Paleo Profile: Mexico’s Mystery Dinosaur

Centrosaurine sites in North America. From Rivera-Sylva et al., 2016.
Centrosaurine sites in North America. From Rivera-Sylva et al., 2016.

A few years back, while crashing at my apartment for the night during a long trip west, a friend of mine asked me “Haven’t paleontologists found all the dinosaurs already?” Museums from coast-to-coast seem well-stocked with primordial reptiles, and, really, when dealing with such giants, how many species could there possibly be? I had to chuckle at my friend’s question. Not only were there more dinosaur species than we ever imagined, but we’re still a long way from finding them all.

I can’t think of a place that better exemplifies the dinosaur boom than North America’s southwest. Hell, the fantastic new species coming out of the area from the four corners on south was half the reason I moved to Utah. New explorations in the western deserts have yielded an increasing array of new dinosaur species, and paleontologists already know that there’s more out there than has been formally identified. Take, for example, an animal represented by a smattering of bones found in northern Mexico.

There is no formal name for this dinosaur yet. There’s too little of it to justify a permanent identification. But, as described by paleontologist Héctor Rivera-Sylva and colleagues, the fossils appear to represent a horned dinosaur not seen before.

The bones were found in Coahuila, northern Mexico, between 2007 and 2011. And while paleontologists named another horned dinosaur – Coahuilaceratops – from this area in 2010, the bones described by Rivera-Sylva and coauthors are from something different. That’s because Coahuilaceratops is what experts call a chasmosaurine – the lineage that contains Chasmosaurus and Triceratops – while this new dinosaur belongs to a separate lineage called centrosaurines that includes Centrosaurus, Nasutoceratops, and their relatives. This makes CPC 274 the southernmost occurrence of a centrosaurine dinosaur yet found.

This is how some dinosaurs make their debut. Not as beautiful skeletons with names as awesome as their osteology, but as fragments and pieces that hint at what’s left to find. The recently-named tyrannosaur Timurlengia, for example, first came to paleontologists as a smattering of tantalizing fragments before a braincase tied everything together. Hopefully the Coahuila centrosaurine will follow the same pattern, new finds filling in the identity of what must have been a gnarly herbivore with its own splay of spikes and horns.

I look forward to the day that paleontologists will be able to organize an unveiling for Mexico’s mystery dinosaur, but that’s not the point of this post. I picked this unnamed enigma for my last Paleo Profile here at National Geographic because of what it represents. The unknown is what calls to scientists, both in the lab and in the layers of time laid out in the desert. For every fact or fossil we find, we get a bloom of new questions that itch at the brain and the soles of your boots. That’s the drive to seek out unknown dinosaurs in their remote, ancient tombs, and, truly, we are just getting started.

centrosaurine-squamosal

Fossil Facts

Name: There is no genus and species name yet. For now the dinosaur is designated as specimen CPC 274.

Age: About 80 million years ago.

Where in the world?: Coahuila, Mexico.

What sort of critter?: A horned dinosaur related to Centrosaurus.

Size: Unknown.

How much of the creature’s body is known?: A partial skull and several pieces of the postcrania.

Reference:

Rivera-Sylva, H., Hedrick, B., Dodson, P. 2016. A centrosaurine (Dinosauria: Ceratopsida) from the Aguja Formation (Late Campanian) of northern Coahuila, Mexico. PLOS ONE. doi: 10.1371/journal.pone.0150529

Previous Paleo Profiles:

The Unfortunate Dragon
The Cross Lizard
The South China Lizard
Zhenyuan Sun’s dragon
The Fascinating Scrap
The Sloth Claw
The Hefty Kangaroo
Mathison’s Fox
Scar Face
The Rain-Maker Lizard
“Lightning Claw”
The Ancient Agama
The Hell-Hound
The Cutting Shears of Kimbeto Wash
The False Moose
“Miss Piggy” the Prehistoric Turtle
Mexico’s “Bird Mimic”
The Greatest Auk
Catalonia’s Little Ape
Pakistan’s Butterfly-Faced Beast
The Head of the Devil
Spain’s Megatoothed Croc
The Smoke Hill Bird
The Vereda Hilarco Beast
The North’s Sailback
Amidala’s Strange Horn
The Northern Mantis Shrimp
Spain’s High-Spined Herbviore
Wucaiwan’s Ornamented Horned Face
Alcide d’Orbigny’s Dawn Beast
The Shield Fortress
The Dragon Thief
The Purgatoire River’s Whale Fish
Russia’s Curved Blade
The Dawn Mole
The Oldest Chameleon
The Wandering Spirit
Teyú Yaguá
New Caledonia’s Giant Fowl
The Giant Tarasque Tortoise
The Giant, Bone-Crushing Weasel
The Dawn Rough Tooth

Paleo Profile: The Dawn Rough Tooth

The reconstructed skull of Eotrachodon. From Prieto-Márquez et al., 2016.
The reconstructed skull of Eotrachodon. From Prieto-Márquez et al., 2016.

Eastern dinosaurs are hard to find. Between geologic happenstance, suburban sprawl, and forests that blanket what would otherwise be promising outcrop, we know frustratingly little about the dinosaurs of Appalachia compared to their relatives exposed in the deserts to the west. But every now and then paleontologists are able to pull a prize out of the difficult eastern exposures. The hadrosaur Eotrachodon is one such case.

Paleontologists  Albert Prieto-Márquez, Gregory Erickson, and Jun Ebersole named the dinosaur earlier this year from bones found in Alabama. The remains are pretty scrappy, which is typical for Appalachian finds, but Eotrachodon is nevertheless known from a nearly-complete skull that provides a rich source of osteological comparison for other hadrosaurs. After all, most hadrosaurs are primarily identified by their skulls – different ornamentation on a very conservative chassis.

At about 85 million years old, Eotrachodon lived about 10 million years before the great profusion of its more famous cousins in the west like Parasaurolophus, Lambeosaurus, and their ilk. In fact, Prieto-Márquez and colleagues found, Eotrachodon seems to fall right outside the split between the major crested and crestless hadrosaur lineages, hinting that the eastern half of North America was the place hadrosaurs started to take off before conquering so much of the west.

But there’s another reason I picked Eotrachodon for this week’s Paleo Profile. When I was a kid the hadrosaur Trachodon often made appearances in books and movies, but paleontologists abandoned the name. That’s because the name Trachodon is formally chained to a handful of isolated teeth that can’t be tied back to a body. By coining the name Eotrachodon, however, Prieto-Márquez and coauthors found a workaround to revive the classic title and give poor “Trachodon” a new dawn.

The right maxilla of Eotrachodon. From Prieto-Márquez et al., 2016.
The right maxilla of Eotrachodon. From Prieto-Márquez et al., 2016.

Fossil Facts

Name: Eotrachodon orientalis

Meaning: Eotrachodon means “dawn Trachodon” (or “dawn rough tooth” fully translated), and orientalis is a reference to the fact this dinosaur was found in America’s southeast.

Age: About 85 million years ago.

Where in the world?: Montgomery County, Alabama.

What sort of critter?: A hadrosaur, or “duck-billed” dinosaur.

Size: Comparable to other North American hadrosaurs such as Hadrosaurus and Gryposaurus.

How much of the creature’s body is known?: A nearly-complete skull and fragmentary elements of the postcrania.

