Why Did It Take So Long To Find Baby Dinosaurs?

Alex Johnson - Content Writer


Back in 1992, my mom gave me a magazine article to read. It was about how a guy named Steven Spielberg was making something called Jurassic Park, a theme park filled with genetically engineered dinosaurs that would be opening next year. At the time, I wanted to be a paleontologist, so I was fascinated by this new, more accurate look at dinosaurs. Also, I thought it was an article about a real dinosaur park, because I was seven years old.

Shortly after, it was explained to me that this was an article about a movie that used something called “CGI” to make dinosaurs that weren’t puppets. Less exciting, but still pretty cool. My understanding of dinosaurs was shaped by the film. I swapped out my old Tyrannosaurus rex toys—the hapless taildraggers that looked like Godzilla—for the birdier predators I saw in the movies.

Mind you, our understanding of dinosaurs has come a long way since 1993, and so have I. Now a 33-year-old man, I’ve matured—I’ll only play with feathered dinosaur toys. The Jurassic Park franchise has, meanwhile, veered away from modern science (where the feathers at?). But the original film was fairly cutting edge in one way you probably haven’t realized: it showed that baby dinosaurs were a thing.

CNN describes this image as “The world’s biggest version of the world’s most famous dinosaur.” It’s a Tyrannosaurus rex at The Field Museum in Chicago. Even today, we’re biased in favor of the biggest fossils we can find.

Now, if you’re like me and you cut your dinosaur teeth on Jurassic Park, you’re probably thinking: “Yeah, no sh*t. Of course there were baby dinosaurs. They gotta come from somewhere.” Indeed they do. But did you know that, prior to 2000, nobody had even seen a sub-adult Triceratops? The species was discovered in 1887, yet nobody had seen a juvenile—that they knew of.

The Triceratops is just one famous example. For almost as long as humans have been digging up dinosaur bones, we’ve faced a dearth of baby dinosaurs. Why? Well, the short answer is: we have big egos.

The Long Answer

In 2011, Dr. Jack Horner, paleontologist and curator of paleontology at the Museum of the Rockies, gave a TED Talk about baby dinosaurs.1. Specifically, he was asking a rhetorical question: “Where are the baby dinosaurs?”

Paleontology has been around in one form or another since 1822, but the vast majority of that time was spent not looking for baby dinosaur bones. The reason has to do with marketing: in the 19th century, museums were competitive business, and they needed to provide big attractions. People were naturally attracted to beasts that were both large and exotic, and dinosaur exhibits ticked off both of those boxes better than most extant terrestrial animals. Think of it this way: you have two museums to pick from; one has a 25-foot Megalosaurus skeleton, and the other has a 28-foot Megalosaurus skeleton. All other things being equal, you’re gonna check out that 28-footer, right? You get more dinosaur per dollar that way (or lizard, as folks in the 1820s hadn’t yet coined the term “dinosaur”).2.

Museum curators wanted to display the biggest dinosaurs they could find, and excavators looking to sell dinosaur fossils tended to oblige by finding what appeared to be large, adult dinosaur remains. The problem is that humans have never seen living dinosaurs, so we lack a solid frame of reference when it comes to the maturity of dinosaur remains.

So, we jumped to some incorrect conclusions. Today, we know that dinosaurs and modern birds share some evolutionary history. But for a long time, they were considered to be more reptilian in nature. We figured them to be cold-blooded, dim creatures that dragged their tremendous weights across the primeval landscape, rather than nimble, feathered creatures, capable of complex thought. As we understand dinosaurs now (the avian dinosaurs, anyway), they were less like my old roommate’s iguana, and more like that raven I met in Alaska that distracted me while another raven stole my lunch. Clever girl.

Just for fun, here’s a diagram showing the size of various dromaeosaurs compared to a human. Note how they look more like birds than lizards. Also note that Jurassic Park made a mistake by picking the Velociraptor as its antagonistic species, given that it’s the size of a golden retriever. Utahraptor, meanwhile, was discovered in 1991 and was exactly what they were looking for, yet did not use.

The reptilian view led to some flawed thinking: if dinosaurs were reptiles, then they must mature like reptiles. Young dinosaurs, therefore, would look like scaled down versions of their mature counterparts. That seemed logical and simple enough, and it wasn’t a big problem, anyway—museums weren’t clamoring for smaller dinosaur skeletons, and paleontologists didn’t know what they didn’t know, so there was no great mystery to be solved.

