dinosaurs in their time

November 30, 2020 by wpengine

Mesozoic Monthly: Scipionyx

My high school calculus teacher, Mr. Surovchak, once told me about a competition he and his brother had every Thanksgiving. They would weigh themselves before and after dinner to indisputably measure who was able to eat the most. When it comes to dinosaurs, it’s typically much harder to tell what and how much they ate. However, a few fossils give us windows into the guts of dinosaurs – literally! Paleontologists are extremely thankful for spectacular fossils like that of Scipionyx samniticus, a small theropod dinosaur with several internal organs preserved!

Oil painting of *Scipionyx samniticus* in its Early Cretaceous environment by Emiliano Troco, used with permission. You can find more of their work on their Tumblr and contact them via their WordPress site.

Theropods, like Scipionyx, are dinosaurs that stand on two legs, usually with only three prominent toes on each hind foot. Some of the most famous dinosaurs are theropods, like Tyrannosaurus, Velociraptor, and previous Mesozoic Monthly honoree Citipati (does that make it famous? I like to think so). Most theropods interacted with the world primarily with their heads rather than their hands, hence why several of them look like they have oversized skulls and relatively underdeveloped forelimbs. Many also had hollow bones, and, as we can see in extremely well-preserved fossils, feathers. Is this all starting to sound familiar? That’s because these are also features of birds! If you’ve ever heard someone say that birds are dinosaurs, that’s because modern birds, which are called Aves or Neornithes, are just one evolutionary subset of theropod dinosaurs! Birds have all these features of theropod dinosaurs, plus others like toothless beaks and wings made partly from fused wrist and hand bones. If you are eating turkey for Thanksgiving dinner, remember that you’re eating a dinosaur!

Scipionyx didn’t look much like a turkey, though. It belonged to a group of theropods called compsognathids, which were long-tailed, slender, and relatively small predators. It wasn’t imposing size or an especially fascinating appearance that made Scipionyx special – it was the way the only known specimen was fossilized. It is so well preserved that many of its internal organs are intact in its body cavity! Petrified tissue from the trachea, small intestine, and even rectum can be seen in the fossil, as well as muscle tissue, blood vessels, and traces of other organs. We can tell from the bones and scales in its digestive tract that it ate several meals of lizards and fish before it died. There is such a wealth of biological information preserved in this single specimen, and we can learn even more when we consider its relatives. Although skin didn’t preserve in Scipionyx, at least one fossil of another compsognathid named Sinosauropteryx has such well-preserved skin and filament-like ‘protofeathers’ that we can even see pigments preserved! Based on Sinosauropteryx, we can assume that Scipionyx had some sort of filamentous or fuzzy covering as well, at least over some parts of its body.

The incredible fossil of *Scipionyx* preserves the dinosaur’s internal organs in 3D! For example, the sinuous shape of the small intestine is visible immediately behind the right elbow. Photo by *Giovanni Dall’Orto on Wikimedia Commons*. You can read more about this specimen in *a paper by Dal Sasso and Maganuco (2011).*

The fossil of Scipionyx is very small because the individual in question was just a hatchling when it died. Paleontologists can tell it was a hatchling, and not a small adult animal, because its proportions are similar to those of other juvenile dinosaur fossils and many of its bones had not yet fused together (you can learn more about how bones fuse as organisms get older in the Nemicolopterus edition of Mesozoic Monthly). The baby Scipionyx individual represented by the fossil would have measured around 18 inches (46 cm) long in life, and estimates based on how other compsognathids grew suggest that its species reached about 7 feet (2.1 meters) in length at adulthood. Not much is known about its habitat, but it was likely one of the largest animals around. Scipionyx was found in deposits laid down in a marine environment in what is now Italy. Back in the early part of the Cretaceous Period (the third and final division of the Mesozoic Era, or ‘Age of Dinosaurs’), when Scipionyx was alive, Italy was mostly under a shallow sea dotted with small islands, and the dinosaur would have lived on one of these. Since then, tectonic activity has dramatically changed the region, creating new mountains and lowering sea level to what it is today.

So, this Thanksgiving, if you’re looking for a conversation starter at the dinner table/family video call (or if you urgently need to divert discussion from a more sensitive topic), here’s an idea: ask your dining partners whether they think non-avian theropods like Scipionyx would have tasted more like turkey or chicken! Or, if your loved ones would rather learn than debate, you could perhaps offer to read them any of the 12 Mesozoic Monthly animal spotlights (that’s right, December makes one whole year of Mesozoic Monthly!). I’d certainly feel honored to make an appearance at your Thanksgiving feast.

Lindsay Kastroll is a volunteer and paleontology student working in the Section of Vertebrate Paleontology at Carnegie Museum of Natural History. Museum staff, volunteers, and interns are encouraged to blog about their unique experiences and knowledge gained from working at the museum.

Mesozoic Monthly: Gargoyleosaurus

Do you know what you’re going to dress up as for Halloween? This year, I’ll be going to work dressed as Velma Dinkley from Scooby-Doo. For the October edition of Mesozoic Monthly, I’ll be ‘unmasking’ a dinosaur with a monstrous name: Gargoyleosaurus parkpinorum, an armored dinosaur from the Jurassic Period!