References:

Prieto-Márquez, A., Erickson, G., Ebersole, J. 2016. A primitive hadrosaurid from southeastern North America and the origin and early evolution of ‘duck-billed’ dinosaurs. Journal of Vertebrate Paleontology. doi: 10.1080/02724634.2015.1054495

Prieto-Márquez, A., Erickson, G., Ebersole, J. 2016. Anatomy and osteohistology of the basal hadrosaurid dinosaur Eotrachodon from the uppermost Santonian (Cretaceous) of southern Appalachia. PeerJ. doi: 10.7717/peerj.1872

Previous Paleo Profiles:

The Unfortunate Dragon
The Cross Lizard
The South China Lizard
Zhenyuan Sun’s dragon
The Fascinating Scrap
The Sloth Claw
The Hefty Kangaroo
Mathison’s Fox
Scar Face
The Rain-Maker Lizard
“Lightning Claw”
The Ancient Agama
The Hell-Hound
The Cutting Shears of Kimbeto Wash
The False Moose
“Miss Piggy” the Prehistoric Turtle
Mexico’s “Bird Mimic”
The Greatest Auk
Catalonia’s Little Ape
Pakistan’s Butterfly-Faced Beast
The Head of the Devil
Spain’s Megatoothed Croc
The Smoke Hill Bird
The Vereda Hilarco Beast
The North’s Sailback
Amidala’s Strange Horn
The Northern Mantis Shrimp
Spain’s High-Spined Herbviore
Wucaiwan’s Ornamented Horned Face
Alcide d’Orbigny’s Dawn Beast
The Shield Fortress
The Dragon Thief
The Purgatoire River’s Whale Fish
Russia’s Curved Blade
The Dawn Mole
The Oldest Chameleon
The Wandering Spirit
Teyú Yaguá
New Caledonia’s Giant Fowl
The Giant Tarasque Tortoise
The Giant, Bone-Crushing Weasel

Paleo Profile: New Caledonia’s Giant Fowl

A restoration of Sylviornis. From Worthy et al., 2016.
A restoration of Sylviornis. From Worthy et al., 2016.

Life gets weird on islands. Some species, such as elephants, shrink over time, while forms of life that are tiny on the mainland expand to unheard of sizes. Among the best examples of this Island Rule—which is really more of an Island Puzzle—are birds. Over and over again, islands have hosted populations of ground-dwelling, supersized birds, such as one hefty fowl that strutted around New Caledonia.

François Poplin named the bird Sylviornis neocaledoniae in 1980. Exactly what sort of avian it was, however, has been in dispute ever since then. Poplin considered the helmet-headed bird to be related to cassowaries and emus, while other experts suggested that Sylviornis was much closer to turkey-like megapodes. Then further analysis of the skull led other avian experts to put Sylviornis in its own special lineage, the Sylviornithidae, asserting that the turkey-like features of the birds bones were a case of convergence.

In order to sort through this tangle, paleontologist Trevor Worthy and colleagues had a look at about 600 bones of the bird’s body. What they found supported some earlier suggestions about where the bird nested in the greater avian family tree – Sylviornis was a stem galliform, or a relatively archaic member of the group that contains turkeys, pheasants, and chickens. And this might rule out Sylviornis as the answer to a New Caledonian mystery.

Strange earthen mounds on New Caledonia were thought to be the nests of the massive Sylviornis. But this connection relied on the idea that the big bird was a megapode, as these birds characteristically deposit warm their eggs in holes or little hillocks of soil to gain warmth from rotting vegetation, the earth, or some other outside source. Now that Worthy and coauthors have pushed Sylviornis further away from the megapodes, the idea that the mystery mounds were made by Sylviornis now seems less likely. The anatomy of the bird’s feet, the researchers conclude, was at best suited to scratching at the dirt as if it were a supersized chicken. Perhaps, as paleontologists scratch at the soil themselves, they’ll uncover more clues about the life and times of this long-lost fowl.

Some of the Sylviornis long bones examined in the study. From Worthy et al., 2016.
Some of the Sylviornis long bones examined in the study. From Worthy et al., 2016.

Fossil Facts

Name: Sylviornis neocaledoniae

Age: Over 5,500 years ago until about 3,000 years ago.

Where in the world?: New Caledonia

What sort of critter?: A bird related to landfowl like turkeys and pheasant.

Size: Over two and a half feet tall and more than 60 pounds.

How much of the creature’s body is known?: Thousands of individual elements from the skeletons of multiple individuals.

Reference:

Worthy, T., Mitri, M., Handley, W., Lee, M., Anderson, A., Sand, C. 2016. Osteology supports a steam-galliform affinity for the giant extinct flightless birds Sylviornis neocaledoniae (Sylviornithidae, Galloanseres). PLOS ONE. doi: 10.1371/journal.pone.0150871

Previous Paleo Profiles:

The Unfortunate Dragon
The Cross Lizard
The South China Lizard
Zhenyuan Sun’s dragon
The Fascinating Scrap
The Sloth Claw
The Hefty Kangaroo
Mathison’s Fox
Scar Face
The Rain-Maker Lizard
“Lightning Claw”
The Ancient Agama
The Hell-Hound
The Cutting Shears of Kimbeto Wash
The False Moose
“Miss Piggy” the Prehistoric Turtle
Mexico’s “Bird Mimic”
The Greatest Auk
Catalonia’s Little Ape
Pakistan’s Butterfly-Faced Beast
The Head of the Devil
Spain’s Megatoothed Croc
The Smoke Hill Bird
The Vereda Hilarco Beast
The North’s Sailback
Amidala’s Strange Horn
The Northern Mantis Shrimp
Spain’s High-Spined Herbviore
Wucaiwan’s Ornamented Horned Face
Alcide d’Orbigny’s Dawn Beast
The Shield Fortress
The Dragon Thief
The Purgatoire River’s Whale Fish
Russia’s Curved Blade
The Dawn Mole
The Oldest Chameleon
The Wandering Spirit
Teyú Yaguá

Paleontologists Uncover the Tiniest Bonehead Dinosaur

Pachycephalosaurus at the North Carolina Museum of Natural Sciences. Photo by Brian Switek.
Pachycephalosaurus at the North Carolina Museum of Natural Sciences. Photo by Brian Switek.

The trio of bones were some of the smallest pieces of dinosaur I had ever seen. Royal Ontario Museum paleontologist David Evans brought the rugose, chocolate colored pieces in a box smaller than my hand, set down next to a cast of a young dinosaur’s skull that looked absolutely enormous by comparison. Despite the difference in scale, though, the facsimile cranium and the authentic fossils shared a great deal in common and revealed the identity of the animal Evans had brought out to show me. What I was looking at was the smallest Pachycephalosaurus ever found.

Pachycephalosaurus stands out in the dinosaur pantheon as the largest, last, and, thanks to The Land Before Time and Jurassic Park: The Lost World, most famous of the “bonehead” dinosaurs. They roamed western North America in the same haunts as Tyrannosaurus and Triceratops between 68 and 66 million years ago, their thick, rounded skull domes highlighted by a tonsure of little spikes surrounding the outer edge. And, as is the case with most dinosaurs, the name of the species conjures up images of the adult animals in the prime of life, yet we know that Pachycephalosaurus started out life as tiny hatchlings. The small skull bones Evans and Mark Goodwin have described get us closer than every before to the early days of this thick-skulled dinosaur.

The bones of the young Pachycephalosaurus next to a cast of "Dracorex" in the ROM collections. Photo by Brian Switek.
The bones of the young Pachycephalosaurus next to a cast of “Dracorex” in the ROM collections. Photo by Brian Switek.

The three bones—part of the cheek, the midline bone at the back of the skull, and a bone with small spikes jutting from it—were found in two Hell Creek Formation bonebeds in Garfield County, Montana. It’s literally a handful of material, but the combination of bumps and knobs and spikes on the three bones allowed Evans and Goodwin to confirm that the pieces really did belong to a very young Pachycephalosaurus. In fact, the three help tie together a hypothesis that has turned three different dinosaurs into one.

