Kenneth Lacovara on Dinosaur Evidence—and What Fossils Cannot Tell Us

Joe Rogan says he invited paleontologist Kenneth Lacovara after encountering people who deny dinosaurs existed, including arguments based on museum replicas. Lacovara says initial skepticism is appropriate for a large claim, but a worldwide fabrication would require a conspiracy spanning countries, generations and researchers who never met.

The guest says skepticism helped early researchers scrutinize the first claims about dinosaurs. But an alternative explanation would have to account for consistent finds by independent people on different continents and at different times.

Lacovara has excavated dinosaurs himself, but asks listeners to consider testable predictions rather than rely on his word. The age and type of local rock help predict which fossils might be found: upstate New York has rocks too old for dinosaurs, while much of Florida has rocks that are too young.

For non-avian dinosaurs, he says to look for exposed sedimentary rock roughly 237 million to 66 million years old. He makes the qualification because birds are dinosaurs. He is unsure whether denial has actually increased, suggesting that more people now have platforms to express it.

Lacovara gives an Earth-age estimate of about 4.567 billion years and says he does not personally know whether dinosaur denial has recently become more common. Rogan says he has encountered it more often online in recent years.

To picture deep time, the speakers compress Earth’s roughly 4.5-billion-year history into one calendar year. Lacovara places early dinosaurs in December, their disappearance in the impact at the end of the month, and Homo sapiens about 20 seconds before midnight on New Year’s Eve.

On the same calendar, Lacovara places the rise of abundant complex life around late November and emphasizes how much time preceded dinosaurs. Rogan is struck by how recently humans appear on that scale.

Most organisms never become fossils. A deer or raccoon dying in a backyard will usually decay, be scavenged or weather away; the odds for an individual are extremely low. Lacovara says rare preservation can still yield many fossils when enormous numbers of organisms live over immense periods.

The fossil record is also selective. Lowlands, floodplains and coastlines accumulate sediment and can bury remains, whereas mountain environments tend to lose sediment through erosion. Lacovara expects many dinosaurs and whole habitats will remain unknown because their inhabitants had little chance of being preserved.

Asked about the La Brea tar pits, he calls the remains subfossils because the original bone material is not extensively mineralized. During permineralization, dissolved minerals precipitate in pores in bone; the result can become a mineral-rich copy, although original bone or even soft tissues can sometimes survive.

Rogan asks about a reported dinosaur-blood discovery. Lacovara says the specific report is debated and cites concerns raised by Mary Schweitzer about the structures and sampling. He considers preservation possible but says the claim needs further validation.

There is no known non-avian dinosaur DNA, Lacovara says, and the oldest DNA recovered is far younger than the extinction. He discusses speculative alternatives such as studying dormant traits in birds or genes in relatives, rather than suggesting that Jurassic Park-style recovery is currently possible.

Rogan wonders whether a large living bird might be a better starting point for experimentation than a chicken. Lacovara says chicken genetics has been studied extensively because chickens are commercially important; neither claims the experiment has recreated an extinct species.

A social-media example of an object rapidly mineralized leads to a distinction between fossilization and age. Lacovara says early stabilization must often happen quickly enough to prevent decay; depending on chemistry, some mineralization might begin over months or years, while more extensive mineral replacement can take far longer.

In a mudslide hypothetical, Lacovara says mineralization could begin within months under favorable conditions, producing something he would initially call a subfossil. He distinguishes that from complete mineral replacement, which may take thousands of years or longer and is not inevitable.

The rarity of preservation does not mean fossils must be scarce overall: many generations over vast stretches of time provide many opportunities. Rogan asks how early observers explained strange bones before the scientific category of dinosaurs existed.

Lacovara describes Adrienne Mayor’s work on folk paleontology, which considers whether fossils contributed to legendary creatures. He presents proposed links between Protoceratops fossils and griffins, or dwarf elephant skulls and cyclopes, as possible interpretations rather than established origins.

Early nineteenth-century British dinosaur discoveries were fragmentary. Lacovara says Richard Owen grouped Megalosaurus, Hylaeosaurus and Iguanodon as dinosaurs in 1842; he initially misspeaks and corrects himself from Megalodon to Megalosaurus after the interruption.

Benjamin Waterhouse Hawkins’s Crystal Palace sculptures show how early artists reconstructed animals from limited remains. The models reflected what was then known and looked very different from modern reconstructions.

