The Lost World: Jurassic Park.
In The Lost World Jurassic Park, the Pachycephalosaurus (which is jokingly referred to as Friar Tuck)…
See the resemblance?
…are shown ramming into jeeps. One of the characters, a paleontologist, explains that they were able to this this because the dinosaurs skull attached on the bottom of it’s skull instead of the back of the head like most animals, which is true. This would allow the the body to straighten vertically when his head is lowered and take the force of the impact a lot better than most creatures. This was the most compelling evidence for this type of behavior, and to be honest, it does sound pretty rock solid. However, over recent years, things have gotten a little more complicated.
Despite the thick skull, many scientists theorized that the skull was unfit for ramming. Many illustrations show the dinosaurs going into a running start right before they ram their skulls together, like modern big horned sheep. But with it’s rounded head, it’s been thought that the skulls instead would slide off each other, and that would risk serious injury.
So, if their heads were the wrong shape, did they use it for ramming at all? It would seem so, since many skulls of pachycephalosaurs have been found with cranial lesions, suggesting aggressive behavior.
So, what did they do? Some have suggested that they used their thick skulls to fight off predators, and while this tactic may be of use to troodonts and dromaeosaurs, I doubt it would be very effective against tyrannosaurs as it is sometime seen.
Fighting between others of their kind has still been brought up, but instead of having a running start before ramming heads, one suggestion was that they instead pushed against each other while standing in one place. Another popular theory was that they instead hit each other on their sides, in a display frequently called ‘flanking’.
Depictions of the pushing theory, the popular collision theory, and the flanking theory.
Then again, these theories may just be compromises to keep the ‘fighting dinosaurs’ image of these animals alive. Nature isn’t always so exciting, and some have proposed that the pachycephalosaurs didn’t ram into each other at all, and their skulls were possibly brightly colored and used for display.
Another theory states that the skull may have actually been a base for a keratin horn, one in which we would never truly know what it looked liked.
If this was the case we may never truly know what these dinosaurs looked like. Then again, some who agree with this theory don’t necessarily ruin the head butting hypothesis for them.
BTW, more Pachy’s with a full feather coat please.
Well, in any case, it would seem that these creatures have remained and enigma. They have also shown that you can’t infer behavior completely just based on bones alone, and just because something is supported by a lot of people doesn’t make it necessarily true. Think about it this way, if scientists from the far future found fossils of modern day giraffes and one of the scientists suggested they did this…
…his theory would probably be in a fringe group. But they do this in real life, and you can’t infer that from fossils alone. Sometimes nature really is stranger than logic, and we can’t call something fact simply because it’s plausible or makes sense. That’s kind of what afflicted the pachycephalosaurs, and I have a feeling their image of head butting dinosaurs will continue to survive.
Join me next time as I return to everybody’s favorite theme park/death trap. This blog began with this franchise, and I think it’s time I went to where it all began.
Jurassic Park (The Novel) is next.