Up until about 2009, paleontologists identified three different pachycephalosaurs from the Hell Creek Formation. There was a small, flat-headed form called Dracorex, a dome-headed mid-size species with large spikes called Stygimoloch, and the classic, large Pachycephalosaurus. But in that year Goodwin and Jack Horner proposed that Dracorex and Stygimoloch were really just immature Pachycephalosaurus, the differences in their skulls being signs of growth rather than different species.

Here’s where the baby skull comes in. The stubby points on the bone from the back of the skull, the squamosal, are clustered in the same way as “Dracorex,” “Stygimoloch,” and some adult-stage Pachycephalosaurus skulls. These spikes became set very early in life. Likewise, the flat bone from the skull roof shows ornamentation similar to that of “Dracorex” as well as the beginnings of a “void space” inside from the beginnings of dome growth. So even though some aspects of skull ornamentation changed throughout the growth of Pachycephalosaurus, the anatomical groundwork was already set in place when these dinosaurs were juveniles.

So Pachycephalosaurus were fairly spiky early on. They didn’t start to grow ornaments with the onset of sexual maturity, but already had knobbly skulls in the early years of their lives. And while distinctive, these points and bumps wouldn’t have offered any defense against predators lurking in those Cretaceous woodlands. Instead, Evans and Goodwin point out, the spikes and domes in different arrangements might have been signals of age class, allowing Pachycephalosaurus to pick out who’s who in a crowd. In other words, these dinosaurs were showoffs from the time they were born.

Reference:

Goodwin, M., Evans, D. 2016. The early expression of squamosal horns and parietal ornamentation confirmed by new end-stage juvenile Pachycephalosaurus fossils from the Upper Cretaceous Hell Creek Formation, Montana. Journal of Vertebrate Paleontology. doi: 10.1080/02724634.2016.1078343

Most Dinosaur Species Are Still Undiscovered

Just about every two weeks, we meet a new dinosaur species. Some come fresh from the desert. Others have been hiding in museum collections for decades, or were misidentified as different species. However they’re found, though, dinosaurs are stomping out onto the public stage at a greater rate than ever before. Just last week, for example, paleontologist Hans-Dieter Sues and colleagues named a new, tiny tyrannosaur that once scampered around prehistoric Uzbekistan.

And if the latest estimate is correct, we’re not even close to hitting Peak Dinosaur yet.

We’ll never know precisely how many non-avian dinosaurs roamed the planet between their origin 235 million years ago and their decimation 66 million years ago. The fossil record is not complete—animals that lived in upland environments scoured by erosion had poor chances of being preserved, for instance—and that’s not accounting for sampling bias dictated by researcher interests and what field specialists can actually remove from the rock.

Even then, most of what we know about dinosaurs comes from their skeletal remains. This lets us tell the difference between Tyrannosaurus and Triceratops, but, like some modern birds and reptiles, some non-avian dinosaur species may have differed only in color, geographic range, or other squishy features that we just don’t have access to. Even if we had the bones of every single dinosaur, we’d still probably underestimate the true number of species.

Still, given these caveats, University of Oslo researchers Jostein Starrfelt and Lee Hsiang Liow have created a new model they call TRiPS to estimate how many dinosaur species were around during the Triassic, Jurassic, and Cretaceous chapters of their history.

Visitors passing by the skeletons of dinosaurs in the Humboldt Museum fur Naturkunde in Berlin, Germany. Photograph by VPC Photo, Alamy
Visitors passing by the skeletons of dinosaurs in the Humboldt Museum fur Naturkunde in Berlin, Germany. Photograph by VPC Photo, Alamy

Drawing from known dinosaur records in the Paleobiology Database, the researchers extended the known record into estimations of origin and extinction for dinosaur species throughout their history and included a simulation of how likely it’d be for species to enter the fossil record.

In all, Starrfelt and Liow write, the heyday of the dinosaurs saw the comings and goings of about 1,936 different species. About half this count are expected to be theropods—the lineage that includes T. rex and birds—with the rest split between the long-necked sauropodomorphs and ornithischians such as the armored, horned, and duckbilled dinosaurs.

Starrfelt and Liow acknowledge that they’re dealing with estimates and that refinements will likely alter their dinosaur count. But, for a first run, the results came out similar to what’s been proposed before. In 2006 paleontologists Steve Wang and Peter Dodson estimated that around 1,844 genera of dinosaurs lived during the Mesozoic. While the categories are different—a genus can contain multiple species, like Triceratops horridus and Triceratops prorsus—many dinosaurs described so far are what paleontologists call monospecific, or have only one species in a genus. This affects estimates drawn from the known span of dinosaur discoveries, and might be why the species count isn’t even higher.

The last time anyone did a major count, about eight years ago, paleontologists recognized about 648 valid genera and 675 species of Mesozoic dinosaur, including birds. Those numbers have continued to shift. In 2010, eight new dinosaur species were found in Utah alone, and debates over lumping genera or species continue, as tortured Torosaurus knows. And if the current estimates of dinosaur diversity are correct, discovery and debate will keep a frantic pace for decades to come. We’ve only just started to find all the dinosaurs, much less understand the lives of these impressive creatures.

Reference:

Starrfelt, J., Liow, L. 2016. How many dinosaur species were there? Fossil bias and true richness estimated using a Poisson sampling model. Philosophical Transactions of the Royal Society B. doi: 10.1098/rstb.2015.0219

It’s a Girl! Paleontologists Examine Pregnant T. rex

Sexing a dinosaur isn’t easy.

As far as gross skeletal anatomy is concerned, male and female dinosaurs are practically identical. And the shape of saurian bones provides no help. So far as anyone has been able to tell, the skeletons of dinosaurs were not sexually dimorphic (or, in other words, different between males and females). Even in highly-ornamented species of horned dinosaurs, armored dinosaurs, and others, all the gnarly spikes and plates and crests don’t show a definitive split in form that can be taken as a marker of different sexes.

But the evolutionary architecture of bones isn’t everything. A pair of surprises provided opportunities for paleontologists to identify some female dinosaurs, at least. In 2005 paleontologist Tamaki Sato and coauthors reported on a fossil of a parrot-like oviraptorosaur that had been preserved with a pair of eggs nestled between her hip bones. This dinosaur was definitely a female.

Better yet, just a few months later molecular biologist Mary Schweitzer and her colleagues reported on another way female dinosaurs could be identified through their pregnancies. A thigh bone of a Tyrannosaurus rex—MOR 1125 or “B. rex” to fossil fans—had a special tissue inside the main cavity called medullary bone. The same type of bone is seen in living birds, and is laid down when estrogen skyrockets following ovulation. In short, if you see medullary bone, you’ve found a pregnant female.

Art by Mark Hallett.
Art by Mark Hallett.

Not everyone agreed with this interpretation. Other experts suggested that the messy, rapidly-deposited bone tissue inside the T. rex was from a disease and that similar types of bone found in the jaws of male and juvenile pterosaurs—the flying relatives of dinosaurs—meant that medullary bone can’t be taken as a reliable indicator of a dinosaur’s sex.

But Schweitzer and a multidisciplinary team of experts have now answered these criticisms with a new study of the original T. rex clue. What did they find? That MOR 1125 truly was pregnant when she died.

Schweitzer and her colleagues approached the bone tissue from multiple avenues, re-examining the structure of the tissue with CT scans but also looking at its chemical composition. This is the key in teasing out tricky tissues, the researchers write, because medullary bone is chemically different from other bone types.

