Creationism’s problems with the fossil record now extend even to dinosaur droppings. A small piece of fossilised dung from Montana preserves evidence of a meal eaten some 66 million years ago — long before the supposed ‘Creation Week’ of young-Earth creationism. Within it are feathers that may help illuminate why some ancient birds disappeared while the ancestors of today’s birds survived. As, reported in Current Biology, researchers led by Field Museum palaeontologist Jingmai O’Connor, examining a coprolite — fossilised faeces — from the Hell Creek Formation found exceptionally preserved feathers alongside fish scales and bones belonging to a hesperornithiform, an extinct diving bird.
The feathers combine structures associated with waterproofing in modern aquatic birds with smaller, simpler, fuzzy body feathers. The researchers suggest that differences in insulation, feather replacement through moulting, or both might have influenced which bird lineages survived the cold conditions following the end-Cretaceous asteroid impact. Hesperornithiforms disappeared; the lineage containing all living birds survived. This remains a hypothesis, however: one coprolite cannot establish why entire groups became extinct. The distinction between the observed feathers and the proposed explanation is central to the Field Museum’s account of the findings.
For creationists, the difficulty goes beyond the date. This combination of ancestral and more derived features makes sense within an evolutionary family tree, in which different characteristics change at different rates. Evolution does not require every part of an animal to move together along some imaginary ladder from ‘primitive’ to ‘advanced’. Nor does an extinct bird need to be a direct ancestor of living species to preserve evidence of the evolutionary history they share. There is also a useful lesson here about adaptation. A feature that works adequately in one environment may become a liability when conditions change. Evolution has no foresight: natural selection cannot prepare organisms for an asteroid impact millions of years in the future. Survival depends on the circumstances organisms encounter and the characteristics they already possess, with chance also playing its part. What makes this discovery particularly telling is how an apparently unpromising object can yield evidence against which explanations can be tested. Scientists can investigate both the history of feathers and the unresolved details of extinction without invoking a designer. The uncertainty concerns which natural factors mattered most — and further fossils may help resolve it. Even a dinosaur’s discarded meal can contribute to that process.
Hell Creek^ How Do We Date a Lost World? The Hell Creek Formation is one of North America’s most important windows into the closing stages of the age of non-avian dinosaurs. Exposed across parts of Montana, North Dakota, South Dakota and Wyoming, it preserves a succession of ancient environments leading up to the end-Cretaceous mass extinction, approximately 66 million years ago.The paper in Current Biology is accompanied by Field Museum press release:
What is a geological formation?
A formation is a body of rock distinguished by recognisable physical characteristics that geologists can map across an area. It need not represent one environment or one moment in time. Hell Creek contains numerous layers of sandstone, siltstone and mudstone deposited as rivers shifted course and sediment accumulated across floodplains.
Consequently, two fossils described as coming from “Hell Creek” need not be precisely the same age. Their positions within the succession matter. The formation records an extended history, rather than a single burial event.
A landscape with a living ecosystem
The landscape preserved in these rocks differed considerably from today’s exposed badlands. Rivers crossed vegetated lowlands, with floodplains, ponds and wet areas providing habitats for diverse organisms. Alongside famous dinosaurs such as Tyrannosaurus rex and Triceratops, the fossil record includes plants, fish, turtles, crocodilian relatives, amphibians, mammals and birds.
The feather-bearing coprolite belongs within this ecological setting. As the Field Museum explains, its contents include fish scales, diving-bird bones and feathers. Such remains preserve evidence of feeding relationships as well as the animals themselves.
How do scientists establish its age?
Geologists combine several kinds of evidence. Stratigraphy establishes the order of layers: in an undisturbed sedimentary sequence, lower beds generally formed before those above them. Tracing and correlating layers between exposures allows researchers to connect separate fossil sites.
Numerical ages require additional evidence. Volcanic ash deposited among sedimentary layers can contain minerals suitable for radiometric dating. These minerals act as natural clocks because radioactive isotopes change into other isotopes at measurable rates. Crucially, the clock belongs to the volcanic mineral, not automatically to every grain in the surrounding sandstone.
One important method is argon–argon dating, based on the radioactive decay of potassium-40 to argon-40. Laboratory measurements of argon isotopes allow researchers to calculate when suitable volcanic minerals cooled and began retaining argon. Where ash was deposited soon after eruption, this provides an age for that level in the sedimentary succession.
For example, researchers used volcanic ash from the Hell Creek area to refine the timing of the extinction boundary, comparing their results with ages obtained from material formed by the Chicxulub impact. The University of California, Berkeley’s account of this research explains how the measurements brought the impact and extinction dates into close agreement around 66 million years ago.
Carbon dating is not the method used here. Carbon-14 is useful over tens of thousands of years, not the tens of millions separating us from the Cretaceous.
Does every fossil have an exact date?