Handy infographic of the ankylosaur *Gargoyleosaurus parkpinorum* showing its appearance, size, geographic and temporal occurrence, and more. Art by cisiopurple on DeviantArt, used with permission.

Gargoyleosaurus belongs to my favorite group of dinosaurs: the ankylosaurs! The group Ankylosauria is comprised of many big-bodied herbivores covered in osteoderms, which are pieces of bone embedded in the skin that act like armor. Their osteoderms came in many shapes and sizes, from tiny ossicles that protected their bellies, to large, fused pieces of bone that formed club-like structures on their tails. In most cases you can easily distinguish between the two major groups of ankylosaurs based on their style of osteoderms (though there are other features that distinguish them as well). Ankylosaurids are famous for their tail clubs: the last vertebrae in their tail overlap to form a rigid ‘handle’ that ends with a mass of fused osteoderms akin to a club. Nodosaurids, their sister group, sported massive osteoderm spikes on their shoulders instead of clubs on their tails. Some paleontologists distinguish a third group of ankylosaurs, called polacanthids, which have a rectangular ‘pelvic shield’ made of fused osteoderms that rests over the hips. There’s a lot of overlap between ‘nodosaurid’ and ‘polacanthid’ characteristics, though, so ankylosaurs with pelvic shields are typically grouped in with the nodosaurids instead of being recognized as their own group.

Conveniently, the Dinosaur Armor temporary exhibition at Carnegie Museum of Natural History features representatives of all three (or both, depending on your taxonomic preference!) ankylosaur subgroups: the ankylosaurid Akainacephalus, the nodosaurid Peloroplites, and the polacanthid (= nodosaurid?) Gastonia.

The imposing nodosaurid ankylosaur *Peloroplites* as seen in CMNH’s *Dinosaur Armor* exhibition. Check out those giant, spike-shaped shoulder osteoderms, a nodosaurid hallmark. Photo by Matt Lamanna.

There’s been some debate over where to place Gargoyleosaurus on the ankylosaur family tree because it displays a range of features from both major groups. It has pointy, horn-like osteoderms on the back of its head, which is a feature of ankylosaurids, but its skeleton lacks evidence of a tail club or other ankylosaurid characteristics. It also has a long snout, shoulder spines, and a pelvic shield, all features of nodosaurid (or polacanthid) ankylosaurs. The best explanation for the mix of features seen in Gargoyleosaurus is that it was one of the most basal nodosaurids, meaning it was one of the earliest nodosaurids to evolve and is therefore located at the base of the group’s evolutionary tree. If Gargoyleosaurus was a basal nodosaurid, that would explain why it still had features similar to those of ankylosaurids: because it had only recently evolved from the common ancestor of ankylosaurids and nodosaurids, not enough time had elapsed for features of that common ancestor (such as ankylosaurid-like skull osteoderms) to be removed by natural selection. This would be in keeping with the status of Gargoyleosaurus as one of the geologically oldest ankylosaurs of any kind discovered to date.

Albany County, Wyoming, ca. 150,000,000 B.P.: a solitary *Gargoyleosaurus* enjoys a shady spot by a stream in its Morrison Formation ecosystem. Art by Batavotyrannus on DeviantArt, used with permission.

No matter which ankylosaur subgroup Gargoyleosaurus belongs to, everyone can agree that it was a well-armored tank. Armor is a very useful defense against predators, since it generally covers the most vulnerable places on the body, such as the neck. Gargoyleosaurus lived in what is now the Morrison Formation, a famous set of rocks in the western US made of sediment deposited during the late Jurassic Period (the second of three periods in the Mesozoic Era, or Age of Dinosaurs). Most of the Jurassic dinosaurs on display at CMNH come from the Morrison Formation, such as our beloved long-necked sauropod Diplodocus, the even more massive sauropod Apatosaurus, and the forever popular Stegosaurus. But the Morrison ecosystem was home to a horde of formidable carnivores too—Allosaurus, Ceratosaurus, and Torvosaurus among them—so the armor of Gargoyleosaurus undoubtedly came in very handy. Contrary to what certain “Jurassic” franchises would lead you to believe, though, Tyrannosaurus rex did not live during the Jurassic Period, and so it never interacted with Gargoyleosaurus or any other members of the Morrison dinosaur community. That said, if trick-or-treating had been a possibility in the Jurassic, I’d imagine those inflatable T. rex Halloween costumes might have been very popular. Who doesn’t love those silly costumes?!

Mesozoic Monthly: Champsosaurus

Good news everyone: it’s September! We’ve made it to month nine of 12! Sometimes it feels like this year will never end. I take comfort in the idea that if life can survive the traumatic Cretaceous-Paleogene (K-Pg) extinction that killed the non-avian dinosaurs, I can make it through 2020. One of the survival champs of the K-Pg extinction was Champsosaurus, a superficially crocodile-like reptile belonging to the extinct group Choristodera.