That’s because true medullary bone contains a higher proportion of mineral content and biomolecules called glycoaminoglycans than the surrounding tissue. So when the researchers used a stain to reveal the presence of biomolecules known to be abundant in medullary bone, the reaction fit with what they had suspected: the stain literally highlighted the fact that MOR 1125 had a femur infilled with the mineral-rich tissue.

Watch: Dinosaurs May Have Danced Like Birds. According to famed paleontologist Jack Horner, dinosaurs may have had courting behaviors similar to today’s birds.

The bone in MOR 1125 was not a pathology, and the superficially similar tissues in the pterosaurs must be attributable to some other condition or process. (Medullary bone is estrogen-dependent, Schweitzer and coauthors point out, so similar tissues in male and immature animals have to be something different.)

Pregnant dinosaurs really did lay down true medullary bone inside themselves, and this discovery holds fantastic possibilities for investigating how dinosaurs actually lived. But there’s a more subtle point that’s just as important to the way we think about these animals.

In fossiliferous shorthand, it’s easy to say that dinosaurs turned to rock during their long tenure in the earth. And yes, their bones and other tissues come down to us as permineralized versions of the originals. But it’s not as if everything of the real creatures was obliterated.

“Original organic components are assumed to be completely destroyed during burial and fossilization processes over millions of years,” Schweitzer and colleagues write. “However, we have shown that tissues, cells, and fragments of original molecules can persist across geological time.” Dinosaurs didn’t turn to stone like mythological trolls caught in sunlight. After all this time, tatters of the living creatures remain.

Look at dinosaurs as once-living animals, not piles of bone-shaped rocks, and you can start to see them.

References:

Schweitzer, M., Zheng, W., Zanno, L., Werning, S., Sugiyama, T. 2016. Chemistry supports the identification of gender-specific reproductive tissue in Tyrannosaurus rex. Scientific Reports. doi: 10.1038/srep23099

Schweitzer, M., Wittmeyer, J., Horner, J. 2005. Gender-specific reproductive tissue in ratites and Tyrannosaurus rex. Science. doi: 10.1126/science.1112158

Let’s Give Ceratosaurus a Hand

The large Ceratosaurus at the Natural History Museum of Utah. Photo by Brian Switek.
The large Ceratosaurus at the Natural History Museum of Utah. Photo by Brian Switek.

“What’s your favorite dinosaur?” I’ve come to hate this question. Not that it’s an unreasonable one. Much of my career has been built on the skeletal backs of dinosaurs and I really do adore them, but I honestly don’t have a strong favorite. I might as well be asked “What’s your favorite kind of burrito?” Any. All. I can’t pick a favorite.

I used to answer the dinosaur question with “Magpie.” And it’s true that I find the sassy little birds incredibly charming. I’m always happy to see them hopping around like little Velociraptors when I walk up to the Natural History Museum of Utah across town. I also know that this is usually a disappointment to whoever’s asking me, given they’re really talking about non-avian dinosaurs and don’t want me to reiterate the point that, yes, magpies and all other birds are living dinosaurs.

So rather than be a grump about the question, I’ve started to say “Ceratosaurus!” This, in public imagination, is more of a proper dinosaur. The Jurassic carnivore had exceptionally long fangs, a trio of horns on its face, and a row of bony armor along its spine, making it look appropriately fearsome.

Even if I hold back from calling it my all-time favorite, I really do have a soft spot for the pointy carnivore—so much so that I have the skeleton of a particularly-massive individual from Utah tattooed on my right arm and that I’m always excited to learn something new about this rare and still-mysterious carnivore. Case in point, I was genuinely excited to see paleontologists Matthew Carrano and Jonah Choiniere publish a new study on Ceratosaurus had bones that have been hidden for decades.

The skeleton from which Ceratosaurus was named – or most of it, anyway – was on display for over a century in the halls of the Smithsonian National Museum of Natural History. With the museum’s fossil halls undergoing a revamp, though, the old skeletons are being cleaned up and removed from their old constraints, including the Ceratosaurus that has been encased in a  plaster wall mount for so many years. And in doing this overdue cleanup, the Smithsonian’s preparators found bones that have gone unexamined since the dinosaur was put in plaster.

Most of what we know about the stubby arms of Ceratosaurus came from the articulated forearm and hand of the Smithsonian skeleton. They really are teeny compared to the dinosaur’s shoulder girdle and the rest of its body, even if it hasn’t received as much ridicule as T. rex for such proportions. In addition to the well-preserved left arm, though, the Smithsonian scientists found some elements of the right hand that were hidden away in the mount that once encased the body, which Carrano and Choiniere took as a jumping-off point to redescribe the arms of this Jurassic classic.

The lower left arm of Ceratosaurus as it was originally found. From Carrano and Choinire, 2016.
The lower left arm of Ceratosaurus as it was originally found. From Carrano and Choiniere, 2016.

While not as ridiculous as in later relatives such as Carnotaurus, the arms of Ceratosaurus were pretty stubby. Each hand had four short fingers with small claws on the tips that were not nearly as nasty-looking as the meathooks borne by its neighbors Allosaurus and Torvosaurus. Instead, the arms of Ceratosaurus were comparable to those of earlier, more distantly-related dinosaurs like Dilophosaurus, Carrano and Choiniere point out, albeit with shorter hands and small claws.

Ceratosaurus probably didn’t have a sharp mitt for catching or holding onto a prey, but an arm that fits with the trend overall trend towards a vestigial state seen in its relatives, the abelisaurs, over the following 84 million years.

This only highlights the fact that we don’t actually have a refined idea of how Ceratosaurus made its living during Morrison Formation time. Ceratosaurus was part of a trio of large Late Jurassic carnivores found in the same floodplain habitats, rarer than Allosaurus but not so rare as Torvosaurus. Is this a reflection of different habitat choices, or even varying feeding preferences?

Beyond that, did Ceratosaurus adopt an all-mouth hunting style like a hyena or wild dog, keeping those little arms tucked back while taking down baby sauropods and other prey with a razor-lined maw? We don’t yet know, but specimens like the one at the Smithsonian may hold additional clues. After all, a Ceratosaurus in the hand is worth two in the rock.

Reference:

Carrano, M., Choiniere, J. 2015. New information on the forearm and manus of Ceratosaurus nasicornis Marsh, 1884 (Dinosauria, Theropoda), with implications for theropod forelimb evolution. Journal of Vertebrate Paleontology. doi: 10.1080/02724634.2015.1054497

Paleo Profile: The Dragon Thief

Dracoraptor by Robert Nicholls.
Dracoraptor by Robert Nicholls.

The Triassic is often called the “dawn of the dinosaurs.” It’s an evocative image – a little dinosaur proudly strutting out onto a landscape to claim the world with tooth and claw – but we’ve got the timing wrong. As paleontologist Kevin Padian and others have made clear, dinosaurs were around during the Triassic but they were largely meek, marginal creatures. They didn’t rule anything. It took a mass extinction to remove much of the crocodile-line competition around 200 million years ago. The Jurassic was the true Dawn of the Dinosaurs, and a little carnivore from the cliffs of Wales offers a small window into that time.

Named Dracoraptor by David Martill and coauthors, the dinosaur was exposed by a cliff collapse that also threatened to destroy the remaining bones. The intact pieces were “‘rescue’ collected” by amateurs Nick and Rob Hanigan, and thankfully they donated the fossil to the Amgueddfa Cymru-National Museum of Wales.

