After a long day in the woods, the diminishing sun beat down on our shoulders. We laboured over shovels and dug with our bare hands to remove the sand, tired. We were researching in the center of the Navajo Nation, in the center of dinosaur country on the Colorado Plateau of northern Arizona, to ascertain the ages of two skeletons of Dilophosaurus wetherilli had already been discovered there previously. We’d spend a hot June day in 2014 hiking up and down the badlands, measuring the rock beds, and collecting geologic tests in our backpacks. And now we had to dig up something—not a new fossil, but our tractor, which had been stuck in the sand dunes and was buried up to the axles. Rather than the swashbuckling of the film, the life of a globe-trotting research scientist is embedded in the mundane—applying for permissions, writing notes, preparing meals, and washing the dishes in camp, analyzing the day’s data by the light of the campfire.
We never see Indiana Jones or Alan Grant pulling a tractor out of a ditch. Dinosaurs and paleontologists burst into movie screens all over the world in the summer of 1993. Based on the 1990 Michael Crichton book, Jurassic Park turned many little-known creatures into instant stars and villains. Velociraptor and Dilophosaurus were added to the public lexicon alongside Tyrannosaurus and Triceratops. In most action movies, the dinosaurs are not creatures that biologists are familiar with from nature. Yet it was the Jurassic Park franchise’s storyline dependence on state-of-the-art paleontology and genes that made it so famous (it shattered box office records in 1993 and hit the charts again in the summer of 2020).
For the first time, author Crichton and director Steven Spielberg gave viewers a new glimpse at dinosaur science, and the picture they painted of alive, intelligent creatures still resonates today. Naturally, Crichton and Spielberg took artistic license to tell a convincing narrative, dramatizing both the scientists and the dinosaurs. Dilophosaurus was the specimen that deviated the most from the fossil data. It takes the shape of a golden retriever–sized beast with a rattling frill and venomous spit in the film, and it kills Dennis Nedry, a computer programmer turned dinosaur embryo smuggler.
What was it like to be Dilophosaurus? When this animal first became famous, scientists didn’t have a complete picture of it. Researchers also discovered significant new fossil fossils of Dilophosaurus. They studied all bones using more advanced techniques in almost three decades since the dinosaur was given the Hollywood treatment. As a result, we can now recreate this dinosaur in great detail, including its anatomy and behavior, how it formed, and the environment it lived in. The results reveal that the actual Dilophosaurus bears no similarity to the movie Dilophosaurus. They also have the most accurate portrait of an Early Jurassic dinosaur to date.
A STAR IS BORN
Today, Dilophosaurus is known as a bipedal, meat-eating dinosaur with two parallel ridges of fragile bone along with the crown of the head (its name comes from the Greek words for “two-crested reptile”). When Samuel Welles, a paleontologist at the University of California, Berkeley, published his thesis on two skeletons discovered by Jesse Williams, a Navajo person who lived near Tuba City, Ariz., in a series of articles in 1954, the species had a different identity.
Welles named the beast Megalosaurus Wetherill, assuming it to be a new species in the previously recognized genus Megalosaurus since the crest had not been found among the fragmentary remnants. Welles learned that the initial discovery represented a different species after discovering another species in 1964 that retained the peak of the skull with its double crests, so he called the animal Dilophosaurus wetherilli.
Welles’ 1984 anatomical analysis and sculpted reconstructions of the bones in museum collections, as well as artwork by palaeontologist Gregory Paul in the 1988 book Predatory Dinosaurs of the World, were used to create the basic body plan of the dinosaur in Jurassic Park. However, in some main details, the Jurassic Park Dilophosaurus differed from the scientific records of the time. The venomous secretion and collapsible frill of the cinematic Dilophosaurus were both fictitious features incorporated for dramatic effect. However, since these embellishments were based on the genetics of other live species, they were realistic. When Welles mentioned the Dilophosaurus fossils, he identified some of the joints between the tooth-bearing bones at the end of the snout as “hard,” implying that the creatures were scavengers or that they killed with claws on their hands and feet. Crichton created a dramatic device for the animals to spew blinding venom while writing the novel, based on certain modern species of cobras that can spit two metres.
The modern frilled agamid lizard, which lives in Australia and New Guinea, provided inspiration for the frill. The frill is supported by a bone and cartilage system that originates from the lizard’s throat. There is no proof of such a trait in Dilophosaurus’ fossil record.
