The results of recently analyzed find from the Green River Formation in the western US were published yesterday show the fossilized remains of an entire school of 257 fish. Beyond the fact that a whole school of fish was somehow frozen in time together 50 million years ago, what’s so remarkable is this discovery provides evidence of the social behavior of a now-extinct animal.
We found traces of two rules for social interaction similar to those used by extant fishes: repulsion from close individuals and attraction towards neighbours at a distance. Moreover, the fossilized fish showed group-level structures in the form of oblong shape and high polarization, both of which we successfully reproduced in simulations incorporating the inferred behavioural rules. Although it remains unclear how the fish shoal’s structure was preserved in the fossil, these findings suggest that fishes have been forming shoals by combining sets of simple behavioural rules since at least the Eocene. Our study highlights the possibility of exploring the social communication of extinct animals, which has been thought to leave no fossil record.
Read more about the analysis in Science News.
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It’s only Monday, but I’m confident this will be my favorite read of the week. Since 2012, paleontologist Robert DePalma has been excavating a site in North Dakota that he thinks is “an incredible and unprecedented discovery”. What’s potentially so special about this site? Fossils from dinosaurs and other animals from thousands of years before the asteroid impact are very hard to come by, leading some to believe that dinosaurs died out before the impact, not because of it. DePalma believes the site preserves, as if in amber, the day, the precise and exact day (and perhaps even the exact hour), that the massive asteroid believed to have caused the extinction of the dinosaurs hit the Earth 65 million years ago.
As DePalma carefully excavated the upper layers, he began uncovering an extraordinary array of fossils, exceedingly delicate but marvellously well preserved. “There’s amazing plant material in there, all interlaced and interlocked,” he recalled. “There are logjams of wood, fish pressed against cypress — tree root bundles, tree trunks smeared with amber.” Most fossils end up being squashed flat by the pressure of the overlying stone, but here everything was three-dimensional, including the fish, having been encased in sediment all at once, which acted as a support. “You see skin, you see dorsal fins literally sticking straight up in the sediments, species new to science,” he said. As he dug, the momentousness of what he had come across slowly dawned on him. If the site was what he hoped, he had made the most important paleontological discovery of the new century.
The type of evidence present at the site is almost too good to believe:
He noted that every fish he’d found in the site had died with its mouth open, which may indicate that the fish had been gasping as they suffocated in the sediment-laden water.
“Most died in a vertical position in the sediment, didn’t even tip over on their sides,” he said. “And they weren’t scavenged, because whatever would have dug them up afterward was probably gone.”
Clues from the growth stages of animals and pollen found at the site might even point to what season it was when the asteroid struck…DePalma’s current guess is in autumn. And then there’s this, about a burrow that DePalma discovered:
“Any Cretaceous mammal burrow is incredibly rare,” he said. “But this one is impossible — it’s dug right through the KT boundary.” Perhaps, he said, the mammal survived the impact and the flood, burrowed into the mud to escape the freezing darkness, then died. “It may have been born in the Cretaceous and died in the Paleocene,” he said.
A scientific paper is forthcoming this week. I couldn’t find it online, but this piece in Science says that it’s generating some discussion and controversy already.
“Outcrops like [this] are the reasons many of us are drawn to geology,” says David Kring, a geologist at the Lunar and Planetary Institute in Houston, Texas, who wasn’t a member of the research team. “Those few meters of rock record the wrath of the Chicxulub impact and the devastation it caused.” But not everyone has fully embraced the find, perhaps in part because it was first announced to the world last week in an article in The New Yorker. The paper, in the Proceedings of the National Academy of Sciences (PNAS), does not include all the scientific claims mentioned in The New Yorker story, including that numerous dinosaurs as well as fish were buried at the site.
“I hope this is all legit-I’m just not 100% convinced yet,” says Thomas Tobin, a geologist at the University of Alabama in Tuscaloosa. Tobin says the PNAS paper is densely packed with detail from paleontology, sedimentology, geochemistry, and more. “No one is an expert on all of those subjects,” he says, so it’s going to take a few months for the research community to digest the findings and evaluate whether they support such extraordinary conclusions.
I’m eager to follow the progress of this story as more of the results are released and analyzed by the scientific community.
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In 2011, an excavator operator working in a Canadian mine uncovered a group of unusual looking rocks. The rocks turned out to be the remains of a dinosaur called a nodosaur that died about 110 million years ago. The nodosaur was so well preserved that it looks like a stone statue of a dinosaur instead of just fossilized remains.
The more I look at it, the more mind-boggling it becomes. Fossilized remnants of skin still cover the bumpy armor plates dotting the animal’s skull. Its right forefoot lies by its side, its five digits splayed upward. I can count the scales on its sole. Caleb Brown, a postdoctoral researcher at the museum, grins at my astonishment. “We don’t just have a skeleton,” he tells me later. “We have a dinosaur as it would have been.”
The photos are amazing…it really does look like a statue.
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The Paleobiology Database Navigator is a world map that shows where hundreds of thousands of fossils have been found. The data is maintained by an international group of paleontologists and you can filter the map by type of fossil and when it was found. There’s even a toggle to flip back and forth between the current placement of the continents and much earlier Pangea-like configurations. (via @srikardr)
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Paleontologist Lida Xing found the feathered tail of a tiny dinosaur trapped in a piece of amber for sale at a market in Myanmar.
As soon as Xing saw it, he knew it wasn’t a plant. It was the delicate, feathered tail of a tiny dinosaur.
“I have studied paleontology for more than 10 years and have been interested in dinosaurs for more than 30 years. But I never expected we could find a dinosaur in amber. This may be the coolest find in my life,” says Xing, a paleontologist at China University of Geosciences in Beijing. “The feathers on the tail are so dense and regular, this is really wonderful.”
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There’s a new king of the dinosaurs: Dreadnoughtus schrani. A skeleton of the species was unearthed in Argentina in 2005 and the results of the recently released analysis show this Dreadnoughtus was 85 feet long, weighed around 65 tons, and had a powerful “weaponized tail”. The kicker? It was not yet an adult and still growing when it died.
While other giants from Patagonia are known from a handful of bones, almost half of the Dreadnoughtus skeleton has been recovered. What’s more, the fossilised bones are in such good condition — even revealing where muscles attached — that the skeleton could provide unprecedented insights into the biology, movement and evolution of the group of huge plant-eating dinosaurs it belonged to, called the titanosaurian sauropods.
By comparison, an Apatosaurus (née Brontosaurus) is ~75 feet long and weighed 22 tons while a Boeing 737-900 weights around 50 tons. Here’s some more background on the Dreadnoughtus and a video showing some of the fossils:
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An Elvis taxon is the apparent rediscovery of an animal that has vanished from the fossil record, but that is really the discovery of a look-alike animal. “The term Elvis taxon is used because of the large number of sightings of Elvis Presley long after his death, as well as for his many impersonators.”
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