A nearly complete Hadrosaurus skeleton was found in southern New Jersey in 1858 and became an early mounted dinosaur display. Lacovara describes the public excitement it generated and calls Britain the birthplace of dinosaur paleontology and southern New Jersey one of its early centers.

The first mount attracted crowds, Lacovara says, helping establish lasting public enthusiasm for dinosaurs. He also notes that an early tyrannosaur was found near his current museum in New Jersey.

Rogan asks how the first mount’s posture was determined. Lacovara says its upright, tail-supported pose is now considered wrong: current reconstructions generally place the spine closer to horizontal. New evidence can change the interpretation of an old specimen.

A fleshed-out reconstruction is more than an arbitrary guess but includes uncertainty. Researchers compare living animals and relatives, while acknowledging that color, fat and soft-tissue structures may be unknown. Rogan notes that a hippo’s skeleton alone would not reveal its familiar exterior.

They compare dinosaur reconstructions with the skeletons of hippos, elephants and birds. Lacovara says an elephant’s trunk, for example, might be hard to infer from a skeleton alone; unknown soft tissue places limits on a reconstruction.

Hadrosaurs are relatively well represented because they lived in environments favorable to sediment accumulation. Lacovara says some specimens preserve skin and gut contents, including material useful for identifying plants they ate; he points to the three-dimensional specimen nicknamed Leonardo.

Lacovara explains that some hadrosaur specimens preserve three-dimensional body outlines, skin and material from the digestive tract. He is careful to distinguish preserved gut contents from preservation of the gut itself.

Looking at fossil-bearing rock, Lacovara tentatively identifies what might be floodplain deposits and ancient soils. He marks the interpretation as a guess based on an image rather than a field examination.

Feathers remain a subject of debate across the dinosaur family tree. Lacovara says evidence indicates feathered ancestry among many theropods, though particular descendants may have lost feathers; feather-like structures in other branches raise an open question about the earliest dinosaurs.

Jurassic Park’s Velociraptor is much larger than the animal called Velociraptor, Lacovara says, though other relatives such as Deinonychus were larger. He points to attachment marks on Velociraptor bones as evidence consistent with feathers, while noting that colors in reconstructions are uncertain.

The speakers compare a museum’s feathered and scaly reconstructions. Lacovara says the feathered version is plausible for Velociraptor given the marks on its bones, but colors and elaborate decorative details remain artistic choices.

Lacovara considers why some large modern animals tend to have less conspicuous colors than smaller animals, while Rogan brings up the camouflage of tigers. Their discussion is an analogy, not a direct measurement of dinosaur color.

Lacovara says successive Jurassic Park films retained older-looking models as knowledge changed, particularly concerning feathers. He praises the anatomy of Dreadnoughtus in one film, the giant sauropod he discovered in Patagonia, while explaining that different kinds of size—length, height and mass—are not interchangeable.

He says filmmakers can explain some departures from paleontological knowledge through the fictional premise of genetically engineered animals. He distinguishes those choices from inventions of animals for dramatic effect.

He calls Dreadnoughtus exceptionally massive among dinosaurs for which a body mass can be estimated with confidence, rather than claiming every larger-sounding specimen is smaller. Other giant titanosaurs are known from fragments too incomplete for the same calculation.

For Dreadnoughtus, researchers had both an upper arm bone and a thigh bone. Lacovara says measurements of their shaft circumference can be related to body mass using comparisons with living four-legged animals, producing an estimate of about 65 tons for this specimen.

The structure of its bone suggests the animal was still growing when it died, he says, so the specimen does not establish the species’ maximum size. The speakers compare this with crocodiles, whose growth pattern differs from the determinate growth typical of birds and mammals.

Crocodilians are close living relatives of dinosaurs, not themselves dinosaurs, Lacovara says. Their extinct relatives occupied more varied forms than those alive today, including a North African animal he describes as possibly having a pouch-like feeding structure and others whose locomotion remains debated.

Crocodilians today are only a subset of a historically varied lineage. Lacovara discusses an extinct long-jawed form and says a proposed pouch is inferred from its anatomy rather than recovered soft tissue.

He notes that some ancient crocodilian relatives may have moved on two legs, while acknowledging that the interpretation is controversial. He contrasts their diversity in the Triassic with the smaller early dinosaurs living alongside them.

Asked about stories of extraordinarily large modern crocodiles, he says he does not know of skeletons supporting that size. He does describe very large extinct crocodilians such as Sarcosuchus and Deinosuchus, illustrating that ancient members of the broader group could attain great size.