The skeleton of *Champsosaurus laramiensis* looks superficially like that of a crocodilian, but this is the result of convergent evolution. Choristoderes (like *Champsosaurus*) and crocodilians lived contemporaneously for at least 150 million years, until the choristoderes said “after a while, crocodile!” and went extinct. Photo by Triebold Paleontology, Inc., used with permission.

The class Reptilia encompasses an incredible variety of animals: lizards, snakes, turtles, crocodilians, pterosaurs, dinosaurs, and even birds are just a few of its members. In addition to the familiar reptiles that live today, many other reptile groups thrived for millions of years before eventually going extinct. It’s easy to think of dinosaurs like Tyrannosaurus or Triceratops when we talk about extinct reptile groups, but in reality, many extinct groups of animals with no living relatives escape the public eye. Choristodera, an order within the class Reptilia, is one of these groups. Choristoderes were semi-aquatic or aquatic carnivorous reptiles that evolved during the Mesozoic Era (the Age of Dinosaurs) and died out in the Cenozoic Era (the Age of Mammals). Just because they went extinct does not mean they were unsuccessful; the group survived for at least 150 million years! Like many animals, a rapidly shifting environment was probably the source of their demise. Until that point, choristodere evolution was able to ‘keep up’ with the changing times, including the monumental global changes that came with the K-Pg extinction. The combination of a massive asteroid impact in what’s now Mexico, extensive volcanic activity in India, and worldwide climatic shifts resulted in the extinction of over 75% of all species. Research on choristodere teeth suggests that they beat the odds by adapting to new prey.

When you think of an aquatic carnivorous reptile, you probably think of a crocodilian – and that’d be right! The crocodilian body plan is a very successful build for hunting prey in the water. As another aquatic carnivorous reptile, Champsosaurus evolved similar traits. This is an example of convergent evolution, in which unrelated species develop similar characteristics to deal with comparable circumstances. (You can read about more examples of convergent evolution in the January edition of Mesozoic Monthly about the sauropodomorph dinosaur Ledumahadi.) Some of the shared features between Champsosaurus and crocodilians include long, muscular jaws for catching fish, eyes at the top of the head for peering out of the water, and a flattened tail that was paddled side-to-side for propulsion. Of course, Champsosaurus and the rest of the choristoderes had many features that set them apart as well. Unlike crocodilians, which have bony armor called osteoderms embedded in their skin, choristoderes just had skin covered with tiny scales. In addition, crocodilians have nostrils on top of their snouts so that they can breathe while lurking beneath the surface of the water; choristodere nostrils were at the end of their snouts, so that they could stick the tip of their nose out of the water like a snorkel and breathe from down below.

A right dentary (tooth-bearing lower jaw bone) of *Champsosaurus sp.* from the Upper Cretaceous of Wyoming in Carnegie Museum of Natural History’s Vertebrate Paleontology collection (specimen number CM 96509). The bone is facing upwards, so you’re looking down on the teeth. Check out the dark ‘stripes’ on the enamel of each tooth. These unusual enamel striations are a hallmark of neochoristoderes, the particular choristodere subgroup to which *Champsosaurus* belongs. Photo by Joe Sawchak.

The traits we see in the skeleton of Champsosaurus help paleontologists paint a picture of its behavior. Instead of lurking at the surface of the water, Champsosaurus would wait on the bottom of a shallow lake or stream for prey to come close, lifting the tip of its snout out of the water to breathe. When a tasty fish approached, it would spring off the bottom with its powerful legs and snatch it with its toothy jaws. Despite having strong legs, Champsosaurus was not adapted to a terrestrial lifestyle. In fact, adult males may not have been able to leave the water at all! Fossils attributed to females have more robust hips and hind limbs, allowing them to crawl onto land to lay eggs. According to this hypothesis, the less-robust males would have been restricted to an aquatic-only lifestyle.

Some of the freshwater environments that Champsosaurus inhabited were relatively cold, but that wasn’t a big deal; choristoderes may have been able to regulate their body temperature (a talent known as endothermy or ‘warm-bloodedness’). Crocodilians, by contrast, live in warm, tropical habitats because they are not capable of regulating their body temperature and rely on the sun to warm their bodies (aka ectothermy or ‘cold-bloodedness’). This would explain why choristoderes were able to live further north than crocodilians. However, it seems that crocodilians had the right idea; temperatures around the tropics change less during cooling and warming periods than those at higher latitudes. So, when the current Antarctic ice sheets began to form and the planet started cooling, the temperate choristoderes had to deal with more environmental change than the tropical crocodilians, and finally went extinct. I think the moral of the story is, we would all be handling 2020 better if we lived in the tropics!

In the Field: Following the Work of a Paleontologist

Introduction by Jessica Sperdute

Edited by Matt Lamanna

With 22 million specimens housed at Carnegie Museum of Natural History (CMNH) and nearly 10,000 on display at any given time, chances are you’ve seen a dinosaur or two during your museum visits. But have you ever wondered how those dinosaurs get to the museum after they’re found? Or how we know where to dig for them in the first place?

What is a Fossil?