Instead of finding smaller, juvenile versions that matched mature specimens, paleontologists tended to find smaller dinosaurs that were similar, yet different enough to be considered the cousins of already established species. And from a paleontologist’s perspective, that was just fine.

Imagine you’re a paleontologist in, say, the 1920s. You’ve excavated and assembled a collection of fossils into a portion of what looks a bit like a known theropod, but is smaller and has a different configuration of horns on its head. Would you be more inclined to prove that it belonged to an already-discovered species, despite some physiological differences, or would you take one look at those weird horns and say, “holy sh*t, I just discovered and Alexandrosaur!” You’d do the second one, and you wouldn’t even be dishonest about it—they just didn’t know any better. Scientists are humans with egos, too, and they need to publish stuff in journals. Finding a repeat dinosaur was not as impressive.1

Dodson! We Got (Dr. Peter) Dodson, here!

In 1975, one smartass paleontologist came around and ruined the goldmine for the rest of the dinosaur-naming community by asking dangerous questions.

See, by the 1970s, folks started looking around museums and saying, “hey, where are the little dinosaurs?” It’s a bit like how you can play Grand Theft Auto for like 12 hours before noticing that it takes place in a version of Los Angeles that has no children—once you notice it, you can’t ignore it.

Dr. Dodson had a new idea: dinosaurs didn’t mature like reptiles—they matured like birds! Then he called our collective attention to the cassowary. If you don’t know that species name, you’d probably recognize the bird—it looks a bit like a magic turkey with a wig for a body and a blue head. I mean that with all due respect (it’s a beautiful creature). Dodson was focused on the cassowary’s crested head and, more broadly, all birds with crested skulls.

A full-crested cassowary in its final form.

Here’s the deal with crested birds: a lot of them are like the cassowary, which doesn’t grow the final version of its crest until it has already reached 80 percent of its full size. So, if some cyborg paleontologist in a few million years discovers an old cassowary fossil and a young cassowary fossil, not only would they be different sizes, but their skulls would look different. Related, yes, but different. This futuristic cyborg paleontologist, having never seen a living cassowary, might well reach the conclusion that these were two different species of birds.

Dodson’s hypothesis was compelling, and there is indeed a way to determine if you’ve got a young dinosaur’s remains, or if you’ve got mature bones: you cut ‘em open and see how spongy they are on the inside. Basic rule of thumb: younger bones are spongier than mature bones, because they’re still growing.

Hypacrosaurus—you can see why Dodson used this dinosaur’s crest maturity as a comparison to the cassowary.

He gave a solid example: the Hypacrosaurus—one of the duck-billed dinosaurs—at full growth sported a rounded crest on top of its head. If the Hypacrosaurus matured linearly (like a reptile), then at 50 percent maturity, it ought to have 50 percent of the crest that a fully grown Hypacrosaurus would have. But they had a Hypacrosaurus that had survived to 65 percent maturity—and it had no crest at all. Bingo: dinosaurs probably aged more like birds (nonlinearly) than they did like reptiles (linearly). Despite the compelling new evidence, everybody ignored Dodson, because the other paleontologists wanted to keep naming new species, rather than unnaming “new” dinosaurs that were actually juvenile versions of already-named species.1

Jack Horner, Fossil Cutter

Roughly a quarter century later, in the early 2000s, Jack Horner picked up Dodson’s torch. Like I said, you can cut open fossils to determine the animal’s maturity when it died, but most museums aren’t too keen on dicing up their big attractions—particularly skulls. Jack Horner, as both a disciple of Dr. Dodson and a guy who ran his own paleontology museum, was in a unique position: he could totally cut his fossils up—even the skulls—so he did.

Jack “Hacksaw” Horner. He can have that nickname, if he hasn’t used it already.

Traditional knowledge had determined 12 primary species of dinosaur that had been discovered thus far in North America (there are, of course, others, but these are the popular ones). Jack Horner took a bonesaw to skulls belonging to the species on this list. When he was done, there were seven left. Here are a couple of examples of how it went down:

Dracorex, Stygimoloch, and Pachycephalosaurus

These “three” dinosaur species were similar in appearance and they coexisted, yet each had varied horn and dome configurations on its head. The Dracorex’s head featured spikes, nose protrusions, and no dome. The Stygimoloch also had spikes and the nose protrusions, but only had a little dome. The Pachycephalosaurus had a big, characteristic dome on its head as well as the nose protrusions, but only little bumps on its head, rather than spikes.