Dracoraptor was a slender little thing, not much different from previously-described theropod dinosaurs from the Triassic such as Tawa and Daemonosaurus. But the critical difference is a matter of time. For reasons that remain a mystery to us, dinosaurs made it through the end-Triassic extinction virtually unscathed while the diverse and successful crocodile cousins – the pseudosuchians – were almost entirely stripped from the planet, leaving only the group that would eventually spawn crocodiles as we know them now. In short, dinosaurs got lucky. Dracoraptor embodies this dinosaurian hope that played out during the Jurassic and onward. The svelte predator couldn’t have conceived of it, but its kind would soon take over the terrestrial realm. It was the dragon of the dawn.

The known elements of Dracoraptor. From Martill et al., 2016.
The known elements of Dracoraptor. From Martill et al., 2016.

Fossil Facts

Name: Dracoraptor hanigani

Meaning: Dracoraptor, meaning “dragon thief”, is a reference to the mythical Dragon of Wales, while hanigani honors Nick and Rob Hanigan who discovered the skeleton.

Age: Around 200 million years old.

Where in the world?: Near Cardiff, south Wales.

What sort of critter?: A theropod dinosaur related to Tawa and Daemonosaurus.

Size: Approximately seven feet long.

How much of the creature’s body is known?: About 40% of a single skeleton including elements of the skull and body.

Reference: Martill, D., Vidovic, S., Howells, C., Nudds, J. 2016. The oldest Jurassic dinosaur: A basal neotheropod from the Hettangian of Great Britain. PLOS ONE. doi: 10.1371/journal.pone.0145713

Previous Paleo Profiles:

The Unfortunate Dragon
The Cross Lizard
The South China Lizard
Zhenyuan Sun’s dragon
The Fascinating Scrap
The Sloth Claw
The Hefty Kangaroo
Mathison’s Fox
Scar Face
The Rain-Maker Lizard
“Lightning Claw”
The Ancient Agama
The Hell-Hound
The Cutting Shears of Kimbeto Wash
The False Moose
“Miss Piggy” the Prehistoric Turtle
Mexico’s “Bird Mimic”
The Greatest Auk
Catalonia’s Little Ape
Pakistan’s Butterfly-Faced Beast
The Head of the Devil
Spain’s Megatoothed Croc
The Smoke Hill Bird
The Vereda Hilarco Beast
The North’s Sailback
Amidala’s Strange Horn
The Northern Mantis Shrimp
Spain’s High-Spined Herbviore
Wucaiwan’s Ornamented Horned Face
Alcide d’Orbigny’s Dawn Beast
The Shield Fortress

Paleontologists Discover Adorable Horned Dinosaur Baby

Art by Michael Skrepnick.
Art by Michael Skrepnick.

Dinosaur, roughly translated, means “terrible lizard.” The title works any way you look at it. Dinosaurs really were “terrible lizards” because they were about as unlizardlike as a reptile could possibly to be. Looking at it another way, the title encompasses the size, the teeth, and the apparent ferocity of our favorite dinosaurs. But it’s also a misleading moniker. Dinosaurs were not monsters. The non-avian species didn’t spend over 180 million years constantly stabbing, biting, and clawing each other. Tyrannosaurus was a terror and Stegosaurus was gnarly, yes, but there’s so much more to dinosaurs. For instance, some of them were downright cute.

In 2010, while looking for fossils along Alberta’s Red Deer River, paleontologists stumbled across part of a skull peeking out of the Cretaceous rock. Excavation revealed more and more bones, adding up to a nearly-complete skeleton, articulated and intact down to skin impressions on the ribs and the delicate ring of bones that were once encapsulated in the dinosaur’s eye. All cleaned up and now described by Phil Currie and colleagues, the dinosaur has turned out to be a baby Chasmosaurus – the smallest and most complete baby ceratopsid yet found.

A few pieces of the body went missing in the last 75 million years. The forelimbs and shoulders of the baby apparently fell into a sinkhole sometime before discovery, and the very tip of the tail broke off. But otherwise it’s a gorgeous for a dinosaur skeleton of any size, and drew audible gasps when Currie presented some initial photos to attendees of the annual Society of Vertebrate Paleontology meeting a few years back.

The baby Chasmosaurus. From Currie et al., 2016.
The baby Chasmosaurus. From Currie et al., 2016.

That the nearly five-foot-long skeleton is a from a baby, rather than a small species, is given away by various osteological details. Aside from the size, Currie and colleagues point out, the dinosaur has a bone texture typical of young, fast-growing animals, parts of the dinosaur’s vertebrae aren’t completely fused, it has a large orbit for its skull, and its frill had not yet grown the outer set of decorations called epiossifications, in addition to other traits. It all adds up to one unbearably adorable little dinosaur.

But there’s a greater paleontological reason for quantifying the cuteness. In the past paleontologists sometimes named baby ceratopsids as dwarf species, such as “Brachyceratops“. That risk is still there. When Currie and colleagues put all the baby Chasmosaurus traits into a program to figure out its relationships to other dinosaurs, the infant came out as a primitive ceratopsid. But when they tossed out all the characteristics known to change with age, the infant fell into its proper place with Chasmosaurus. In short, we need to know how dinosaurs changed with age in order to make sure we’re getting an accurate count of how many dinosaurs there actually were.

Currie and colleagues will continue to learn more about the baby dinosaur over the years. The new paper is just an initial description. And while it runs counter to a mature and staid appreciation of nature expected of science writers, I can’t help but look at the skeleton and artist Michael Skrepnick’s restoration and think “Aww.” The infant Chasmosaurus has the same big-eyed, short-faced look of a kitten and looks about as fierce as a puppy. Had non-avian dinosaurs survived to the present, and had evolution still allowed us to develop alongside them (which, hah!, not a chance), perhaps our Facebook pages and Twitter feeds would be filled with gifs of playful baby dinosaurs in addition to our mammalian companions.

Reference:

Currie, P., Holmes, R., Ryan, M., Coy, C. 2016. A juvenile chasmosaurine ceratopsid (Dinosauria, Ornithischia) from the Dinosaur Park Formation, Alberta, Canada. Journal of Vertebrate Paleontology. doi: 10.1080/02724634.2015.1048348

Paleo Profile: Wucaiwan’s Ornamented Horned Face

A restoration of Hualianceratops wucaiwanensis. Art by Portia Sloan Rollings.
A restoration of Hualianceratops wucaiwanensis. Art by Portia Sloan Rollings.

The ceratopsians are among our favorite dinosaurs. These great horned herbivores included Triceratops, Styracosaurus, and Pentaceratops in their ranks, as well as celebrated newcomers like Nasutoceratops. But these were only some of the largest and last of their kind. A new find, reported by paleontologist Genglu Han and colleagues, is a reminder that ceratopsians started off small.

The new dinosaur, found in the Late Jurassic rock of northwestern China, has been named Hualianceratops wucaiwanensis by the researchers. And while it looked relatively similar to another early horned dinosaur found in the same formation, Yinlong downsi, the skull pieces of Hualianceratops justify its identification as something different. And this has some important implications for the way horned dinosaurs evolved.

The new family tree of early ceratopsians proposed by Han and coauthors suggests that horned dinosaurs were undoing a rapid radiation right after they stepped onto the evolutionary stage. There were as many as five different ceratopsian lineages in the Late Jurassic, the paleontologists propose, setting the foundation for the evolution of later, better-known forms such as Psittacosuaurus, Protoceratops, and, of course, Triceratops and company.