No. A fossil’s age is usually constrained by its geological position and its relationship to dated layers. Suitable ash beds above and below a fossil-bearing horizon can bracket its age, while correlations with other sections provide further constraints. Researchers must also consider whether erosion moved an older fossil into younger sediment.
The precision therefore varies between specimens and localities. Saying that this coprolite is approximately 66 million years old does not mean that its feathers were directly radiometrically dated, or that every Hell Creek fossil dates from the moment of the asteroid impact.
For young-Earth creationism, the difficulty is that these ages arise from physical measurements combined with a testable sequence of geological events. They are not numbers assigned simply because scientists “believe in evolution”. Disputing them requires explaining the measurements and the rocks, not merely rejecting the timescale they reveal.
Glossary
- Formation
- A mappable body of rock identified by its physical characteristics.
- Stratigraphy
- The study of rock layers, their sequence and their relationships.
- Horizon
- A particular level within a sequence of rock layers.
- Radiometric dating
- Calculating an age using radioactive decay and measurements of the relevant isotopes.
- Isotope
- A form of an element with a particular number of neutrons in its atomic nucleus.
- Coprolite
- Fossilised faeces, which may preserve evidence of an animal’s diet.
- K–Pg boundary
- The boundary between the Cretaceous and Palaeogene periods, associated with the mass extinction approximately 66 million years ago.
A fossil feather preserved inside dinosaur poop could help explain why birds survived the mass extinction
About 66 million years ago, a dinosaur—maybe a T. rex or a Nanotyrannus—ate a bird. The record of that meal, in the form of fossilized poop, has survived to today, preserving the best example of a feather ever found from the age of dinosaurs. And by studying this feather, scientists reported in a new study in the journal Current Biology, researchers have found clues that help explain why birds are the only group of dinosaurs that survived the mass extinction 66 million years ago.
It’s such a beautiful, well-preserved feather, from such an unexpected source, and it’s exciting that it could help us answer this huge question in paleontology.
Jingmai O’Connor, lead author.
Negaunee Integrative Research Center
Field Museum of Natural History
Chicago, IL, USA.
Birds are a specialized kind of dinosaur, and they've been around for a long time. The earliest known bird is Archaeopteryx, from 150 million years ago, and birds continued to evolve and co-exist alongside their fellow dinosaurs for nearly 100 million years. In the aftermath of the Earth’s collision with an asteroid 66 million years ago, nearly all the dinosaurs, including nearly all the birds, went extinct. But one group of birds, Neornithes, survived, and every living bird today is one of their descendants.
One of the biggest mysteries in paleontology is why this one small group of birds survived, when all the other birds and all the other dinosaurs died out. O’Connor has spent years studying fossil birds to try to answer this question. But this is the first time she’s studied feathers that were preserved inside fossilized droppings, or coprolites.
As far as I know, no one has ever thought to look for feathers or to study feathers in coprolites, so this project was really exciting.
Jingmai O’Connor.
The fossil itself came to light in 2016, when David DeMar, Jr., a research scientist and the Hell Creek Project collections manager at the University of Washington Burke Museum and co-author of the paper, was conducting fieldwork in northeastern Montana.
I was crawling up a rocky outcrop collecting fish fossils when I came across a dark, reddish-brown nodule about half the size of a golf ball. I picked it up and scanned its surface through my hand lens, and that's when I couldn't believe what I was seeing, a tiny fossil feather. I was cautiously optimistic about its discovery, because feathers had not yet been found in the Hell Creek Formation, even after more than 150 years of prospecting.
David J. DeMar, Jr., co-author
Department of Paleontology
Burke Museum of Natural History and Culture
University of Washington
Seattle, WA, USA.
Back in the lab, the researchers examined the specimen’s mineral composition and took CT scans of it—essentially, thousands of X-rays that are digitally stacked to reveal the contents of an object.
Although the preservation was better than many of the feathers I’d been studying in Burmese amber for my thesis, this was in a rock—and a fairly unremarkable one at that. I suspected it might be a coprolite, but it wasn’t until we got it into the micro-CT scanner at USC’s medical campus that the full feathery fabric of this fossil feces became apparent. Every hour processing the data revealed another feather, another scale, another bone—in stunning 3D. As someone who had been relying on far-flung amber mines as my main source of 3D feather data, realizing that fossil poop from my home state could yield such exceptional specimens was a game changer.
Nathan R. Carroll, co-author.
Carter County Museum,
Ekalaka, MT, USA.
The coprolite contained multiple feathers, tiny fish scales from a gar, and leg bones from a hesperonithiform bird. Since the bones and feathers, it stands to reason that the feathers came from that bird.Hesperornithiforms were aquatic birds, ecologically similar to loons. Most couldn’t fly, and instead, they used their specialized feet to dive down into the water to hunt for things like fish. The feathers showed adaptations for being underwater that we see in living aquatic birds.
Jingmai O’Connor.
The hesperornithiforms are close cousins of the Neornithes birds that survived the mass extinction and still live today, but they were not part of Neornithes themselves.
