New Finds from Tanis Fossil Site Shed Light on the Demise of Dinosaurs and Vindicate “Amateur” Fossil-Hunter

Three years ago the world of paleontology was rocked by the claim of a brash young maverick to have found a site which captured a physical record of events from the very day 66 million years ago that a giant meteorite impacted the earth and (eventually) killed off all the dinosaurs. Robert DePalma had the perseverance and the insight to realize that the initially unpromising location (just some crumbly fish fossils in mudstone) that he took over from another fossil hunter was a unique paleontological site. DePalma and co-workers published a PNAS paper proposing that the Chicxulub meteorite which struck near what is now the Yucatan Peninsula of Mexico caused an earthquake which in turn caused massive waves of water to surge up a creek at the so-called Tanis site in what is now western North Dakota.

The surges deposited several feet of mud onto sandbars in the creek. It also deposited a number of hapless fish onto the sandbars, where the fish eventually perished. The meteorite impact blasted tons of melted rock into the air; little glassy congealed blobs (“tektites”) rained down across western North America for the next several hours. As it happened, some of those glassy pellets were falling in North Dakota just as the mud layers were being deposited on the sandbars from the water surges. Finding these pellets, and even their little impact holes, in the middle of these mud layers confirmed that these layers were in fact deposited a few hours after the meteorite impact. We described these 2019 findings in Tanis Site: The Day the Dinosaur-Killing Asteroid Hit, and discussed how they support the mainstream science view that the earth is billions of years old and that dinosaurs died out millions of years ago.

Rock section showing layers from the Cretaceous Period (when dinosaurs lived), overlaid by boundary layer material from the asteroid strike 66 million years ago, and then younger Paleogene rocks (no dinosaurs). Source: Phil Manning/Uni of Manchester, UK.

An enterprising reporter for the New Yorker had previously interviewed DePalma. Apparently the New Yorker had agreed to wait until after the academic PNAS article published. In a breach of journalistic etiquette, however, the New Yorker published its piece  a few days before the journal article. This set off a flurry of publicity but also led to widespread bad feelings in the scientific community. Skeptical comments by scholars abounded regarding DePalma’s claims.

Robert DePalma with fossil paddlefish at the Tanis site; red arrow points to gill region of the fish, where impact ejecta spherules can be seen (See Tanis Site: The Day the Dinosaur-Killing Asteroid Hit.) From Figure S15-A of Supplement to DePalma et al., PNAS, April 2019.

It seems that some of the dismay in the academic establishment was due to DePalma being considered an amateur, lacking the all-important credential of a PhD degree. Also, he operated at that point as something of a lone wolf, doing or supervising all the work himself, not in conjunction with some prestigious institution. Furthermore, the New Yorker piece contained these tantalizing hints of even more juicy finds, which were not covered in the formal PNAS article:

At the bottom of the deposit, in a mixture of heavy gravel and tektites, DePalma identified the broken teeth and bones, including hatchling remains, of almost every dinosaur group known from Hell Creek, as well as pterosaur remains, which had previously been found only in layers far below the KT boundary. He found, intact, an unhatched egg containing an embryo—a fossil of immense research value. The egg and the other remains suggested that dinosaurs and major reptiles were probably not staggering into extinction on that fateful day. In one fell swoop, DePalma may have solved the three-metre problem and filled in the gap in the fossil record.

The “three-meter” problem refers to the puzzling fact that typically no dinosaur remains are found in the upper 3 meters (10 feet) of rock layers that underlie the world-wide markers of the Yucatan meteorite strike. This has led to speculation that dinosaurs had already died out from other causes, thousands of years before the meteorite impact. The New Yorker article stated that DePalma had found remains showing that dinosaurs were present right up until the impact. This would be huge news, if true, but it remained highly disputed, since the academic PNAS article did not provide clear evidence for these remains.

One frustrated paleontologist  tweeted, “The thing that’s magnificent about this dinopocalypse thing is that there’s something in here that’s almost perfectly hand-crafted for literally each and everyone in or associated with the field to hate about it.”  A writer on Slate savaged the New Yorker article as being “sloppy and sensational”, and complained bitterly that  the “pulp-novel depiction of DePalma as the scrappy young man fighting the stodgy academic system, flexing shirtless beneath the North Dakota sun” supported the “heroic male paleontologist trope”.