Hualianceratops is therefore a part of an emerging view that the Late Jurassic was something of a proving ground for the sorts of dinosaurs that would rule the Late Cretaceous tens of millions of years later. Horned dinosaurs, tyrannosaurs, and ankylosaurs all got their start in the Late Jurassic, often as smaller and meeker-looking species than their more famous relatives. There wasn’t a wholesale shift between the Jurassic and Cretaceous worlds. As far as dinosaurs were concerned, the two menageries are connected by evolution, ecology, and time.

The reconstructed skullof Hualianceratops. Image by Han et al.
The reconstructed skull of Hualianceratops. Image by Han et al.

Fossil Facts

Name: Hualianceratops wucaiwanensis

Meaning: Hualianceratops means “ornamented horned face”, while wucaiwanensis refers to the area of China where the dinosaur was found.

Age: Between 162 and 159 million years old.

Where in the world?: Xinjiang, northwestern China.

What sort of critter?: An early ceratopsian, or horned dinosaur.

Size: The complete skull is estimated at 9.8 inches long. The whole dinosaur would have been slightly larger than Yinlong, another early horned dinosaur.

How much of the creature’s body is known?: A partial skull, lower jaw, left foot, and associated fragments.

Reference:

Han, F., Forster, C., Clark, J., Xu, X. 2015. A new taxon of basal ceratopsian from China and the early evolution of Ceratopsia. PLOS ONE. doi: 10.1371/journal.pone.0143369

Previous Paleo Profiles:

The Unfortunate Dragon
The Cross Lizard
The South China Lizard
Zhenyuan Sun’s dragon
The Fascinating Scrap
The Sloth Claw
The Hefty Kangaroo
Mathison’s Fox
Scar Face
The Rain-Maker Lizard
“Lightning Claw”
The Ancient Agama
The Hell-Hound
The Cutting Shears of Kimbeto Wash
The False Moose
“Miss Piggy” the Prehistoric Turtle
Mexico’s “Bird Mimic”
The Greatest Auk
Catalonia’s Little Ape
Pakistan’s Butterfly-Faced Beast
The Head of the Devil
Spain’s Megatoothed Croc
The Smoke Hill Bird
The Vereda Hilarco Beast
The North’s Sailback
Amidala’s Strange Horn
The Northern Mantis Shrimp
Spain’s High-Spined Herbviore

Paleo Profile: Spain’s High-Spined Herbivore

A restoration of the sail-backed dinosaur Morelladon. Art by Carlos de Miguel Chaves.
A restoration of the sail-backed dinosaur Morelladon. Art by Carlos de Miguel Chaves.

Sail backs were all the rage back in the Mesozoic. Some spinosaurs had them, with Spinosaurus itself bearing one of the most ornate of all, as well as the herbivorous Ouranosaurus, the shark-finned Concavenator, and the strange Deinocheirus, among others. And now, thanks to paleontologist José Miguel Gasulla and colleagues, another high-spined dinosaur has joined the club.

The Early Cretaceous herbivore, named Morelladon beltrani, didn’t have the most ornate ornament of the various sailbacks. The tall spines would have given it more of a high, narrow bump, superficially similar to the midline ridge of the carnivorous Acrocanthosaurus that was terrorizing North America around the same time.

What has continued to puzzle paleontologists, however, is why so many lineages of dinosaurs repeatedly evolved tall backs. No one knows for sure. The answer isn’t environmental, as high-spined dinosaurs lived in disparate habitats, and hot-running dinosaurs did not require sails to heat up, as early hypotheses supposed. The frontrunner right now is that they evolved for decoration, either to impress potential mates, intimidate rivals, or help members of the same species identify each other at a distance.

The latter possibility might be a good fit for Morelladon. During the Early Cretaceous, Gasulla and colleagues write, the Iberian Peninsula was home to a diverse group of dinosaurs that were variations on the theme of Iguanodon. They were so similar to each other that paleontologists have only just started to recognize how many different species and genera there were within a collection of bones that used to bear the Iguanodon title, and so it may be that the high spines of Morelladon helped the dinosaur stick with its own kind and avoid embarrassing encounters like approaching the wrong species come mating season.

The high spines of Morelladon. From Gasulla et al., 2015.
The high spines of Morelladon. From Gasulla et al., 2015.

Fossil Facts

Name: Morelladon beltrani

Meaning: Morelladon means “Morella tooth” in reference to the place the dinosaur was found, and beltrani honors Victor Beltrán “for his involvement and collaboration in the localization of the different fossil sites at the Mas de la Parreta Quarry.”

Age: Around 125 million years old.

Where in the world?: Castellón, eastern Spain.

What sort of critter?: An ornithopod dinosaur related to Iguanodon.

Size: About 20 feet long, similar to its relative Mantellisaurus.

How much of the creature’s body is known?: A tooth, six nearly-complete vertebrae and additional fragments of spine, the sacrum, most of the hips, a tibia, rib fragments, and two chevrons.

Reference:

Gasulla, J., Escaso, F., Narváez, I., Ortega, F., Sanz, J. 2015. A new sail-backed styracosternan (Dinosauria: Ornithopoda) from the Early Cretaceous of Morella, Spain. PLOS ONE. doi:10.1371/journal.pone.0144167

Previous Paleo Profiles:

The Unfortunate Dragon
The Cross Lizard
The South China Lizard
Zhenyuan Sun’s dragon
The Fascinating Scrap
The Sloth Claw
The Hefty Kangaroo
Mathison’s Fox
Scar Face
The Rain-Maker Lizard
“Lightning Claw”
The Ancient Agama
The Hell-Hound
The Cutting Shears of Kimbeto Wash
The False Moose
“Miss Piggy” the Prehistoric Turtle
Mexico’s “Bird Mimic”
The Greatest Auk
Catalonia’s Little Ape
Pakistan’s Butterfly-Faced Beast
The Head of the Devil
Spain’s Megatoothed Croc
The Smoke Hill Bird
The Vereda Hilarco Beast
The North’s Sailback
Amidala’s Strange Horn
The Northern Mantis Shrimp

Flexible Necks Made the Classic “Dinosaur Death Pose”

Spinosphorosaurus in the classic dinosaur death pose. From Remes et al., 2009.
Spinophorosaurus in the dinosaur death pose. From Remes et al., 2009.

Dinosaurs have lived on Earth for over 235 million years. That means they’ve also been dying for just as long. And when they die – whether we’re talking about a Parasaurolophus or a hummingbird – dinosaurs often take up a classic death pose. The head is thrown back over the body, sometimes almost touching the spine, and dinosaurs with long tails often have those balancing appendages curled upwards in an arc.

Paleontologists have been debating the cause of the dinosaur death pose for over a century now. There are two schools of thought on the subject. Some researchers have proposed that the contortion – technically called the opisthotonic posture – is caused at the time of death by poisoning, lack of oxygen to the brain, or similar circumstances that cause neck and tail to spasm into weird angles. Other paleontologists have suggested that the pose happens after death, with immersion in water or decay tensing muscles and ligaments that pull the head back and the tail up.

Both groups may be right. There seems to be a variety of ways for dinosaur skeletons to creak into the strangely-beautiful positions many of them are found in. But relatively little has been done to understand why dinosaurs and some of their prehistoric relatives, like pterosaurs, were even capable of such a pose. That’s what led biologists Anthony Russell and A.D. Bentley to X-ray a set of ten thawed, plucked chickens.

Chickens, like all birds, are dinosaurs, and they have the advantage of being readily available at the supermarket. So after thawing out their frozen birds, Russell and Bentley placed the birds in different opisthotonic positions starting at rest and moving the neck back until it mimicked what’s seen in fossil dinosaurs like the Struthiomimus on display at the American Museum of Natural History. They also checked to see if the birds’ heads could be flexed forward, beneath the body, and the researchers used the X-rays from both sets of trials to see how neck vertebrae angles changed with each position.