The most common birds alive in the Cretaceous were part of a group called the enantiornithines. The modern Neornithes branch of birds were separate from that group, and so were the hesperornithiforms.
Jingmai O’Connor.
Some scientists have hypothesized that the Neornithes branch of the bird family survived because they lived near water, and something about this habitat helped buffer them from the effects of the mass extinction. However, the hesperornithiforms also lived by water, and they went extinct. So, there must be another reason to explain why Neornithes are the only birds that survived. O’Connor thinks one of the main reasons has to do with differences in their feathers.
We think the types of feathers that these birds had, and/or the way they molted those feathers, may have been one of the underlying causes of the selectivity of the end-Cretaceous mass extinction—essentially, why some birds died out and why others survived. Some of these diving birds’ feathers seem to have been modern-looking and water-proof, but they also had some smaller, fuzzy, primitive body feathers that we associate with dinosaurs and enantiornithines.
Jingmai O’Connor.
The feathers found in the coprolite are the first hesperornithiform feathers ever found, and their features seem to represent a middle ground between the feathers of enantiornithines and modern birds. The feathers on a bird’s body help insulate it from the cold. If the hesperornithiforms’ and enantiornithines’ feathers weren’t as good at keeping their bodies warm as Neornithes’ feathers, that could have been a major factor in these groups’ abilities to survive the impact winter following the asteroid strike 66 million years ago.
And since hesperornithiforms are neither neornithines or enantiornithines, the discovery of the feathers in the coprolite also help explain why these diving birds died out.
The hesperornithiforms retain primitive feather types that may not have been as efficient for insulation as modern plumaceous feathers, and that could explain why they went extinct along with the enantiornithines.
Jingmai O’Connor.
[… the study’s findings are important because] we rarely find fossils of birds and even more rarely their feathers, giving us such important insight into the evolution of this key aspect of their biology. On top of that, these bird feathers found within a large fossilized dinosaur dung give us an incredible window into predator-prey interactions 66 million years ago.
Professor Gregory P. Wilson Mantilla, co-author.
Department of Paleontology
Burke Museum of Natural History and Culture
University of Washington
Seattle, WA, USA.
For O’Connor, the study also highlighted the way that paleontology is like solving a mystery. “I usually work with fossils that are preserved in big stone slabs, and the entire skeleton and even the soft tissue is preserved—they make it easy for me. But with this project, we just had this coprolite—and its contents—to go off of, and it made me feel like a detective, piecing together all these little clues,” says O’Connor.
And since no one has studied feathers in coprolites before, this opens up a whole new avenue for investigation. We only knew to look at this one because of how it happened to be split open, with the feather exposed—it was literally a lucky break. I hope more scientists start CT scanning coprolites and taking a closer look at them to see what might be inside.
Jingmai O’Connor.
This study was contributed to by Jingmai O’Connor (Field Museum), David DeMar Jr. (Burke Museum of Natural History and Culture/University of Washington), Nathan Carroll (Carter County Museum), Karen Chin (University of Colorado, Boulder), Michael Holland (Burke Museum of Natural History and Culture/University of Washington), Alex Clark (Field Museum and University of Chicago), Christian Cooper (Field Museum), Pei-Chen Kuo (Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences), Thomas Tobin (University of Alabama), Aaron Celestian (Natural History Museum of Los Angeles County), David Bottjer (University of Southern California), Luis Chiappe (Natural History Museum of Los Angeles County), and Gregory Wilson Mantilla (Burke Museum of Natural History and Culture, University of Washington).
Publication:
Creationism’s difficulty with this discovery begins with its age, but does not end there. Some 66 million years ago, a predator consumed a bird whose remains would eventually provide evidence of an ancient ecosystem and the evolutionary history of feathers. Compressing that history into a few thousand years requires dismissing the geological evidence, while insisting on separately created “kinds” offers no scientific explanation for the mixture of ancestral and more derived features preserved in the plumage.
The possible connection between feather structure and extinction illustrates another fundamental feature of evolution: adaptation comes without foresight. Plumage adequate for life in a Cretaceous ecosystem might have proved inadequate during the environmental upheaval following an asteroid impact. If differences in insulation or moulting helped determine which birds survived, their consequences depended on circumstances that natural selection could never anticipate. There was no evolutionary plan to produce the birds we see today.
That explanation remains a hypothesis, however. One coprolite cannot demonstrate why entire bird lineages disappeared, and distinguishing the effects of insulation, moulting, food availability and other factors will require more evidence. This is how science proceeds: an observation suggests an explanation, which must then withstand further investigation. Acknowledging uncertainty about the details is part of that process.
Meanwhile, the fossil itself remains an extraordinary record of ordinary biological events: feeding, digestion and the disposal of waste. From those unremarkable beginnings comes another opportunity to investigate a world vastly older than the biblical chronology allows. Even fossilised dinosaur dung, it seems, has more to tell us about the history of life than a creation story written by people who knew nothing of that history.
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