522 29 OCTOBER 2021 • VOL 374 ISSUE 6567 science.org SCIENCEBut despite its reputation as a “dino
killer,” a few paleontologists have raised
the possibility that the dinosaurs were al-
ready extinct or in serious decline when the
asteroid struck. They say dinosaur fossils
are rare in deposits 3 meters or so immedi-
ately below the thin line of clay, rich in the
metal iridium—abundant in asteroids—
that marks the impact in rock outcrops
around the world. These scientists suggest
nonbird dinosaurs had perished 1 million
or so years before the impact, perhaps in
the wake of bursts of volcanism.
In 2019, DePalma, then a paleontology
graduate student at the University of Kan-
sas, Lawrence, and colleagues published
a paper in the Proceedings of the National
Academy of Sciences (PNAS) on the Tanis
site. They reported finding glassy debris
formed by the intense heat of the asteroid’s
impact buried directly alongside and inside
of fossilized fish. Tanis, in the Hell Creek
formation, was once located on a riverbank,
and the researchers claimed the fossil as-
semblage represented a burial ground for
animals swept up the river valley and killed
by surging waters in the minutes and hours
following the impact. The paper said noth-
ing about dinosaurs, however.
A few days before the PNAS paper went
online, The New Yorker published an ar-
ticle about the site, describing fossils of
dinosaur skin and feathers not mentioned
in the PNAS paper. In the magazine ar-
ticle, DePalma and colleagues said this
suggested dinosaurs were thriving until
the asteroid’s impact. But some paleonto-
logists, noting that they couldn’t evaluate
evidence given only in the magazine, pro-
fessed skepticism. (DePalma says earlier
drafts of the PNAS paper had included
dinosaur data that were removed during
later editing rounds.)
Last week, more than 2 years after that
kerfuffle, DePalma, now working toward a
Ph.D. at the University of Manchester, and
colleagues finally presented dinosaur data.
One talk, presented by DePalma’s colleague
Riley Wehr, a geosciences graduate student
at Florida Atlantic University, described
fossilized bones and a piece of remark-
ably well preserved bumpy skin identified
as likely belonging to a Triceratops. These
fossils came from the same layers that ap-
peared to record the sedimentary surge
that buried the fish. The partially decayed
skin indicated the animal had died a few
weeks before the impact, Wehr noted.
He also described 11 feathers in the surge
deposit that he said were larger than those
of any known bird from the Hell Creek
formation. “The feathers either came from
a dinosaur or a currently unknown bird
taxon,” he said.
Wehr presented some evidence not men-
tioned in The New Yorker: In a layer of clay
immediately below the impact layer, the
researchers report several fossilized foot-
prints they say most likely came from an in-
fant Triceratops, infant and adult footprints
from hadrosaurs, and several less-distinctive
tracks attributed to the broad group of car-
nivorous dinosaurs called theropods. “The
dinosaur trackways at Tanis do represent a
rich and taxonomically diverse dinosaurian
assemblage which immediately precedes the
impact,” Wehr said in his talk. They reveal “a
thriving dinosaurian community,” he added.
DePalma says there’s no reason to believe
these dinosaurs were hanging on long after
dying out elsewhere. “It would really shock
and surprise me if the Hell Creek formation
was [the] only, last isolated nugget of vibrant
life before the impact occurred.” A paper de-
scribing the dinosaur finds is in review at a
journal and a few others are being prepared
for submission, he adds.
After the haze of skepticism that followed
the New Yorker article, Gulick says he’s glad
to see the research presented to a scientific
audience, with peer-reviewed papers on the
way. He says he reviewed the original Tanis
paper in PNAS and that “some of what didn’t
end up in that article ... was not quite ready
for primetime ...[and] needed more work.
Now more work has been done and has
started to come out and that’s great.”
The proximity of the fossils and footprints
to the Cretaceous-Paleogene boundary “in-
deed supports the idea that dinosaurs were
still present in North America at the time
of the Chicxulub impact,” says Philippe
Lambert, an astrogeologist and director of a
research institute that studies an impact cra-
ter at Rochechouart in France.
But Behrensmeyer, an expert on fossil
preservation, says the researchers haven’t
shown enough evidence the tracks were
made shortly before the impact. The flood-
water surge may have eroded away a layer
of sediment, revealing older trackways in an
underlying rock layer. She thinks DePalma
and colleagues have more work to do. “Be-
cause of early polarization caused by The
New Yorker article, it will take a hypothesis-
testing approach and extra attention to de-
tail in future manuscripts ... to convince the
community,” she wrote in an email.
Steve Brusatte, a paleontologist at the
University of Edinburgh, says the evidence
from Tanis is “remarkable,” but he, too, is
waiting to see whether the dating of the
various fossils, feathers, and trackways
holds up. “If the dating is solid, then this
is a remarkable story, and it proves that
dinosaurs were thriving in western North
America right up until the asteroid fell from
the sky.” jPandemic
spotlight brings
attention—and
plenty of heat
Scientists like Devi
Sridhar leaped to fill an
information gap
THE NEW NORMALBy Kai KupferschmidtC
OVID-19 catapulted Devi Sridhar to a
stardom she could scarcely have imag-
ined. Two years ago, she was an accom-
plished academic, studying disease
outbreaks in Brazil, India, and Haiti
and running the Global Health Gover-
nance Programme at the University of Edin-
burgh. Sridhar, who is 37, was media savvy;
she had co-authored a book with Chelsea
Clinton and often spoke on global health. But
as COVID-19 exploded, the spotlight shone
far brighter: She began advising the Scottish
government on pandemic policies, appear-
ing regularly on U.K. morning TV shows, and
writing a weekly column for The Guardian.
She has a book on the pandemic coming
out next spring and has amassed more than
300,000 followers on Twitter.
Sridhar is one of dozens of researchers,
many in fields like epidemiology, virology,
and global health that previously drew little
public interest, who became famous almost
overnight when they took to social media to
comment on pandemic policies and science.
“He’s real and he’s spectacular!” cheered
Savannah Guthrie, co-host of The Today
Show, in reference to a legendary Seinfeld
episode, after interviewing Ashish Jha, dean
of the Brown University School of Public
Health. In Germany, virologist Christian
Drosten has four times as many Twitter
followers—800,000—as the likely next leader
of his country, Olaf Scholz. “For the tin foil
hats I’m an annoyance, for everyone else the
Chuck Norris of science,” rocked the skate
punk band ZSK, in a tribute song to Drosten.
These scientist-personalities are navigat-
ing their fame with a mix of enthusiasm, anx-
iety, exhaustion—and uncertainty about what
their future professional lives will look like.
“The anonymity of just being able to kind of
do my stuff is gone,” says Sridhar, who’s been
greeted by a Twitter follower in a yoga class.NEWS | IN DEPTH