Chickens in varying degrees of opisthotonic posture. From Russell and Bentley, 2015.
Chickens in varying degrees of opisthotonic posture. From Russell and Bentley, 2015.

It actually didn’t take all that much for the birds to get to the dinosaur death pose. The posture, Russell and Bentley write, “can, in chickens at least, be facilitated simply through the limpness associated with death combined with the imposition of a relatively modest displacing force.” Getting the neck to arc downwards was something different altogether. The chickens’ necks locked when they were angled down and required significant force to keep them that way. The natural thing for a dinosaur neck to do, then, is to arc backwards.

The greatest changes happened in the middle of the neck. While the base and the very front of the chicken necks didn’t move much, Russell and Bentley found that two neck joints in the middle changed their orientations significantly and contributed the most to the pose. The flexibility of the skull helped, too. The spot where skull met neck stayed flexible in every position, and this undoubtedly helped some dinosaur skeletons achieve the posture where snout touches hip. This might also explain why many fossil dinosaur skeletons are found decapitated. Perhaps the anatomy that gives the skull a wide range of motion also allows it to easily be lost as soft tissues decay, letting heads roll as the rest of the skeleton is pulled towards becoming an osteological circle.

So while there’s probably an array of immediate causes for the dinosaur death pose, the ability for the saurians to take up the posture at all is because of flexible necks that can more easily be retracted back than pressed downwards. That’s the past of least resistance, literally, at or after the time of death, and why today’s dead chickens and emus look like they’re doing impressions of their fossilized predecessors.

Reference:

Russell, A., Bently, A. 2015. Opisthotonic head displacement in the domestic chikcen and its bearing on the ‘dead bird’ posture of non-avialan dinosaurs. Journal of Zoology. doi: 10.1111/jzo.12287

Paleo Profile: The Smoke Hill Bird

Photo by Brian Switek.
Hesperornis, restored at the New Mexico Museum of Nature and Science, was a cousin of the newly-named Fumicollis. Photo by Brian Switek.

During the late 19th century, as paleontologists were starting to uncover an array of prehistoric species that evolutionary theory predicted must have existed, ancient birds from the Cretaceous rock of Kansas became a scientific sensation. These were birds with teeth. The pair of them – dubbed Ichthyornis and Hesperornis by Yale’s Othniel Charles Marsh – underscored that birds evolved from toothy reptilian ancestors (which we now know were dinosaurs akin to Velociraptor).

Not that the archaic avians have always been popular. Upon seeing the government-funded monograph on the birds Marsh produced, penny-pinching congressmen turned “Birds with teeth!” as an incredulous cost-cutting rallying cry. And while the birds still show up in museums, they’re often overshadowed by their fuzzy non-avian relatives among the Dinosauria. Among a few others, however, paleontologists Alyssa Bell and Luis Chiappe have been taking a new look at these toothed birds, and, in fact, they’ve found a new one.

The new old bird, dubbed Fumicollis hoffmani by Bell and Chiappe, was one of these hesperornithiforms. These were loon-like diving birds that paddled through a now-vanished sea that washed over the midsection of North America. And, for a prehistoric bird, there’s actually quite a bit of Fumicollis to study. The vertebrae, hip pieces, and legs of the diver, originally excavated in 1937 and assigned to a different bird called Baptornis, allowed Bell and Chiappe to distinguish Fumicollis from other related birds.

All of a sudden the ancient environment preserved by the Smoky Hill Chalk is starting to look a little crowded. At least four different hesperornithiform birds, including Fumicollis, have been found in an upper section of the deposit that spans about five million years. That’s still a lot of time, and perhaps the birds were temporally separated. But what if they were actually ecological neighbors? If this were the case, Bell and Chiappe write, then the distribution of toothy diving birds through time and space might have been similar to what’s seen among modern penguins – a variety of species of different size classes could have partitioned the habitat, with some being deep divers and others foraging closer to the surface. If you were to plop into the waters of Kansas around 85 million years ago, and weren’t immediately eaten by a mosasaur, you may have been greeted by a diverse aviary of grinning birds.

The diversity of hesperornithiforms. From Bell and Chiappe, 2015.
The diversity of hesperornithiforms. From Bell and Chiappe, 2015.

Fossil Facts

Name: Fumicollis hoffmani

Meaning: Fumicollis is Latin for “smoke hill”, in reference to the Smoky Hill Member of the formation in which the bird was found, and the species name hoffmani honors museum donors Karen and Jim Hoffman.

Age: Around 85 million years old.

Where in the world?: Logan County, Kansas.

What sort of critter?: A toothed diving bird technically known as a hesperornithiform.

Size: About the size of a modern loon or grebe.

How much of the creature’s body is known?: Eight vertebrae, rib gragments, elements of the hips, parts of the right leg and foot, and a nearly-complete left leg.

Reference:

Bell, A., Chiappe, L. 2015. Identification of a new hesperornithiform from the Cretaceous Niobrara Chalk and implications for ecological diversity among early diving birds. PLOS ONE. doi: 10.1371/journal.pone.0141690

Previous Paleo Profiles:

The Unfortunate Dragon
The Cross Lizard
The South China Lizard
Zhenyuan Sun’s dragon
The Fascinating Scrap
The Sloth Claw
The Hefty Kangaroo
Mathison’s Fox
Scar Face
The Rain-Maker Lizard
“Lightning Claw”
The Ancient Agama
The Hell-Hound
The Cutting Shears of Kimbeto Wash
The False Moose
“Miss Piggy” the Prehistoric Turtle
Mexico’s “Bird Mimic”
The Greatest Auk
Catalonia’s Little Ape
Pakistan’s Butterfly-Faced Beast
The Head of the Devil
Spain’s Megatoothed Croc

Meet Marshosaurus, the Jurassic’s Forgotten Predator

Marshosaurus considers at Stegosaurus snack at the Natural History Museum of Utah. Photo by Brian Switek.
Marshosaurus considers a Stegosaurus snack at the Natural History Museum of Utah. Photo by Brian Switek.

I’ve spilled more than a little digital ink over the top carnivores of the Jurassic west. Allosaurus, Ceratosaurus, and Torvosaurus are all very dinosaur-y dinosaurs, checking the boxes for big, scary, and strange. But as I’ve poked around the Morrison Formation bones held at the Natural History Museum of Utah over the past few weeks, I realized I’ve done a disservice to ancient ecology by focusing on the flesh-rippers of the most imposing stature. There was an entire guild of Jurassic carnivores running around North America around 150 million years ago, and one of the least-known – at least to the public – is a mid-sized carnivore named Marshosaurus bicentesimus.

We know Marshosaurus was part of an wide array of predators, from tiny to giant, because of where it was found. The theropod’s bones were scattered through the jumble that is Utah’s Cleveland-Lloyd Dinosaur Quarry. Allosaurus totally dominates this site, but the bonebed has also yielded Ceratosaurus, Torvosaurus, a small tyrannosaur named Stokesosaurus, and, as Madsen, Jr. announced in 1976, Marshosaurus.

Madsen, Jr. made his case on a collection of hip bones and jaw elements that represented at least two individuals of 15-foot-long carnivorous dinosaur. That might not seem like much to go on, but the size and anatomy of Marshosaurus in comparison to its neighbors confirmed that the predator was something never before seen. This was a dinosaur that was larger than the sleek little Stokesosaurus but smaller than the biggest predators, more in the size range of a young subadult Allosaurus.