Rogan asks whether historical stories of enormous crocodiles might be exaggerated. Lacovara distinguishes those accounts from fossil evidence for much larger extinct crocodilians, and avoids claiming that an unverified modern specimen existed.

Why were some prehistoric animals so large? Lacovara says there is no simple answer and notes that giants exist today, including the blue whale. The Mesozoic also contained small dinosaurs; he considers competition between large predators and large plant-eaters a possible part of the story.

The extinct hornless mammal Paraceratherium prompts the same reconstruction question. Its soft tissue is not preserved in the example discussed, so artists look to related animals but cannot know its exact outer appearance from that evidence.

Rogan raises claims that flat-topped rock formations are giant tree stumps. Lacovara instead describes columnar rock forming as molten material cools, and discusses similar-looking structures elsewhere. The exchange separates a geological explanation from the online claim.

Lacovara explains that cooling rock can contract into striking columns, citing familiar examples of columnar formations. The shapes can look artificial or organic but arise through geological processes in his account.

Lacovara links the end-Triassic mass extinction, about 202 million years ago, to volcanism as Pangaea began breaking apart and the Atlantic opened. He says carbon dioxide and rapid warming hit many groups, including crocodilian relatives, while dinosaurs diversified into available ecological roles afterward.

He compares ecological roles left vacant by extinction to job openings. Lacovara says the dinosaur lineage happened to diversify into many of those roles after the end-Triassic event; he does not claim a single proven reason for the different survival of every group.

Dinosaurs then diversified through the Jurassic and Cretaceous, with fossils known from every continent, including Antarctica. Rogan asks why crocodilians survived the later asteroid impact while non-avian dinosaurs did not; Lacovara notes that the fossil record remains incomplete.

Rogan asks whether giant crocodilians might also have survived closer to the end-Cretaceous impact. Lacovara agrees that future discoveries could change the picture; their current answer depends on what the fossil record has yielded.

An asteroid struck near the Yucatán about 66 million years ago, excavating a vast crater and throwing rock through the atmosphere. Lacovara describes a proposed mechanism in which returning debris heated the sky as it reentered. His estimate of the surface conditions is part of that reconstruction.

Lacovara compares reentering fragments to immense numbers of tiny glowing space capsules. He explains the proposed heating as a consequence of the material thrown high into the atmosphere returning and interacting with the air.

He suggests that animals able to shelter underground or in water had an advantage, while many large non-avian dinosaurs and their exposed nests had little protection. He argues that breeding populations of those dinosaurs may have been functionally extinct on the day of impact; he presents this as his interpretation.

He says some living animals can shelter in burrows, while recognizing that one dinosaur finding a cave would not by itself preserve a viable population. Survival depends on enough individuals getting through to reproduce.

Rogan asks about reports of dragons in historical accounts. Lacovara says fossil vertebrae or other remains can invite imaginative explanations; when the speakers inspect an account attributed to Herodotus, they distinguish bones and local reports from a confirmed sighting of a living winged serpent.

The account of Herodotus discussed on screen concerns heaps of bones and a story passed on by locals. The speakers explicitly recognize that an eyewitness report of bones is not the same as verified evidence for living flying snakes.

He returns to folk explanations with fossil shark teeth found in Sicilian fields. People who lacked a geological account of former seas called them serpent tongues. Lacovara describes the attribution as an effort to explain objects in the landscape without modern concepts of deep time.

Repeated finds of shark teeth in fields puzzled people who did not know that marine rocks could be exposed on land. The fossil explanation connects present-day observations to environments that existed long before the fields.

Rogan points to an old church depiction of a whale that looks unlike a modern animal. Lacovara discusses Nicolas Steno’s recognition that supposed serpent tongues resembled shark teeth and his work on how rock layers relate to one another.

Steno compared the shapes of fossils with shark teeth and reasoned that the objects once came from sharks. Lacovara describes simple principles of stratigraphy, including older layers generally lying below younger undisturbed layers.

James Hutton’s interpretation of Siccar Point gives Lacovara an example of reasoning toward deep time. Rock layers were deposited, hardened, tilted and eroded before further layers formed; reconstructing that sequence suggested that the planet had existed for a very long time.

At Siccar Point, the orientation and truncation of older beds beneath younger ones provide clues to a sequence of deposition, hardening, tilting and erosion. Lacovara emphasizes the order of those events as evidence for time rather than treating the outcrop as a clock with a single reading.

Hutton also studied granite and the rock cycle. Lacovara summarizes the principle associated with uniformitarianism as using processes observable today to reason about the past; he contrasts that with assumptions of a much younger Earth common among educated people of the era.