Other elements of Jurassic Park were based on cutting-edge research. Paleontologists were beginning to agree in the early 1980s that modern birds are derived from dinosaurs and are the last living dinosaur lineage. Early prototype illustrations of sinuous, snakelike velociraptors were discarded in favor of suggestions from their scientific mentor, dinosaur paleontologist Jack Horner, to make the animals’ motions more birdlike. The movie was the first time many members of the general public experienced the bird-dinosaur association, with its portrayal of dinosaurs as simple, smart animals rather than the slow, more lizardlike beings that 19th-century scholars believed they were.
NEW AND IMPROVED
Aside from artistic decisions, scientific understanding of Dilophosaurus was bound to evolve in the years following the publication of Jurassic Park. The world of palaeontology was experiencing considerable change in the years leading up to the publication of the book and film. Computing advances were revolutionizing the study of fossils, allowing researchers to process massive data sets in ways that were impossible when Dilophosaurus was first discovered.
Take cladistic analysis, for example, which describes distinct, heritable anatomical characteristics that can be contrasted between animals and provides a statistical framework for evaluating theories about animal relationships. Researchers can now study a greater number of features in a shorter amount of time than ever before, allowing them to establish more well-supported theories on how dinosaurs are related and evolved. Increased computer resources and advancements in medical and industrial CT scanning have also resulted in a nondestructive way to examine secret anatomy between bones and rocks.
Not only did palaeontologists’ analytical instruments improve, but in 1998, teams from the University of Texas at Austin started recovering more Dilophosaurus remains in the same northern Arizona area where the first discoveries were made. A recent fossil discovery has the potential to confirm or disprove previous theories regarding long-extinct species. Sections of the Dilophosaurus anatomy absent or distorted in previously collected samples are retained in the new fossils.
To preserve fossils on their travel from the field to the museum, they are usually collected in big blocks of rock and coated in plaster. Paleontologists use dental picks, chisels, and small portable jackhammers to gently scrape the stone and reveal the fossils until they arrive at the museum.
The fossils we discover are usually warped and missing components after millions of years of exposure to geologic phenomena such as crushing and weathering. Disassembling and reconstructing fragmented pieces to help approximate their initial state, sculpting and inserting missing content based on closely related species, is something we sometimes do. Wann Langston, Jr. and his colleagues at U.C. Berkeley filled in missing skull pieces with fossils from a more accurate carnivorous dinosaur from the Jurassic. They shaped missing parts of the pelvis out of cement as they designed the first Dilophosaurus fossils around 1950. No one knows what those missing pieces looked like, so the analyses served as a prediction for Dilophosaurus’ actual type, which could be checked with new fossils.
Since Welles’ initial classification and Langston’s reconstruction, further Dilophosaurus evidence has been found, revealing that the animal’s snout and jaw were much more significant than previously thought. The poor design that the fragmentary first finds indicated may not exist in the upper jawbones. These bones, on the other hand, point to a robust skull capable of biting into prey.
Similarly, recently discovered characteristics of the animal’s lower jawbones reveal stout ridges for muscle attachments. These ridges offer surface space for the connection of massive muscles in modern reptiles.
Bite marks have since been discovered on the bones of a different dinosaur found at the U.T. Austin dig site, the plant-eating Sarahsaurus, indicating the existence of a massive meat-eating beast with jaws hard enough to puncture bone. Much of this information points to Dilophosaurus being a predator with a lethal bite rather than a beast that had to scavenge or attack with its teeth, as Welles suggested. Dilophosaurus was a massive dinosaur, even by dinosaur standards.
Most dinosaurs from the Late Triassic period of western North America were the size of turkeys or eagles only 20 million years ago. Still, Dilophosaurus may have towered above a person, reaching up to eight feet tall and reaching up to 25 feet long when fully developed.
Its limbs were significantly more prolonged and heavier than those of more giant meat-eating dinosaurs like Allosaurus and Ceratosaurus, and its legs were also considerably longer. When the first Dilophosaurus fossils were discovered, scientists assumed the genus was similar to the carnosaurs Allosaurus and Streptospondylus, so they rebuilt the pelvis to appear as it did in those dinosaurs.
Later, better-preserved Dilophosaurus skeletons reveal a pelvis morphology that is transitional between Coelophysis-like and Allosaurus-like species from the Triassic Period and Late Jurassic, respectively. Dilophosaurus, like many other early dinosaurs and all modern birds, had fleshy air pockets expanding into its vertebrae, which added strength while also lightening the skeleton.