The trouble with Marshosaurus was that it was either a very rare dinosaur or it more regularly lived in environments away from the floodplains where so many of its neighbors became buried. Only a few pieces have been found at other sites, such as Dinosaur National Monument, and so most of the skeleton remains unknown. The features paleontologists have been able to spot on the assembled bones have narrowed the dinosaur’s identity down to some sort of megalosaur – a cousin of its larger competitor Torvosaurus – but, for the most part, Marshosaurus remains as much of a mystery now as it was in 1976.

In order to solve the puzzle, we need more puzzle pieces. And I’m hopeful that future fieldwork might do just that. This past summer, while I was scratching away at another site near the main bonebed, paleontologists and volunteers from the University of Wisconsin, Oshkosh moved tons of limestone to expose a fresh surface of the Cleveland-Lloyd Dinosaur Quarry. Every bone, every fragment is going to be carefully uncovered and documented when next summer raises the eastern Utah temperature to a setting fit for paleontology. If we’re lucky, more Marshosaurus might be waiting just below the surface.

Reference:

Madsen, J. 1976. A second new theropod dinosaur from the Late Jurassic of east central Utah. Utah Geology. 3 (1): 51-60

Did Dakotaraptor Really Face Off Against Tyrannosaurus?

Dakotaraptor pulls feathers from Ornithomimus it killed. Art by Emily Willoughby.
Dakotaraptor pulls feathers from Ornithomimus it killed. Art by Emily Willoughby.

By now you’ve probably heard about the giant “raptor” uncovered in South Dakota. The dinosaur’s discovery came as quite a shock. For the past century Tyrannosaurus rex has dominated our imaginations as the sole apex predator of the Hell Creek Formation, but Dakotaraptor steini, as Robert DePalma and coauthors dubbed the dinosaurs, was large enough to compete for flesh with young tyrannosaurs.

With scenes from the Jurassic Park franchise still stomping through our imaginations, it’s tempting to pit packs of 18-foot-long Dakotaraptor against the heavyweight champion T. rex, mobbing the bulky carnivore off its kills. DePalma has suggested as much, calling Dakotaraptor “the most lethal thing you can possibly throw into the Hell Creek ecosystem.”

But before we get too carried away and start commissioning murals of giant raptors slashing the flesh of Tyrannosaurus Age of Reptiles style, it’s worth thinking about what the world of dinosaurs was really like.

The known elements of Dakotaraptor and a reconstructed skeleton. From DePalma et al., 2015.
The known elements of Dakotaraptor and a reconstructed skeleton. From DePalma et al., 2015.

Dakotaraptor ups the diversity of dinosaurs known from the Hell Creek Formation. It’s an increase of one new species. And finding a new species means that there must have been a population of these big dromaeosaurids running around that paleontologists have missed up until now. (Although the idea of cooperative raptor packs rests on only the barest sliver of evidence right now.) But this doesn’t mean that where there was Tyrannosaurus, Dakotaraptor followed. What I’m getting at is a concept ecologists call species evenness.

Let’s take an avian dinosaur’s-eye view of the big Hell Creek Formation carnivores. We’ll cover Tyrannosaurus first. This dinosaur is known from about 50 partial-to-nearly-complete skeletons found in rocks between 68 and 66 million years old spanning Saskatchewan to New Mexico, at the very least. Dakotaraptor, on the other hand, is only known from a partial adult individual found near the top of the Hell Creek Formation in South Dakota and a smattering of other isolated elements from that area.

The fossil record is biased, of course. What’s preserved in the rocks is not a perfect record of life as it once was, and there are various other reasons why Dakotaraptor is so rare. Perhaps the dinosaur was the wrong size to be preserved as often as Tyrannosaurus. Maybe teeth and other pieces of this dinosaur were found before but could not be recognized as belonging to a giant raptor until now. Or the commercial fossil market could have snaffled up some of the relevant bones, making them inaccessible to paleontologists.

Future finds will inform what we know about the abundance and distribution of Dakotaraptor. But what if it took so long to find this predator because it truly was a rare animal with a relatively limited range? In terms of species evenness, in other words, the current spread of what we know is heavily imbalanced. Tyrannosaurus was extremely abundant and widespread while Dakotaraptor seems elusive, even by mid-size dinosaur standards.

This isn’t a knock against Dakotaraptor. Quite the opposite. If the dinosaur’s rarity isn’t stemming from a biased fossil record or a problem with sampling, then Dakotaraptor might eventually yield some new information about Hell Creek Formation ecology.

"Jane" is our best look at a juvenile T. rex. Photo by Brian Switek.
“Jane” is our best look at a juvenile T. rex. Photo by Brian Switek.

Up until now, Hell Creek Formation carnivores seemed to be widely split. There wasn’t a gradient from the small to the gargantuan as there was in the Late Jurassic Morrison Formation, but a wide gap between little nippers like Acheroraptor and the lone giant, Tyrannosaurus. What was in the middle, then, were juvenile Tyrannosaurus – lithe, leggy youngsters that had jaws better-suited to stripping flesh than to delivering crushing bites.

Dakotaraptor changes that picture. At least one other mid-sized predator was able to evolve and survive within the domain of Tyrannosaurus. Yet Dakotaraptor may have been so elusive because Tyrannosaurus still maintained a disproportionate presence on the landscape, or perhaps because Dakotaraptor typically lived in upland environments that weren’t preserved as often as the wet lowlands Tyrannosaurus frequented. So even though it’s possible, even probable, that Dakotaraptor and young Tyrannosaurus faced off over carcasses from time to time, it’s not as if Hell Creek Formation time was an era of constant shrieks, roars, and ruffled feathers.

Ceratosaurus was rare compared to Allosaurus. Photo by Brian Switek.
Ceratosaurus was rare compared to Allosaurus. Photo by Brian Switek.

This wouldn’t be the first time carnivorous dinosaur tallies have come out uneven. At the Late Jurassic Cleveland-Lloyd Dinosaur Quarry, for example, the remains of at least 48 Allosaurus have been uncovered while the same site has yielded only a single Ceratosaurus, a few Torvosaurus bones, and single-digit counts of the medium-sized carnivores Marshosaurus and Stokesosaurus. This pattern holds at a wider, rougher view, as well. Allosaurus was the most common large carnivore of the Morrison Formation with Ceratosaurus trailing behind in count and range, followed by even rarer and more restricted Torvosaurus, Stokesosaurus, and Marshosaurus. So, with a count of at least five, we can say that the upper part of the Morrison Formation had a diverse array of mid- to large-sized carnivorous dinosaurs, but that their numbers were not at all even.

Why different dinosaurs were unevenly spread in a given habitat or formation isn’t something that’s well-understood. It’s difficult to study an ecosystem that’s been dead for at least 66 million years. Answers could range from how we sample the fossil record to instances of niche partitioning like habitat preference or seeking particular food sources. There’s still plenty of rock to shift and dinosaurs to count. But if we’re ever going to fully understand dinosaurs, we need to step back from the carnivore vs. carnivore fights we used to imagine in the sandbox and try to understand them as animals that were each part of ever-shifting ecosystems. Dinosaurs weren’t monsters stalking around on unimportant backdrops. The endpoint of raising their bones in the first place is to envision how they fit into lost worlds.

Reference:

DePalma, R., Burnham, D, Martin, L., Larson, P., Bakker, R. 2015. The first giant raptor (Theropoda: Dromaeosauridae) from the Hell Creek Formation. Paleontological Contributions. doi: 10.17161/paleo.1808.18764