Lacovara describes Hutton as working against prevailing assumptions and says Lyell later communicated related geological ideas to a wider readership. Rogan marvels at how few people then had the background to discuss such explanations.

He traces an intellectual connection through Charles Lyell’s Principles of Geology, which Darwin read during the Beagle voyage. In Lacovara’s telling, geological evidence for deep time gave Darwin room to consider gradual evolutionary change through natural selection.

He says Darwin read Lyell on the voyage and interpreted geological observations through that framework. The resulting sense of a long history, Lacovara argues, helped make slow biological change conceivable.

The speakers reflect on how unusual it was for early geologists to assemble explanations with so little established knowledge to draw on. Lacovara recalls Darwin’s reluctance to publish and the years he devoted to studying barnacles.

The speakers reflect on the difficulty of overturning deeply held ideas. Lacovara says scientists test hypotheses and remain open to falsification, even though researchers are human and can resist challenges to positions they have defended for years.

Lacovara says the ideal scientific response to a falsified hypothesis is to revise it and keep investigating. He also acknowledges that reputations and ego can make that much harder in practice.

As an example of disciplinary change, he recalls professors who held older geological explanations when plate tectonics was becoming established. The anecdote illustrates his view that evidence may spread more slowly than its proponents expect.

He recalls older teachers who resisted plate tectonics and describes how evidence for seafloor spreading helped establish the theory. Magnetic patterns in ocean-floor rock and the formation of new crust at mid-ocean ridges provided a way to understand moving plates, he says.

He describes magnetic bands on the seafloor as records of changing polarity in newly formed rock. Together with mid-ocean ridges, the patterns helped support seafloor spreading as a mechanism relevant to moving continents.

Rogan asks about magnetic reversals. Lacovara says the interval varies greatly, emphasizes that geophysics is not his specialty, and discusses uncertainty about effects during a reversal. The speakers also note that the magnetic pole moves without that movement itself constituting a reversal.

Lacovara notes that the magnetic pole’s position changes over time and says he does not know its current speed. He distinguishes this motion from the separate question of the magnetic field reversing polarity.

Fine magnetic particles can preserve a record of direction in suitable sediments. Lacovara says changes in polarity can help correlate layers across regions, although an interval without reversals gives him fewer matching markers for rocks from the end of the Cretaceous.

Because the polarity sequence has intervals of different lengths, Lacovara compares it to a pattern of stripes that can help align rock records. He says the absence of reversals during one interval he studies makes that correlation tool less useful there.

When pressed for a worst-case guess, Lacovara speculates about radiation and mutation, expressly labeling it a guess. Rogan reads an AI-generated summary saying that evidence does not establish a global catastrophe and that a proposed connection between an ancient magnetic excursion and environmental disruption remains disputed.

The on-screen summary also describes a disputed hypothesis about an ancient temporary magnetic excursion and possible environmental effects. The speakers present it as a proposed scenario, not a demonstrated cause of extinction.

Rogan describes the underground site of Derinkuyu in Turkey and another excavated complex in China, wondering about their construction and use. These are his accounts and questions about archaeology, not evidence that either site was built in response to a magnetic reversal.

Rogan wonders how ancient underground spaces were carved and ventilated and what they were used for. Lacovara responds with a memory of archaeological discoveries near an Egyptian oasis where he worked; the conversation does not establish a shared explanation for the sites.

Rogan brings up accounts of a purported long-necked animal in the Congo. The description he reads says expeditions found no evidence beyond reported sightings. Lacovara says a surviving large animal would need a breeding population, making claims about isolated monsters difficult to reconcile with the absence of evidence.

Rogan reads descriptions of the alleged Congo creature and reflects on how difficult the region can be to explore. Lacovara’s breeding-population question shifts the discussion from a single claimed encounter to the evidence a persistent species would be expected to leave.

They compare stories about lake monsters, large apes and an unsuccessful search for a reported giant sloth. Rogan considers how stories can grow in places where the environment is difficult to inspect, while remaining curious about reports from remote regions.

They discuss how much remains to be found in remote ecosystems. Lacovara says biologists discover species in areas such as the Congo and Amazon, often small organisms, while the speakers distinguish genuine discoveries from unsupported reports of large cryptids.

Rogan describes reports and evidence concerning unusually large chimpanzees, distinguishing actual chimpanzees from claims about an unknown dinosaur-like animal. Lacovara notes that obtaining funding for open-ended discovery can be difficult when researchers cannot promise a find in advance.