These air sacs provided for the unidirectional air passage into the lungs, which allows birds and crocodilians to complete the cycle in a single breath. This respiration method delivers more oxygen to the animal than mammals’ reversible respiratory systems, which enable air to circulate in and out of the lungs. Dilophosaurus was most likely a swift, agile hunter since animals that breathe unidirectionally have increased metabolism and high activity levels.
According to CT imaging, these air sacs were also found in the bones around the dinosaur’s brain and connected to the sinus cavities in the front of the skull. A ridge of bone forms a canopy over a gap in the skull in the front of the eye sockets known as the antorbital fenestra of most meat-eating dinosaurs. However, in Dilophosaurus, this opening runs parallel to the side of the dinosaur’s distinctive crests, implying that the crests had air sacs as well.
The crests were almost definitely coated in keratin, the same substance that gives horns, claws, and hair their shape, and they may have helped members of this genus recognize one another or attract mates. However, it’s unknown how the air sacs assisted these or other crest features.
Understanding physical change within and within taxonomic classes is one of the difficulties of researching any species’ evolutionary history.
Welles believed that the different skeletons that we now classify as Dilophosaurus represented several genera. One of us (Marsh) used the most up-to-date cladistics methods to test the theory by finding hundreds of anatomical features on each human skeleton and comparing them to one another. The findings of this statistical study reveal that, according to Welles’ hypothesis, all of the animals are so alike that they must all belong to the same genus and species.
Marsh has used these anatomical traits to equate Dilophosaurus to other fossils worldwide in a much more comprehensive data collection. This method clarifies the early developmental history and biogeographical spread of dinosaur species, allowing Dilophosaurus to be placed more accurately on the tree of life. We now know that there is a significant evolutionary distance between Dilophosaurus and its nearest recognized kin, meaning that even further, closer descendants have yet to be found.
Our understanding of the universe in which Dilophosaurus existed has progressed in lockstep with our knowledge of the species. The trek down the Adeii Eichii Cliffs to the Dilophosaurus quarry is a trip back in time to the Early Jurassic, 183 million years ago.
Dinosaurs roamed the area back then, leaving tracks across the Colorado Plateau in what is now sandstone. We drive on overgrown rutted two-tracks that pass the open sandy dune fields that appear on our geologic maps as “QAL”—Quaternary alluvium. Paved surfaces stop miles from the rock outcrop, so we drive on overcrowded rutted two-tracks that pass the open sandy dune fields that turn up on our geologic maps as “QAL”—Quaternary alluvium. Our field vehicles were trapped in 2014 due to windblown sand.
The Navajo Sandstone, the lithified remnants of a 180-million-year-old desert, forms the bedrock under these modern dunes. Ward Terrace’s red rock badlands stretch out to the western coast, where they cross the much younger volcanic San Francisco Peaks of Flagstaff, Arizona. The Grand Canyon, one of the world’s most explored geologic features, is located to the northwest. These habitats retain much of the last 1.8 billion years of the rock record, from the sands that stuck our pickup atop Ward Terrace to the Vishnu schist—the black rock at the bottom of the canyon that is being carved away by the Colorado River.
We work as paleontologists to decipher the life enshrined in those rocks, and we use geologic and biological evidence preserved within them to recreate deep-time environments.
One of our goals was to more accurately establish the age of the Kayenta Formation, the rock in which Dilophosaurus is located. Rivers, wetlands, and streams east of a volcanic arc depositing ash and fine-grained debris into the city laid down this soil. The ash helped to conserve Dilophosaurus’ bones as well as early attempts to date the Kayenta Formation.
We used radiometric techniques to gather fresh rock samples to date. We ground and extracted zircon crystals from the models, which can retain unstable uranium isotopes. The uranium isotope decays into lead at a steady rate.
We calculate the relative amounts of uranium and information as we vaporize the crystals with a laser and test them with a mass spectrometer suggest when the rock layers were laid down. It was about 183 million years ago, plus or minus a few million years, when this Dilophosaurus site was discovered.
Thus, Dilophosaurus lived during the Early Jurassic period, about five million to fifteen million years after the end-Triassic mass extinction, which resulted in the extinction of roughly three-quarters of all life on Earth, including much of the giant reptiles that battled for food with Dilophosaurus. The early dissolution of the supercontinent Pangaea when the northern Atlantic Ocean finally opened like a volcanic zipper is thought to have caused the mass extinction.