Fossils are the remains of animals, plants, and other ancient life that have been preserved in rock layers, or sediment. Fossils can include things such as leaves, skin, feathers, hair, footprints, and, most commonly, hard material such as wood, shells, teeth, and bones. Even poop can be fossilized! Many kinds of fossils are rare, and studying them can help us understand how the world looked tens of thousands or even millions of years before our time. Scientists who study fossils are known as paleontologists.

Looking at the Layers

Paleontologists use many tools to help them find fossils, but the key to knowing where fossils may be hidden underground lies with rocks—massive layers of rocks, called strata, are piled onto one another over time. These layers of different rocks can tell us not only what type of rock the layer is made of, but also approximately how old the layer is. The study of rock layers is called stratigraphy, and paleontologists use it to find potential fossil beds. For instance, if a paleontologist is looking specifically for fossils of dinosaurs, they would use stratigraphy to locate exposed layers of sedimentary rocks that formed at the time when dinosaurs lived and died—the Mesozoic Era. Once rocks from the Mesozoic Era are found in a location, the paleontologist goes to that location to hunt for fossils.

Big Prospects

Finding the right type of strata is only half the work of finding fossils; once paleontologists arrive at the field site, they need to physically walk around and search for clues that fossils may be around or underneath them. This is called prospecting, and the best place to prospect is usually at the base of a hill. Wind and rain will erode or gradually wear away rocks, allowing some fossils to break loose from higher sediments and roll downhill. If a fossil fragment is found, the team can then search the area to see if there may be other, more complete fossils—oftentimes higher up the hill and still embedded in rock.

Once prospecting has yielded an area where a fossil is likely to buried, the team can begin to block out the site and start digging. They use a wide variety of tools—even household items like paintbrushes, shovels, and hammers—to uncover fossils without damaging them. Records are taken of this step-by-step process to ensure all the data, from the precise location of the dig site, to the type of fossils found and their spatial relationships to one another, and even the measurements of the quarry, is kept for further study.

Safety First

The team has found a fossil, dug it up, and recorded the data. Now what? Once a fossil has been carefully excavated, it needs to be protected. Most fossils are delicate, so to transport them, especially larger ones, paleontologists use a method called plaster jacketing to protect them. First, they wrap the fossil in soft material such as paper towels, toilet paper, or aluminum foil to cover it. Then they wrap the covered fossil in strips of burlap that have been soaked in liquid plaster. This method is like using a cast on broken bones. After the plaster hardens, it acts as a shield. When the fossil has been safely transported and is ready to be studied or put on display at a place like Carnegie Museum, the paleontologist can gently cut away the plaster without damaging the fossil inside.

Paleontologist Photos

Dr. Matt Lamanna, Mary R. Dawson Associate Curator of Vertebrate Paleontology here at CMNH, has shared some of his favorite photos of his work at previous fossil dig sites. Look at the photos—do you recognize some of the locations, the tools that Dr. Lamanna is using, or the fossils that he’s digging up?

Here, Carnegie Museum of Natural History Mary R. Dawson Associate Curator of Vertebrate Paleontology Dr. Matt Lamanna is pointing at two ribs of a small—possibly baby—sauropod (long-necked plant-eating dinosaur) projecting from a rock face in the Bahariya Oasis of Egypt in 2001. He’d found this small sauropod only minutes before this photo was taken. Sometimes prospecting yields great finds! Credit: Mandi Lyon.

Dr. Matt Lamanna (right) on an expedition that found dozens of roughly 120-million-year-old fossil bird skeletons, mostly belonging to the species *Gansus yumenensis*, in the Changma Basin of Gansu Province, China in 2004. Lamanna is with collaborator Hailu You. Credit: Ken Lacovara.

In this photo, also taken in 2004 in Gansu Province, China, Dr. Lamanna poses next to the ribs of a giant sauropod—these ribs were just part of the massive skeleton that was discovered. Credit: Hailu You.

Dr. Lamanna on the expedition that found the new and gigantic titanosaur (a type of sauropod, again, a long-necked plant-eating dinosaur) *Dreadnoughtus schrani* in Santa Cruz Province, Argentina in 2005. Lamanna is shoveling loose rock out of the Dreadnoughtus quarry. Credit: Ken Lacovara.

Members of the expedition from Drexel University, the Universidad Nacional de la Patagonia San Juan Bosco, and CMNH that found the giant titanosaur *Dreadnoughtus* in Santa Cruz Province, Argentina in 2005 (left to right: Lucio Ibiricu, Chris Coughenour, Ken Lacovara, Matt Lamanna, Marcelo Luna, and Gabriel Casal). The huge femur (thigh bone) and tibia (shin bone) of *Dreadnoughtus* are visible in the foreground. Credit: Matt Lamanna.

Dr. Lamanna on the expedition that found the titanosaur *Dreadnoughtus* in Santa Cruz Province, Argentina in 2005. He’s sitting behind the 1.91 m (6 ft 3 in) femur, or thigh bone, of *Dreadnoughtus* not long after its discovery. Credit: Chris Coughenour.

Here, Dr. Lamanna is using a rock drill (one of his very favorite field tools!) to help collect the skeleton of a new armored dinosaur in Queensland, Australia in 2008. Credit: Steve Salisbury.

