A new duckbill dinosaur from Coahuila, Mexico, and how to find a dinosaur

A new kritosaurin duckbill is described from the Late Campanian of the Cerro del Pueblo Formation, Coahuila; on the best way of finding new fossil species

Holotype of Coahuilasaurus lipani

Recently my colleagues and I named a new hadrosaur from northern Mexico, Coahuilasaurus lipani. I say discovered, not in the sense you might think, in that we found bones in the desert and dug them up. Rather, we recognized it as a new species after studying the specimen at the museum in Mexico City.

The partial skull of Coahuilasaurus was originally found in a block of sandstone in the desert of Coahuila back in the 1980s by a team from the Geological Institute at the National Autonomous University of Mexico. The skull wasn’t described until 2006, however, when it was identified as an unknown species of Kritosaurus. The skull was later assigned to Kritosaurus navajovius, a species from the Campanian of New Mexico, in a 2014 paper. Our restudy suggests it’s related to Kritosaurus, as part of the tribe Kritosaurini, but it’s a new species, closer to Gryposaurus monumentensis from Utah than to Kritosaurus.

It might seem a bit counterintuitive to hunt dinosaurs in museums. But it’s like the old joke about the reporter who asked a bank robber who was asked why he robbed banks. Because, he said, “that’s where the money is.”

Museums are a good place to hunt dinosaurs, because that’s where the fossils are.

Fossils exist at a much higher density in museums than they do in deserts. In the badlands you’d be incredibly lucky to find one dinosaur in a day, or even a week. In a museum you can see dozens in an afternoon. Even if most of them don’t turn out to be anything new, you can see a huge number of fossils in a short period of time, so you actually have a pretty good chance of coming across something novel.

The Cerro del Pueblo Formation, in Coahuila State, Mexico

A lot of people think hunting dinosaurs is a bit like the Indiana Jones movies. It kinda is, in a strange way.

If you remember the final scene of Raiders of the Lost Ark, having saved the Ark of the Covenant and defeated the Nazis, Indiana Jones asks what they’ll do with the Ark.

                  “We have top men working on it,” says the government guy.

                  “Who?” asks Indiana Jones.

                  “Top men.”

                            The Ark of the Covenant is then wheeled off into the vast maze of a warehouse where it disappears into a labyrinth of crates and wooden boxes, the music swells. It’s one of the most iconic endings in cinema, but it’s got a lot of truth to it.

You might assume things in museums are meticulously organized and carefully identified. In reality, collections are often chaotic places. They’re full of unopened crates and plaster jackets, nobody ever seems to know where anything is. Specimens in museums are collected over many years, shuffled around, misidentified, stashed away in drawers and forgotten about. Anything could be in there, like that giant warehouse. Recently when I went to see the holotype of the tyrannosaur Labocania in Mexico City, but we couldn’t find it. Actually, it wasn’t just that people couldn’t find it, they didn’t even realize it was in the collections— I was told it was in the museum in Los Angeles. We had to ask around and only after I left could we find someone who knew where it was in the collections, it took a second trip to get to study it.

All kinds of things lie hidden in museums.

Lost treasures like new tyrannosaurs, new horned dinosaurs, and new duckbill dinosaurs.

There’s another way that paleontology is a bit like Raiders of the Lost Ark. If you remember the start of the movie, Indiana Jones finds a golden idol, which triggers a series of booby-traps— poison arrows, a giant boulder that tries to crush him, and so on. He narrowly escapes, only to find himself cornered by his rival and enemy, the archaeologist Rene Belloq. Belloq grabs the golden idol from Jones.

Taunting him, Belloq smirks and says, “Again we see there is nothing you can possess which I cannot take away.”

The lesson here is that finding things is hard work. So its often just easier to outsource the hard part of the research, to let other people find stuff, and then come in and make the discovery. The hardest part of describing the skull of a new Velociraptor species, isn’t writing up the paper (which takes work, but is fairly straightforward, and the outcome is fairly predictable), it’s finding the skull (which is anything but straightforward, and highly unpredictable).

But in a museum, the hard part- finding the dinosaur- has already been done for you. This leaves only a relatively easy problem. Recognizing what it is you have in your hands.