The North American tectonic plate moved northward from a subtropical climate belt into an arid climate belt during the Triassic Period and Early Jurassic. As a result, Dilophosaurus’ habitat shifted from roughly the latitude of modern-day Costa Rica to modern-day northern Mexico. As a result, the Kayenta Formation was formed in a seasonally dry climate, with sand dunes migrating in and out of wetter areas where animals thrived. Other species’ fossils discovered in the Kayenta Formation show how Dilophosaurus fit into the environment.
The apex predator in the river oasis called home a conifer-lined waterway that snaked across a sand sea. Two individuals of the long-necked herbivore Sarahsaurus were discovered in the same quarry as one specimen located at U.T. Austin. These dinosaurs coexisted with Megapnosaurus, a smaller meat-eating dinosaur, and Scutellosaurus, a small armored dinosaur.
The early turtle Kayentachelys, which swam alongside heavily scaled bony fish, freshwater coelacanths, and lungfish, is the most common species found in the Kayenta Creation. Dilophosaurus preyed on early mammal ancestors such as the beaverlike tritylodontids and the ratlike morganucodontids.
With some soft brushing, a complete Velociraptor skeleton emerges from the Jurassic Park fossil excavation. Dinosaur fossils are primarily present as fragmented, scarcely distinguishable fragments in the natural world.
On a good day, you could find a mostly entire bone. Dilophosaurus has been the best-documented Early Jurassic dinosaur in the world since Marsh’s detailed anatomical analysis was published last summer. However, it took decades to uncover new fossils filled with the gaps in the animal’s anatomy. And it took many years of paleontologists to figure out what the bones meant. Museums are crucial in fostering those efforts.
FOSSILS FOR ALL
The public’s perception of museums is of a brightly lit display hall, but a natural history museum’s primary purpose is to research the natural world. In the end, these agencies amass vast stocks of specimens that can be used as proof of experimental studies. The models are carefully documented and preserved by teams of professionally qualified conservators, archivists, and collection managers to permanently make the collections available to researchers.
Other scientists must be able to corroborate our results, which is a cornerstone concept of scientific science. In paleontology, this ensures that the fossils must be stored in a museum so that future generations of scientists can examine them and double-check their findings.
The Navajo Nation has worked with museums that care about such fossils to conserve the bones and the collections and data that go with them. We were fortunate to encounter John Willie, a relative of Jesse Williams, the Navajo man who discovered the first Dilophosaurus bones in 1940, while we went to relocate the initial Dilophosaurus discovery site for this study in 2015.
Willie led us to the location and clarified that the Diné value the natural resources specific to the Navajo Nation (Navajo People). The Navajo Nation is one of the best areas in the world to see Early Mesozoic terrestrial rocks, and its Minerals Department has been instrumental in promoting science exploration by granting fieldwork licenses, loaning fossils, and reading scientific manuscripts.
The Navajo Nation is one of the best areas in the world to see Early Mesozoic terrestrial rocks, and its Minerals Department has been instrumental in promoting science exploration by granting fieldwork licenses,
loaning fossils and reading scientific manuscripts. Building from and reevaluating previous experience and even overturning outdated notions is how scientists gain scientific insight.
It’s fun as this hard-won knowledge makes its way into popular culture. Paleontology has a long history with film, dating back to the early days of animation. The animator and a group of friends visit the American Museum of Natural History in Winsor McCay’s 1914 Gertie the Dinosaur. McCay stakes his party on his ability to bring the dinosaur to life, and the result is the first dinosaur video. On his restoration of Gertie, McCay sought advice from paleontologists at the museum. Later, Barnum Brown, the discoverer of the Tyrannosaurus rex, assisted Walt Disney in the making of Fantasia, a 1940 animated film.
The studio behind the 1954 Godzilla found inspiration for its monster’s creation in the dinosaurs depicted in Rudolph Zallinger’s 1947 mural The Age of Reptiles, which is now located at the Yale Peabody Museum. We’re excited to see how paleontology is portrayed in the Jurassic Park film series, which is scheduled to release its sixth installment in 2022. In reality, the opposite is also absolute. Pop culture, in some cases actually, seeps into science.
The paleontologists at U.C. Berkeley in the 1930s and 1940s would dissolve cellulose acetate film strips in acetone to make glue instead of buying the more costly Duco Cement, according to Langston. So, yeah, Dilophosaurus appears in films. However, it’s possible that Dilophosaurus contains a smidgeon of the movies.