Here, have this visual aid.

Horner sawed the skulls open, tested their internal sponginess, and reached his conclusion: these weren’t three different dinosaurs, but rather three pachycephalosaurs at various stages of maturity. Dracorex was the youngest, Stygimoloch a bit older, and Pachycephalosaurus was the full adult. Dracorex and Stygimoloch, therefore, were not real dinosaurs, but rather mislabeled young pachycephalosaurs. The paleontologist who “discovered” the Dracorex hogwartsia in 2006 was simply too jazzed about naming a new dinosaur after Harry Potter to have noticed that it wasn’t actually a new species. Jack Horner mercilessly relegated the Dracorex to the  “dubious species” list three years later, in 2009. Basically, that means Dracorex ain’t gonna be in the new Jurassic World: Fallen Kingdom movie (just the video game).2 3 1

Tyrannosaurus Rex and Nanotyrannus

Normally, if you were to find a dinosaur that looked just like a T. rex, only a little smaller, you’d logically think, “I’ve seen The Lost World, so I know a baby T. rex when I see one,” and then not declare discovery of a new species. But the Nanotyrannus still threw paleontologists for a loop—because it had too many teeth.

Tyrannosaurus rex and her son, Nanotyrannus. How does a T. rex get pregnant with a different type of dinosaur? It doesn’t—they’re the same species.

The biggest T. rex skull they had featured 12 teeth per jaw. Meanwhile, this little T. rex-like skull had 17 teeth per jaw. One might expect the adult version of a toothy animal to have more teeth than a juvenile, not fewer. Horner cut open that Nanotyrannus skull and found that it was nice and spongy, indicative of a youngster, which made sense for his (and Dodson’s) theory.

But this mystery was even easier to solve. Horner took his four T. rex skulls and just lined their jaw bones up—no fossil cutting required. Lo and behold: the biggest one, as mentioned, had 12 teeth. The second biggest skull had 13 teeth, the third biggest had 14, and the Nanotyrannus, again, had 17. The conclusion: T. rex had fewer teeth as it matured. Oh, and Nanotyrannus was just a young T. rex. Another species off the top 12 list.1

In Memoriam

Jack Horner’s work splitting skulls, inspired by Peter Dodson’s ideas, was great for paleontology, but if you want to make an omelette, you gotta crack some eggs. If the original list of 12 North American dinosaurs was an egg carton, Horner and his team brusquely flipped five of those eggs onto the museum floor. Their names: Stygimoloch, Dracorex, Torosaurus, Anatotitan, and Nanotyrannus. Their only crime: eternal youth.

They are survived by all the amateur dinosaur enthusiasts who memorized the spellings of their names. Some might say getting to know them was all for naught, but I disagree. These dinosaurs’ fossils are still real, they were just given fake names.

Turns out the baby dinosaurs hadn’t been hiding at all—we just didn’t realize so many of them were late bloomers.1

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Notes & Gossip 📌

  1. Horner, Jack. (November 2011). Where are the baby dinosaurs? Retrieved from https://www.ted.com/talks/jack_horner_shape_shifting_dinosaurs
  2. Jurassic Park Wiki. (Accessed June 19, 2018). Dracorex. Retrieved from http://jurassicpark.wikia.com/wiki/Dracorex#Movies
  3. Sanders, Robert. (2009, October 30). New analyses of dinosaur growth may wipe out one-third of species. Retrieved from https://www.berkeley.edu/news/media/releases/2009/10/30_dino_demise.shtml

Scholarly Shout-outs 🌟

  • Encyclopaedia Britannica. (Accessed June 15, 2018). Paleontology. Retrieved from https://www.britannica.com/science/paleontology.
  • Horner, Jack. (November 2011). Where are the baby dinosaurs? Retrieved from https://www.ted.com/talks/jack_horner_shape_shifting_dinosaurs
  • Jurassic Park Wiki. (Accessed June 19, 2018). Dracorex. Retrieved from http://jurassicpark.wikia.com/wiki/Dracorex#Movies
  • Sanders, Robert. (2009, October 30). New analyses of dinosaur growth may wipe out one-third of species. Retrieved from https://www.berkeley.edu/news/media/releases/2009/10/30_dino_demise.shtml

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