Dr. Lamanna (right) with collaborator Gabriel Casal making a plaster-and-burlap jacket to protect bones of the titanosaur *Sarmientosaurus musacchioi* in Chubut Province, Argentina in 2008. Credit: Mandi Lyon.

Lamanna on the day he found the only known fossil of the new, ~90-million-year-old crab *Hadrocarcinus tectilacus* on James Ross Island, Antarctica in 2009. Credit: Patrick O’Connor.

Here’s another photo of Lamanna on James Ross Island of Antarctica, this time in 2011. The team found tooth and bone fragments of the theropod—meat-eating dinosaur—*Imperobator antarcticus* at this site. Credit: Meng Jin.

During the 2011 Antarctic expedition, Lamanna and his fellow paleontologists also found lots of fossils on nearby Vega Island, especially those of approximately 70-million-year-old birds. Credit: Meng Jin.

In this photo from 2015, Lamanna is shown collecting fossils in a New Jersey quarry with a research team from Drexel University, who were uncovering marine creatures from the very end of the Mesozoic Era. Credit: Ken Lacovara.

Jessica Sperdute is a Gallery Presenter II Floor Captain and Lead Animal Husbandry Specialist in CMNH’s Lifelong Learning Department. Museum staff, volunteers, and interns are encouraged to blog about their unique experiences and knowledge gained from working at the museum.

The Strange Saga of Spinosaurus, the Semiaquatic Dinosaurian Superpredator

I’ve been captivated by dinosaurs for as long as I can remember. My parents tell me that I told them that I wanted to be a paleontologist as early as age four. Naturally, then, I had lots and lots of books about dinosaurs when I was a boy growing up during the 1980s. One of the dinosaurs that always fascinated me the most was Spinosaurus aegyptiacus. Found in 1912 in the Bahariya Oasis of the Western Desert of Egypt (could anyplace sound more exotic to a small-town kid from upstate New York?!), Spinosaurus was originally known from a highly incomplete but also very large and extremely distinctive partial skeleton found in a middle Cretaceous-aged (roughly 95-million-year-old) rock layer in the oasis. Among the few skeletal elements known were part of a strangely shaped (for a dinosaur) lower jaw, some crocodile-like teeth, and most strikingly, several back vertebrae that each sported tall spines, some of them measuring nearly six feet. These spines clearly impressed Ernst Stromer von Reichenbach, the German paleontologist who studied the skeleton and gave the animal its name in a 1915 publication. Tragically, however, that original Spinosaurus skeleton—and all of Stromer’s other dinosaur fossils from Egypt—were destroyed during the Second World War, more specifically in a British Royal Air Force bombing of Munich on April 24, 1944. The story of Stromer’s lost dinosaurs found its way into many a children’s book, including several that I read cover-to-cover. As such, the tale took on near-legendary status for me, and, I’m sure, many other young dinosaur enthusiasts around the world. Here was an absolutely extraordinary dinosaur from a faraway land, similar in size to the gargantuan Tyrannosaurus rex, but clearly very different from all other predatory dinosaurs known at the time – and it was represented only by a few teeth and bones that had been blasted into oblivion decades ago and so now existed only as pictures in books.

A scan of my photocopy of plate I of Ernst Stromer’s original 1915 publication on *Spinosaurus aegyptiacus*, showing some of the teeth and bones preserved in the holotype (= name-bearing) partial skeleton, discovered in 1912 in Egypt’s Bahariya Oasis. Check out the long spines on the back vertebrae at lower left!

Stromer’s conception of *Spinosaurus*, as depicted in a 1936 publication and on a glass slide of his that colleagues of mine scanned during our visit to the Paläontologisches Museum München in Munich, Germany in 2001. Stromer knew this animal was big, as evidenced by the human skeleton he included for scale. Interestingly, too, he reconstructed *Spinosaurus* with unusual proportions for a carnivorous dinosaur, such as an abnormally elongate torso and short hind limbs. We’ll come back to those odd proportions a little later…

When I arrived in graduate school at the University of Pennsylvania in 1997, one of the first things I did was make a lengthy list of all the paleontological sites I was interested in exploring, ranked by their potential (in my mind, at least) to produce scientifically significant finds. The Bahariya Oasis and the search for a ‘replacement Spinosaurus’ quickly rose to the top of the list. Amazingly, no one had ever found—or at least officially reported—new dinosaur fossils in the oasis in the more than half-century since Stromer’s beasts were obliterated during that fateful airstrike. A need to keep this post to a reasonable length prevents me from describing the stars that had to align to make this happen, but in January 2000 I found myself in the Bahariya Oasis—one of the places I’d dreamed about going since I was a small child—as part of the first significant ‘dinosaur hunt’ to take place at the site since the early 20^th century. It was bittersweet, though, in the sense that we never really found that ‘replacement Spinosaurus’ I’d fantasized about – all we ever discovered of that creature were a few isolated, fragmentary teeth and bones (and, in a very different location, a couple previously unpublished photos of the original skeleton in a Munich archive). We did find and dig up a gigantic new species of long-necked, plant-eating sauropod dinosaur, Paralititan stromeri, a creature that to this day is one of the largest land animals of any kind that’s ever been found, anywhere – but that’s another story for another time.