Rogan says photographs, samples and observations document chimpanzees in the region, while noting that some colorful local names do not establish the animals routinely kill lions. Their existence is distinct from a claim that a dinosaur-like cryptid survives nearby.

Lacovara says early funding for exploratory research can be hard to secure because funders ask researchers to predict what they will find. Rogan points to the discovery of Homo floresiensis as another case in which evidence changed earlier expectations.

Rogan points to finds of extinct human relatives as examples of discoveries that changed expectations. Lacovara describes human evolution as branching rather than a single straight line and says evidence has challenged old portrayals of Neanderthals as simply brutish.

Lacovara mentions evidence of Neanderthal toolmaking and possible art or burials, and the presence of Neanderthal ancestry in present-day humans. The discussion is about what the evidence can reveal, not a claim that all questions about Neanderthal behavior are resolved.

The conversation turns to genetic reconstruction. Lacovara, who says he advises Colossal, regards recreating a Neanderthal as ethically troubling; Rogan probes the distinction between that hypothetical and projects involving recently extinct animals. Their discussion is about proposals, not proof that extinct species have been restored unchanged.

Rogan and Lacovara debate whether the ethics of bringing back a human relative would differ from conservation projects involving other species. Lacovara expresses reservations about the former; the exchange remains hypothetical.

Lacovara argues that mammoths and other recently lost animals belonged to ecosystems that persist today, and asks where one would draw the line between reversing an extinction immediately and doing so centuries later. Rogan raises the possibility that ecosystems change over time.

Rogan points out that a long-absent species’ former ecosystem may have changed. Lacovara responds that he sees species lost during human history as belonging to the same broad world, while the question of where to draw a line remains a judgment.

Considering how a living human relative might be treated leads to a discussion of animal welfare. Rogan describes distress at seeing primates in small zoo enclosures, while Lacovara recalls observing an elephant manipulating a rock and infers that it was actively exploring its surroundings.

Rogan describes hearing a primate cry in a small enclosure and says the experience made him question such conditions. Lacovara similarly recalls an elephant interacting with a rock; neither observation by itself establishes exactly what the animal was thinking.

Lacovara also credits zoo conservation programs, citing the California condor as an example of captive breeding and reintroduction after a severe population decline. The two distinguish conservation work and larger enclosures from practices they consider harmful to confined animals.

The condor example illustrates what Lacovara sees as a conservation benefit of zoos: an intensive breeding program followed by release. He contrasts this with concerns about the welfare of individual animals in inadequate housing.

Lacovara discusses Prehistoric Planet’s depiction of Dreadnoughtus fighting with its neck. He doubts that a lightly built, long-necked animal would fight that way and says the show’s external inflatable neck structures were speculative, not features supported by the recovered fossils.

The program’s speculative neck bladders are different from anatomical air spaces, Lacovara says. He recalls being warned that viewers might mistake an imaginative visual device for a documented feature of Dreadnoughtus.

He distinguishes those invented external structures from evidence of air-filled spaces in the skeleton. He suggests, without claiming certainty, that connections to a bird-like respiratory system could have helped huge sauropods shed heat; long necks and tails also provided surface area.

Lacovara describes airflow in birds as a more efficient system than the tidal breathing pattern in mammals. His suggestion that a comparable system assisted sauropod cooling is presented as a plausible interpretation, not a direct observation of a living dinosaur.

The speakers discuss living birds as dinosaurs, including birds with unusual traits and chickens that catch small animals. Lacovara points to air-filled bones and other adaptations, and the conversation moves to their own experiences keeping chickens.

They compare the appearance and behavior of modern birds with familiar movie images of dinosaurs. Both men describe keeping chickens and observing them pursue small animals, an everyday example that keeps the evolutionary connection visible to them.

Their conversation about keeping hens includes an unexpected rooster and the practical work of caring for a flock. They also discuss eating eggs from their own birds as a personal preference.

Lacovara describes the Explorers Club and its annual dinner, including its tradition of serving unusual appetizers. He recalls meeting explorers and Apollo astronauts, including a gathering connected to an award he received in 2019.

At an Explorers Club gathering, Lacovara recalls meeting Apollo astronauts and encouraging his son to remember the occasion. The club includes researchers and supporters, and its events also help raise funds.

He says the club supports younger explorers and conservation work and connects members with expertise and logistical help. Rogan returns to the history of dinosaur hoaxes and asks whether scientific competition contributed to distrust of fossils.