The reason I spend a lot of time hunting dinosaurs in museums is because it’s easy.

Of course, I’m not advocating stealing people’s specimens like Belloq would. But very often things get found, and then forgotten about, or misidentified.

Discovery takes a whole series of steps.

A fossil must be found in the field,

dug up,

taken to a museum,

catalogued,

prepared, and so on…

and then somewhere along the way, it has to be recognized as something new. It must be identified. Sometimes it’s never studied at all. And sometimes even after it’s published on, its still not properly identified.

That was the case with Coahuilasaurus. It’s related to Kritosaurus, but it’s actually something different, closer to Gryposaurus monumentensis and Rhinorex.

Evolutionary tree of Saurolophinae, showing the relationships of Coahuilasaurus within Kritosaurini

I’m being perhaps a bit facetious, or maybe engaging in false modesty when I say that the identification is the easy part. Yes, in some ways, it is relatively easy. Sometimes you just glance at a fossil and you know what it is. Maybe it takes you a few hours sitting down with papers and photographs. Occasionally, if it’s a hard problem, it takes a few weeks of close study to figure out just what you have.

But being able to recognize what a fossil is, that also requires skills and knowledge that can take years, even a career to develop. In Morocco I recognized the little duckbill Ajnabia at a glance, but to be able to recognize it in a glance was the result of a PhD, a postdoc, many years of fieldwork and collections visits, writing papers, getting papers rejected, and so on. It took three seconds to recognize it, three seconds and a career. And even when you figure out what it is, the process of publishing it can take months or years.

One isn’t necessarily better than the other.

Finding a bone in the desert and digging it up takes hard work.

Identifying it takes hard work.

They’re both important and essential parts of the process. Paleontology can’t happen without both. The point being, some people excel at finding fossils in the field. I have huge respect for these people, they make my papers possible, but I am not one of them. Other people are good at identifying fossils. This is where I have tended to focus my efforts.

Last, in studying museum collections, a healthy skepticism is very important.

the wing bone of an unknown bird species from the Late Campanian of Alberta, 75 million years ago

My first paper was on the wing bone of a Cretaceous bird. I was rummaging through the drawers of the Tyrrell Museum trying to learn more about dinosaur anatomy. One drawer was largely empty except for a few small boxes. In one of these was a bone labeled as part of a theropod finger bone. I took one glance and knew it was misidentified— I’d collected a lot of bird skeletons off beaches, and dissected birds to learn about bird evolution. It wasn’t a theropod knuckle joint. It was part of an avian carpometacarpus. I wrote it up, and this little fossil became my first paper. This taught me a valuable lesson.

There’s stuff in museums that misidentified. You shouldn’t blindly trust the specimen cards.

Someone comes along, makes a guess about what it is in the field, and it enters the museum database and is labeled with that guess. Most of the time, that first guess is right, but out of thousands of fossils, there will be a fair number of misidentifications, especially if you’re dealing with something new, or rare, that no one has seen before.

I’m not saying they’re all wrong, but enough of them are that it’s worth carefully double-checking the identifications. If the IDs are correct, then you’ve learned something. Now you know how to identify that species, or that bone. If they’re wrong, then you’ve also learned something- maybe part of the skeleton of a species that wasn’t known before, or sometimes, you have an entirely new species.

Most of the time, people can’t be bothered to double-check the identifications. But even assuming fairly high accuracy- 99% of the fossils in a museum are correctly identified- then in a collection of 10,000 specimens, there must be at least 100 misidentified fossils.

And identifying fossils is incredibly challenging, in part because the taxonomic key against which we’re comparing things is always being updated. Birds are pretty well-known, a bird guide from 20 years ago is about as good as a modern bird guide. Imagine trying to identify birds if birds were being reclassified and new ones discovered every five years.

Tyrannosaurus mcraeensis, a new tyrannosaur my colleagues and I "discovered" in the collections in Albuquerque.

And so over the years, I found a series of other animals that were misidentified or unidentified, lurking in museum drawers — the little theropods Hesperonychus, Albertonykus. Other animals, like Titanoceratops and Tyrannosaurus mcraeensis, were actually on display in museums, and published on, but misidentified, as Pentaceratops and T. rex, respectively. Again, most of the time people find it easier to just assume the published identifications are correct. And most of the time they are. But sometimes they’re not, and that’s where it gets interesting.