Well, here we are three years later, and DePalma has been fully vindicated against his critics. As far as his credentials, in a recent speaker’s bio he made the point that he is far more experienced and capable than your typical newly-minted PhD:  

Robert’s interest in fossils, osteology, and exploration began at a very young age, and formally kicked off when he started working in the Florida Museum of Natural History prep lab at the age of 14. Robert’s fascination with the natural world and artistic media led him to build his skills in drawing, painting, sculpting, fossil preparation, scientific investigation, fleshed reconstructions, museum exhibit design, and visual effects, guided by paleo artist John Gurche, Hollywood visual effects guru Stan Winston, and various professional scientists including Robert Bakker, Larry Martin, Mark Norell, and Walter Alvarez. As a professional scientist, Robert has collaborated with museums and institutions across the globe, including the Florida Museum of Natural History, the University of Kansas Natural History Museum, University of Manchester, American Museum of Natural History, and others. Since 1996 Robert has led over 25 expeditions in the US and abroad in an effort to expand our knowledge of natural history and provide educational opportunity to students from diverse backgrounds. Robert’s research work has included the discovery of the first known dinosaur-aged amber insects from the Hell Creek Formation, discovery and description of the giant dromaeosaurid dinosaur Dakotaraptor steini, documentation of the first known fossil of healed dinosaur skin, and research/excavation of dozens of dinosaur skeletons.

That said, DePalma is pursuing a doctorate at the University of Manchester, UK. More importantly, he has invited a number of outside research teams to the Tanis site (DePalma is leasing the site from the private landowner there) to provide independent examinations of the evidence. Between their results and his own ongoing findings, a trove of new information has been published which sheds fresh light on the mass extinction connected with the meteorite impact.

When Did the Dinosaurs Actually Die Out?

As noted above, the timing of the demise of the dinosaurs has been disputed. It seems clear that none of them survived long after the impact event. (Strictly speaking, modern birds are considered to be in the dinosaur family, but here I use the term “dinosaur” here in the common sense of “nonavian dinosaurs”, i.e. large reptiles, not birds.) The red-hot fallout from the meteorite impact may have roasted many animals above ground, killing them immediately, and the fine aerosol thrown up in the atmosphere apparently darkened the skies around the world, shutting down photosynthesis for long enough to kill off most herbivores and in turn starve the carnivores.

But the fossil record up until now had suggested that dinosaurs may have declined or even died out before the impact. Shortly before the impact event, there was a massive series of volcanic eruptions in the Deccan Traps area of India which released enormous amounts of sulfur dioxide and other gasses in the atmosphere, which probably altered the climate. It has been proposed that this fatally stressed dinosaur populations.

Recent finds from the Tanis site, however, show that there was a thriving population of dinosaurs right up until the asteroid impact. At the October, 2021 meeting of the Geological Society of America, one of DePalma’s students, Riley Wehr, presented a paper titled “ECOLOGICAL STATUS AT THE TIME OF IMPACT: EVIDENCE OF DINOSAURIA AT THE KPG BOUNDARY, HELL CREEK FORMATION, NORTH DAKOTA.”

Fossilized remains of a ceratopsian dinosaur (think: triceratops) were found within the mud deposits formed on the day of the impact:

Source: Riley Wehr et al. paper at 2021 GSA Conference

The soft tissue here was partially decayed, indicating that the animal had died only a few weeks or months before burial in the mud surge, and later fossilization. Also, the footprints of several different types of dinosaurs, both young and old, were present on the sandbar, immediately below the mud deposited on the day of impact:

Source: Riley Wehr et al. paper at 2021 GSA Conference

This testifies to a vibrant community of dinosaurs right up until the impact. The Abstract of this talk sums it up:

…Here, we report new evidence from Tanis, a Chicxulub impact-triggered surge deposit in the Hell Creek Formation, U.S.A., that supports a thriving ecology up to the last minutes of the Cretaceous. The rapidly emplaced sediment package constitutes a “bioclastic time-capsule” that preserves a condensed association of flora and fauna from the first hours after the impact event… Ceratopsian remains, including fossilized osseous and soft-tissue, indicate the presence of Dinosauria until immediately prior to impact. Feathery integument from within the deposit (c.f. Theropoda), and a diverse assemblage of trackways (both theropod and ornithischian dinosaur) in the paleosurface immediately underlying the surge deposit, further suggest an abundant and speciose terminal-Cretaceous biome. Additional fossils from the underlying paleosurface include an abundance of flowering plants and invertebrate burrow morphologies, supporting robust ecological fitness immediately prior to the Chicxulub impact…

Yet More Finds from Tanis: Season of Impact, Fossilized Pterosaur Embryo, and Fragment of the Meteorite

Tanis is the gift that just keeps on giving and giving. Two published articles, one by DePalma and co-workers and another by a Dutch team, examined the fossilized skeletons of the fish that died in the mud deposits. By analyzing growth patterns, they found that it was springtime in the Northern Hemisphere when these fish died and thus when the impact occurred.