Lacovara says fabricated or assembled fossils have existed and have been exposed by paleontologists. He distinguishes those from the nineteenth-century Bone Wars between Edward Drinker Cope and Othniel Charles Marsh: their rivalry was bitter and some identifications were later revised, but the fossils they studied were real.

The Cope–Marsh competition involved access to excavation sites and disputes over interpretations, Lacovara says. Later researchers corrected some identifications and concluded that some names referred to already known species, rather than treating all the early work as fraudulent.

He recounts how a dispute over access to New Jersey fossils fed the rivalry, and how a mistaken plesiosaur reconstruction became a source of public embarrassment. Despite their rivalry, their discoveries left many names that paleontologists still encounter.

Rogan asks again whether the rivalry involved fabricated dinosaur bones. Lacovara says Cope and Marsh worked with genuine fossils, though their haste produced errors and some supposedly new species were later reassigned to existing ones.

A museum skeleton may contain real fossils, casts or a mixture. Lacovara says replicas of large bones protect original material and keep it accessible for research, while a mounted original can be difficult to examine or might require damaging supports. He favors labeling replicas and differentiating reconstructed pieces.

Lacovara says museums should identify which displayed pieces are original and which are replicas. When real and reconstructed bones are mounted together, different colors can help visitors see where evidence ends and reconstruction begins.

Missing anatomy can be inferred by comparing relatives, a method he calls phylogenetic bracketing. For Dreadnoughtus, he says the skull was largely missing and much of the neck had to be reconstructed using related dinosaurs, so those parts carry more uncertainty than better-preserved portions.

To prospect for dinosaurs, Lacovara looks for exposed sedimentary rocks of the right age. Deserts and badlands are useful because the rocks are visible today, not because dinosaurs necessarily preferred deserts. Going where fewer paleontologists have worked can improve the chance of a discovery new to science.

He explains why the ability to access a site matters as much as knowing what may be there. Patagonia’s wind and remoteness make fieldwork difficult, but its exposed rocks have produced significant dinosaur finds.

He names Patagonia, parts of China and the American West as productive regions and would like to explore more of North Africa. With unlimited resources, he would also look beneath Antarctic ice: dinosaur fossils have already been found on exposed parts of the continent, but much remains inaccessible.

He also describes ancient environments unlike the modern setting: North Africa once included coastal habitats, while Antarctic forests experienced long polar darkness. Their present-day exposure and access determine how easily those past environments can be studied.

Lacovara recalls climbing a crumbling rock face with a heavy slab bearing pterosaur tracks on his back. He says he became stranded partway up, then cautiously climbed to the top. The experience changed how he viewed the hazards of fieldwork.

At the Dreadnoughtus site in Patagonia, the team initially crossed a glacial river and used horses to haul plaster-jacketed bones. Lacovara later found a difficult vehicle route; with funding in a subsequent season, a rough road was made, allowing a sustained excavation.

The first transport plan involved placing protected fossils on sleds cushioned with grass and using horses to pull them out. A drivable route made it possible to bring larger equipment and develop the project over multiple seasons.

In Egypt, a local man once mistook him for a grave robber. Lacovara says an Egyptian colleague explained over a radio that he was doing research, defusing the encounter. He contrasts the tense moment with the generosity he experienced during fieldwork.

During the confrontation in Egypt, he chose to contact a colleague rather than let the misunderstanding escalate. Once the colleague explained the work, he says, the interaction became friendly.

He recalls leaving an expensive camera at an Egyptian village stand; several days later, the vendor ran out to return it. Local children also gave him a water buffalo as a birthday gift, which he asked them to care for when he returned to the United States.

He uses the returned camera and the buffalo gift to illustrate the kindness he encountered during expeditions. The stories follow his account of dangerous moments and provide a different view of the same fieldwork.

Lacovara gives Rogan a fossil crocodilian tooth from the extinction layer at the Edelman Fossil Park and shows another crocodilian bone from the research collection. He interprets the layer as recording the catastrophe at the end of the Cretaceous, about 66 million years ago.

The tooth is from an extinct crocodilian Lacovara calls Thoracosaurus. He says fossils and impact-related material at the New Jersey site let researchers investigate a narrow interval at the end of the Cretaceous.

The research layer is managed and curated, while visitors can dig in fossil-bearing material above it and take finds home, Lacovara says. Rogan thanks him and mentions his book, Why Dinosaurs Matter, whose audiobook Lacovara narrates.