One of the rare contributions that I personally have made to scientific knowledge of *Spinosaurus*: a glass slide showing the only known photo of the right dentary (tooth-bearing lower jaw bone) of the original, name-bearing partial skeleton from Egypt. Like all of Stromer’s Egyptian dinosaur material, this specimen (including this bone) was destroyed in a British air raid on Munich during World War II. Several colleagues and I ‘rediscovered’ this photo—which nobody apparently knew existed—in an archive at the Paläontologisches Museum München in 2001. We published it and one other previously unknown photo of the Spinosaurus type specimen in a 2006 paper in the Journal of Paleontology.

A much younger yours truly digging up the incomplete left humerus (upper arm bone) of the gigantic sauropod (long-necked herbivorous dinosaur) *Paralititan stromeri* in the Bahariya Oasis of Egypt, February 2000. *Paralititan* is one of the largest dinosaurs ever discovered – a nice ‘consolation prize’ given that we didn’t find much of *Spinosaurus* during our expeditions to Bahariya. (A cast replica of the complete right humerus of *Paralititan* is on display in *PaleoLab* at Carnegie Museum of Natural History.) Credit: Josh Smith.

Back to the matter at hand, meaning Spinosaurus. Fast-forward to 2011. I had the honor of serving as the external thesis examiner for Nizar Ibrahim, a promising doctoral student at University College Dublin in Ireland. I’d known Nizar for years, ever since he reached out to me by email while an undergraduate at the University of Bristol, England, to discuss our mutual interests in African Cretaceous dinosaurs. Nizar’s Ph.D. thesis was on dinosaurs and other middle Cretaceous-aged vertebrates from the celebrated Kem Kem beds of southeastern Morocco, a set of rocks that had yielded a fossil fauna very similar to, though seemingly more diverse than, that of the Bahariya Oasis. Among the many finds that Nizar documented in his colossal thesis were intriguing new remains of Spinosaurus. I went to Dublin to participate in his successful thesis defense, and afterward, he and I hit up some of the city’s finest public houses to celebrate (no surprise for those who know me). Over a pitcher of yummy Irish stout, he told me an exciting story – he and his team had lately discovered not just isolated bones of Spinosaurus in Morocco, but parts of a probable new skeleton. If so, this find would be the first skeleton since Stromer, and moreover would be exceedingly important given how little was known about Spinosaurus, even as recently as the early 2010s. The more parts we paleontologists have of a given fossil animal, the more we can generally learn about it, so the prospect of a new and relatively complete Spinosaurus skeleton—in other words, many bones belonging to a single individual dinosaur—was thrilling to say the least.

Again I’ll skip details for brevity’s sake, but fast-forward once again, to 2014. I was contacted by an editor of Science—one of the foremost scientific journals in the world—to peer-review a paper that had been submitted by (you guessed it!) Nizar and a long list of collaborators describing that new skeleton of Spinosaurus that he’d told me about over beers in Ireland three years before. Nizar and team had revisited the quarry and it had panned out in a big way. From this one, single individual Spinosaurus—again, the first associated skeleton of this dinosaur to have been found in roughly a century—they had bones from the skull, backbone (including a few of those famously long-spined vertebrae!), forelimb, pelvis, and hind limb. More importantly, these ‘new’ bones revealed that Spinosaurus was even more bizarre than anyone imagined! We already knew, from Stromer’s specimen and other, isolated finds made through the years, that the shapes of the skull and back were really weird for a predatory dinosaur. Now, the new skeleton showed that the bones were remarkably dense, the hind legs were oddly short, and the hind feet may have been webbed! All of this led Nizar and colleagues to propose that Spinosaurus may have been semiaquatic; in other words, that its lifestyle was much more comparable to that of a modern-day alligator or crocodile than it was to a more ‘typical’ land-living predatory dinosaur such as T. rex. Other evidence for an affinity to watery habitats had been found in Spinosaurus and closely related dinosaurs (known, perhaps unsurprisingly, as spinosaurids) before, but this was, in my mind, the most convincing case yet made that these animals spent significant amounts of their time at least partly submerged in lakes and rivers. The paper was published in Science a few months later, accompanied by a cover story in National Geographic magazine and a special on the venerable PBS TV series NOVA. Almost exactly one hundred years after it had been named, Spinosaurus had become a celebrity.

Nizar Ibrahim and colleagues’ initial conception of *Spinosaurus aegyptiacus* in the flesh, released to coincide with the publication of their *Science* paper in 2014. Two aspects stand out: as Stromer already knew (see his skeletal reconstruction above), the animal is enormous, but it was more oddly proportioned than even he had imagined. Note also the ‘regular-looking’ (for a dinosaur) tail, and read on. Credit: Davide Bonadonna.

Semiaquatic *Spinosaurus* chowing down on a tasty lungfish in what is now northern Africa some 95 million years ago. Italian paleoartist Davide Bonadonna has produced some of the most beautiful and accurate modern depictions of this extraordinary dinosaur, and I’m grateful to him for letting me reproduce his art here.