It’s also helpful to know when you need to be skeptical.

In the case of Coahuilasaurus, the animal was originally described as Kritosaurus sp., and then as Kritosaurus navajovius. But what we’ve learned about North American dinosaurs over the past 20 years makes it very unlikely that this animal could be Kritosaurus, since it comes from a different rock formation.

This is because of evolution.

When you prospect the Dinosaur Park Formation in Canada, for example, you get different species at different levels. For horned dinosaurs, you see Centrosaurus at the base of the formation, then Styracosaurus in the rock layers above that, Pachyrhinosaurus at the very top of the formation. Duckbills change too, with Lambeosaurus lambei giving way to Lambeosaurus magnicristatus over time. And so on.

In the old H.G. Wells science fiction novel, the Time Machine, the time machine can’t actually move. Instead, the Time Traveler just moves forwards and back through time while the world around him changes, as civilizations rise and fall, and humans evolve into new species, then go extinct, and other things appear. Walking up and down the outcrop is like a time machine. The world around you changes. The dinosaurs all around evolve, old species go extinct, and new ones appear. Go up high enough, dinosaurs disappear entirely, as you hit the iridium layer where the asteroid hit.

To find new species, just move up or down through the rock layers. You travel forward and back through time, to new times, you see new species. Dinosaurs were surprisingly short-lived, lasting perhaps a million or half a million years. A few tens of meters up or down the stratigraphic column can be enough to reveal entirely unknown species.

Now, in the case of the Coahuila kritosaur, it seems to be substantially younger than Kritosaurus itself, maybe a million years younger. That piece of information alone very strongly implies that we’re dealing with a new species. It’s not certain, but a pretty good bet.

Not only do we see different dinosaurs at different times, we see different dinosaurs in different parts of the continent. Again, that’s due to evolution. Dinosaur species migrated and colonize new habitats. Once invading a habitat, they evolved- they’d adapt to the local climate, to the plants, and diseases. The mating preferences might drive their crests and horns to evolve in one direction in one part of the continent, another way in another part of the continent. So in a million years or less (remember, a million years is a long time!) we get different species in different places.

So again, the fact that we’re sampling a new formation, a thousand miles from where Kritosaurus was found, implied the Coahuila duckbill would likely be something new. None of the species found so far in Coahuila— Velafrons, Tlatolophus, Coahuilaceratops— are known from the United States or Canada. Coahuila had its own distinct fauna, distinct from contemporary species found in the Horseshoe Formation of Canada. If everything else there is unique that strongly implies that the duckbill isn’t going to be a known species, either.

Kritosaur diversity.

A plethora of kritosaurs roamed the Western Interior of North America, distinguished by subtle variations in their jaws, teeth, skull roof, and nasal crest.

So I went into the collections almost certain the Coahuila hadrosaur was something new. Still, it took us a while to figure out exactly what we did have.

The new species is represented by just the front of the skull- although in much the same way different species of birds, like ravens and crows have different beaks, dinosaurs do too. They seem to be evolving rapidly in response to the local vegetation, so details of the beak are actually a good way to tell species apart.

Crows, Corvus brachyrhynchos (left) and ravens, Corvus corax (right) are distinguished by different beak shapes

These differences, subtle and not so subtle, suggested we didn’t have a Kritosaurus. The jaws were too robust, the chin was too prominent. Overall, comparisons suggested it was probably more closely related to Gryposaurus monumentensis from the Campanian of Utah. But again, there were differences between this animal and monumentensis. The beak was subtly (and not so subtly) different. The nostril was longer, the curvature of the narial bar was unusual. The corner of the beak was more squared-off. Admittedly, many of these differences are subtle, but so are a lot of the differences distinguishing modern dinosaurs, the birds.

One feature, though, really stood out- a huge set of toothlike processes projecting downward, which would have been covered in tough keratin in life. Although a number of duckbills have these toothlike projections around the edge of the beak, in Coahuilasaurus, they project down from the roof of the mouth. It’s bizarre and unlike any other duckbill I’ve ever seen. Presumably, it is an adaption for some kind of tough flora- palms? Cycads? Banana plants? No idea. But it was presumably doing something a bit different than the other kritosaurs.