DePalma presented a raft of further intriguing finds at a NASA scientific colloquium on April 6, 2022. These included a fossilized egg with the remains of a pterosaur (flying reptile; e.g. pterodactyl) visible inside it:

Fossilized egg with bones of pterosaur embryo in it. Source: Yahoo

Here is a computer modeling reconstruction of this embryo:

Digital reconstruction of  pterosaur embryo in fossil egg in Tanis deposit. Source: Yahoo

Another find was a young  ornithischian plant-eating dinosaur with exquisite lithified preservation of details of skeleton and skin:

Ornithischian dinosaur hip/leg/skin from Tanis site.  Source: BBC

Finally, DePalma reported finding chunks (preserved in amber) of the actual asteroid that smashed into the earth that fateful day. As noted above, little chunks of melted earth rocks from the impact were thrown high and rained down across the globe. However, the asteroid itself was essentially obliterated upon impact, and so we had no conclusive identification as to its composition. But now, thanks to DePalma and Tanis, there is strong evidence that this asteroid was a particular type of carbonaceous chondrite. In the words of the NASA talk abstract:

We also describe two well-preserved meteoric fragments from the same deposit, directly associated with Chicxulub impact ejecta adjacent to the Tanis biota. The fragments are preserved as inclusions within unaltered glassy ejecta spherules, encapsulated immediately after impact while the glass was still malleable. The ejecta spherules, themselves, were preserved in amber coeval with the impact event, which likely increased their preservation potential and inhibited their usual breakdown to smectitic clay. Geochemical examination using energy dispersive X-ray analysis, laser-ablation inductively-coupled-plasma-mass-spectroscopy, and synchrotron X-ray techniques, provided multiple lines of evidence that support a cosmic origin and chemistry indicative of a CM subtype carbonaceous chondrite. Constraining the identity of the Chicxulub impactor using data from this work, which supports prior hypotheses, helps to fill a critical gap hitherto missing from the Chicxulub story.

And Now, Tanis on TV

Robert DePalma has come a long way in three years, from being a scorned outsider to being a rock star in the world of paleontology. A BBC film crew has visited the Tanis site periodically to document the discoveries  there in a manner accessible to the general public. On April 22 the BBC aired a special documentary hosted by Sir David Attenborough called Dinosaurs: The Final Day.  For American audiences, similar material will be presented as a PBS NOVA production as a two-part, two-hour “Dinosaur Apocalypse” special starting at 9 PM ET on Wednesday, May 11. It is quite a story.

APPENDIX: Tanis Data Indicates That Fine Dust from Impact Played Greater Role than Previously Thought

Phys Org has summarized an article by Senel et al in Nature Geoscience, reporting that analysis of samples from the Tanis site indicate that (rock/asteroid) dust was important in shutting down photosynthesis after the impact:

“…exactly how the impact of the asteroid Chicxulub caused all those animals to go extinct has remained a matter of debate.

The leading theory recently has been that sulfur from the asteroid’s impact—or soot from global wildfires it sparked—blocked out the sky and plunged the world into a long, dark winter, killing all but the lucky few.

However research published Monday based on particles found at a key fossil site reasserted an earlier hypothesis: that the impact winter was caused by dust kicked up by the asteroid.

Fine silicate dust from pulverized rock would have stayed in the atmosphere for 15 years, dropping global temperatures by up to 15 degrees Celsius, researchers said in a study in the journal Nature Geoscience.

“…The dust particles were around 0.8 to 8.0  micrometers—just the right size to stick around in the atmosphere for up to 15 years, the researchers said.

Entering this data into climate models similar to those used for current-day Earth, the researchers determined that dust likely played a far greater role in the mass extinction than had previously been thought.

Out of all the material that was shot into the atmosphere by the asteroid, they estimated that it was 75 percent dust, 24 percent sulfur and one percent soot.

The dust particles “totally shut down photosynthesis” in plants for at least a year, causing a “catastrophic collapse” of life, Karatekin said.”