But the story didn’t end there. Some prominent paleontologists criticized Nizar and colleagues’ semiaquatic interpretation of Spinosaurus. These opinions weren’t a final judgment. Instead, this is just how science works: we scientists propose ideas, or hypotheses—in this case, that Spinosaurus lived and behaved more like a crocodile than your garden-variety carnivorous dinosaur—and then test these hypotheses by reevaluating the existing evidence and/or bringing new information to light. If a hypothesis repeatedly stands up to testing, then it gradually gets incorporated into the body of knowledge. Other paleontologists presented evidence that they claimed refuted the semiaquatic hypothesis, but Nizar and team eventually countered with new data of their own. In late 2019, another prominent scientific journal—this time it was Nature—came calling, asking me to review a second paper by Nizar et al. on Spinosaurus. What, I thought, could these researchers have to say about this dinosaur that they hadn’t already said before? Well, as it turns out, Nizar and colleagues had kept digging at their Spinosaurus skeleton site, and incredibly, they’d continued to find important new bones belonging to the same specimen. Among these post-2014 finds was the almost complete tail. When I saw what it looked like (via an illustration in their paper), I literally laughed out loud with surprise and delight. Somehow, the shape of the Spinosaurus tail Nizar’s team had discovered—the first even reasonably complete tail of this dinosaur to have ever been unearthed—was simultaneously both unexpected and predictable. It looked really dissimilar from the tails of other predatory dinosaurs, but it was nearly exactly like what one might expect for a dinosaur that used its tail to propel itself through water. In other words, the tall, fin-like tail of Spinosaurus looked more like that of a supersized alligator or newt than that of T. rex.

Nizar and team’s Nature paper on their Spinosaurus tail was published this past April 29. Is it the last word on this dinosaur and its mode of life? Most certainly not, but the evidence is now stronger than ever—in my opinion, very strong—that Spinosaurus spent more time in the water than any other non-avian (= non-bird) dinosaur that we currently know about.

The modern view of *Spinosaurus*, not as a ‘regular’ predatory dinosaur, but rather as a specialized semiaquatic hunter that spent much of its life in the water. Self-serving side note: the three smaller, spiky-looking fish are *Bawitius bartheli*, a polypterid (an archaic, still-extant group of thick-scaled ray-finned fishes) that several colleagues and I named in 2012 from fossils found in the Bahariya Oasis. The larger fish at lower left is the giant coelacanth *Axelrodichthys* (sometimes called *Mawsonia*) *libyca*. Credit: Davide Bonadonna.

Two *Spinosaurus* invite the sawfish *Onchopristis numidus* to lunch in what’s now northern Africa some 95 million years ago. Look at those fin-like *Spinosaurus* tails! Credit: Davide Bonadonna/National Geographic.

Nizar (who’s a Research Associate here at Carnegie Museum of Natural History), myself, and our many colleagues and collaborators are continuing to study the mysterious dinosaurs and other fossil vertebrates from the middle and Late Cretaceous of northern Africa. Indeed, Nizar and I have several collaborative papers in the works right now, and I’m also working with an amazing team of paleontologists at Mansoura University on multiple new Egyptian fossil finds. It’s a good bet that African Cretaceous dinosaurs even stranger than Spinosaurus are still out there, waiting to be discovered!

Further reading/watching:

Nothdurft, W. E., with J. B. Smith, M. C. Lamanna, K. J. Lacovara, J. C. Poole, and J. R. Smith. 2002. The Lost Dinosaurs of Egypt. Random House, New York, 256 pp.

Smith, J. B., M. C. Lamanna, H. Mayr, and K. J. Lacovara. 2006. New information regarding the holotype of Spinosaurus aegyptiacus Stromer, 1915. Journal of Paleontology 80:400–406.

Ibrahim, N., P. C. Sereno, C. Dal Sasso, S. Maganuco, M. Fabbri, D. M. Martill, S. Zouhri, N. Myhrvold, and D. A. Iurino. 2014. Semiaquatic adaptations in a giant predatory dinosaur. Science 345:1613–1616.

Bigger Than T. rex (NOVA documentary): https://www.pbs.org/wgbh/nova/video/bigger-than-t-rex/

Henderson, D. M. 2018. A buoyancy, balance and stability challenge to the hypothesis of a semi-aquatic Spinosaurus Stromer, 1915 (Dinosauria: Theropoda). PeerJ 6:e5409.

Ibrahim, N., S. Maganuco, C. Dal Sasso, M. Fabbri, M. Auditore, G. Bindellini, D. M. Martill, S. Zouhri, D. A. Mattarelli, D. M. Unwin, J. Wiemann, D. Bonadonna, A. Amane, J. Jakubczak, U. Joger, G. V. Lauder, and S.E. Pierce. 2020. Tail-propelled aquatic locomotion in a theropod dinosaur. Nature 581:67–70.

Matt Lamanna is Mary R. Dawson Associate Curator and Head of the Section of Vertebrate Paleontology at Carnegie Museum of Natural History. Museum staff, volunteers, and interns are encouraged to blog about their unique experiences and knowledge gained from working at the museum.