Coahuilasaurus beak, in anterior view.

A series of massive, toothlike structures project down from the roof of the mouth. Presumably they functioned to help the beak seize and tear tough plant matter.

 So, many years after the specimen was first dug up, almost 20 years after it was first described in the literature, we finally have discovered what this thing is, that it’s something new. This sort of thing is actually pretty common.

Dinosaurs were spectacularly, phenomenally diverse, and there’s still a lot more dinosaurs out there waiting to be found and recognized. Today there are over a thousand named species of dinosaurs, with more discovered and named every year. This might be surprising, after all we have been working on dinosaurs for more than 200 years.

But we haven’t even found all the living species- we have most of the birds, but not all of them, we’re still finding new whales, new monkeys, and new cats. It might seem bizarre that something as large as a whale could go undiscovered, but the ocean is a big place. We probably haven’t even found half the beetle species that exist, simply because there are so many species, and they’re tiny and hard to find. We’re probably missing the vast majority of fungi. Life’s diversity is, well, diverse.

This is even more true of the past, which is so much more difficult to study. Dinosaurs were diverse- lots of species in each habitat, different species in different habitats, and they evolved rapidly as the flora, the climate, and the landscape shifted.

Coahuilasaurus lipani, by C. Díaz Frías, 2023

                  And some places are just more poorly known- they have more species, which makes it difficult to find them all, we have fewer fossils, or the fossils just aren’t as well-studied. All of these things seem to be true of Mexico. While we continue to find new species in well-explored places like Alberta, Montana, and Wyoming, our knowledge there is relatively complete. The knowledge gap- the gap between what we know, and what remains undiscovered- is just bigger in Mexico. There’s a lot left to be done, more dinosaurs waiting to be found, in the museum, and in the desert. .

References

Brown, B., 1910. The Cretaceous Ojo Alamo beds of New Mexico with a description of the new dinosaur genus Kritosaurus. Bulletin of the American Museum of Natural History 28, 267-274.

Kirkland, J.I., Hernández-Rivera, R., Gates, T., Paul, G.S., Nesbitt, S., Serrano-Brañas, C.I., Garcia-de la Garza, J.P., 2006. Large hadrosaurine dinosaurs from the latest Campanian of Coahuila, Mexico. New Mexico Museum of Natural History and Science Bulletin 35, 299-315.

Longrich, N., 2006. An ornithurine bird from the Late Cretaceous of Alberta, Canada. Canadian Journal of Earth Sciences 43, 1-7.

Longrich, N.R., 2011. Titanoceratops ouranos, a giant horned dinosaur from the Late Campanian of New Mexico. Cretaceous Research 32, 264-276.

Longrich, N.R., Currie, P.J., 2009. Albertonykus borealis, a new alvarezsaur (Dinosauria: Theropoda) from the Early Maastrichtian of Alberta, Canada: Implications for the systematics and ecology of the Alvarezsauridae. Cretaceous Research 30, 239-252.

Longrich, N.R., Currie, P.J., 2009. A microraptorine (Dinosauria-Dromaeosauridae) from the Late Cretaceous of North America. PNAS 106, 5002-5008.

Longrich, N.R., Dalman, S., Loewen, M., Pyron, R., Jasinski, S.E., Malinzak, D., Lucas, S., Fiorillo, A., Currie, P.J., 2024. A giant tyrannosaur from the Campanian-Maastrichtian of Southern North America and the origins of Tyrannosaurus, Society of Vertebrate Paleontology, Cincinnati, Ohio.

Longrich, N.R., Velasco, A.A.R., Kirkland, J., Torres, A.E.B., Serrano-Brañas, C.I., 2024. Coahuilasaurus lipani, a New Kritosaurin Hadrosaurid from the Upper Campanian Cerro Del Pueblo Formation, Northern Mexico. MDPI Diversity 16.

Prieto-Márquez, A., 2014. Skeletal morphology of Kritosaurus navajovius (Dinosauria: Hadrosauridae) from the Late Cretaceous of the North American south-west, with an evaluation of the phylogenetic systematics and biogeography of Kritosaurini. Journal of Systematic Palaeontology 12, 133-175.