Mesozoic Monthly: Gryposaurus

The Late Cretaceous-aged (~75 million-year-old) large-nosed North American hadrosaur (aka duck-billed dinosaur) *Gryposaurus* by ginjaraptor on DeviantArt.

Anyone who frequents the Pittsburgh area is familiar with ‘Pittsburghese,’ the regional dialect given full voice in what was once voted America’s ugliest accent (a fact that does not diminish our pride for it). One of my personal favorite Pittsburghese words is “nebby,” which translates to “nosy” for any non-local readers. “Nebby” can be used in a variety of contexts: the distant relative asking prying questions about your love life at Thanksgiving dinner is nebby, the pet cat trying to crawl under the bathroom door to see what you’re doing is nebby, and even the statue of Carnegie Museum of Natural History mascot Dippy the Diplodocus, silently judging your driving on Forbes Avenue, is nebby. We can assume other dinosaurs were nebby too, since so many had huge noses to stick into things. One of the biggest noses in the fossil record belongs to Gryposaurus notabilis, the star of this edition of Mesozoic Monthly.

Gryposaurus belongs to a group of dinosaurs called hadrosaurs, which are commonly referred to as duck-billed dinosaurs. Hadrosaurs were herbivores that got their nickname from the flat, toothless, somewhat duck-like beaks at the tips of their jaws. These beaks were used to bite through tough vegetation so that it could be ground up by the numerous teeth embedded in the rear half of the jaws. There are two main groups of hadrosaurs, both of which are featured in CMNH’s Dinosaurs in Their Time exhibition. Probably the more famous group is the Lambeosaurinae, known for their distinctive head crests that housed extra-long nasal passages. Virtually everyone can recognize the incredible backward-curving crest of Parasaurolophus (featured multiple times in the Jurassic Park franchise), and visitors to CMNH will also know the helmet-like crest of Corythosaurus. The second group is the Saurolophinae (traditionally known as the Hadrosaurinae), which typically lack bony crests. You can find a simulated carcass of the saurolophine Edmontosaurus (lovingly known to those of us in CMNH’s Section of Vertebrate Paleontology as “Dead Ed”) between the two imposing Tyrannosaurus skeletons in Dinosaurs in Their Time.

A gallery of hadrosaur heads. Top left: the lambeosaurine *Parasaurolophus* at the Field Museum of Natural History in Chicago (photo by the author). Top right: the lambeosaurine *Corythosaurus* at Carnegie Museum of Natural History (photo from Wikimedia Commons). Bottom left: the saurolophine *Edmontosaurus* at the Houston Museum of Natural Science (photo from Wikimedia Commons). Bottom right: the saurolophine *Gryposaurus* at the Natural History Museum of Utah in Salt Lake City (photo from Wikimedia Commons).

As a crestless hadrosaur, Gryposaurus was a saurolophine. Despite its lack of crest, its skull still had pizzazz: its nasal bone arched dramatically, giving the impression of a ‘Roman nose’ (which is very noticeable if you compare the skulls of Edmontosaurus and Gryposaurus in the image above). The name Gryposaurus notabilis means “notable hooked-nose lizard” in homage to this feature. G. notabilis is the type species of Gryposaurus; type species are typically the first ones to be named in a genus, and therefore become the reference to which all new specimens that may belong to that genus are compared. The other species (such as G. monumentensis, shown in the photo montage above) are similar enough to the type species that they can be referred to the genus Gryposaurus, but they differ in too many ways to be assigned to G. notabilis itself.

Occasionally, paleontologists will revisit a fossil species or genus and decide that it is either too similar to another to justify its own name or that certain specimens are too different to be grouped under the same name. Kritosaurus, another saurolophine with a ‘Roman nose,’ has fallen victim to both of these circumstances. It was originally considered its own genus, but was subsequently revisited by paleontologists who decided that it was so similar to Gryposaurus that the two genera were lumped together under the name Gryposaurus (when combining taxonomic groups, the first name that was published is the one that gets used). However, later paleontologists reviewed the evidence again and split a single species of Kritosaurus back out of Gryposaurus. The famous sauropod (giant long-necked herbivorous dinosaur) Brontosaurus underwent a similar series of changes over the years: originally, it and Apatosaurus were considered different animals, but after a review they were lumped together under Apatosaurus. Recently, the two were split apart again and the name Brontosaurus was revived (to the delight of fans of that name around the world).

It is not uncommon in paleontology for species to be lumped or split based on new or revisited evidence. When you consider that the decision to name new fossil species is often based on fragmentary, highly incomplete skeletons, you can see why it might be difficult to get things right the first time! These changes sometimes give people the impression that paleontologists “can’t make up their minds” or “contradict themselves,” but we must remember two things. First, that science is meant to change based on new evidence. Second, there have been thousands of paleontologists over the course of history, and every one of them is an individual person who can draw their own conclusions based on the same evidence. Although the resulting changes can disappoint fans of a specific animal or hypothesis, revision is normal and beneficial for the field as a whole. Scientists are supposed to be nebby – it’s how we make new discoveries!

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