66 DISCOVERMAGAZINE.COM
TOP: MAGGIE NEWMAN. BOTTOM: R. GESS ET AL./SCIENCE JUNE 8, 2018Polar Fossils
Challenge Ideas
About Early Life
on Land
A roadwork salvage project has
rewritten the story of the earliest
land vertebrates, ancestors
of everything from dinosaurs
to primates.
The irst four-limbed vertebrates,
or tetrapods, climbed out of the sea
and onto land more than 365 million
years ago. They’re known from
mostly fragmentary inds in
ancient tropical environments,
almost entirely in the Northern
Hemisphere, which led researchers
to believe that our distant ancestors
evolved in warm estuaries at or just
north of the equator.
Well, maybe not.
Aware that a portion of a
local fossil site was about to be
demolished in road construction,
Robert Gess, a paleontologist at
South Africa’s Albany Museum,
gathered a team to save about
100 tons of rock that he has stored
in sheds for more than a decade. As
time permits, he splits open pieces
of the shale, a fossil-rich type ofrock formed from layers of mud.
Only about 20 percent through
the stockpile, he found two new
tetrapods that are approximately
360 million years old.
What’s most signiicant about
the animals, described in June in
Science, is that at the time they
lived, that part of modern South
Africa was a lot farther from the
equator. The site was actually
within the Antarctic Circle, making
the animals the irst known ancient
polar tetrapods.
“There was an assumption that
what was driving [tetrapod]
evolution was something
to do with tropical
conditions,” says Gess.
“The new discoveries
completely disrupt
this belief system,
illustrating
that by
this stage,tetrapods lived all over the world,
right down into the Antarctic
Circle. It completely opens up the
possibilities as to where tetrapods
may have originated and therefore
under what climatic conditions.”
Gess continues to split the
salvaged shale whenever time
allows, looking for the next
surprise. He’s also reconstructing
the site’s entire ancient ecosystem,
including a large predatory ish
he calls “probably the biggest
existential threat to the tetrapods.”
Perhaps most tantalizing,
the shale has also yielded ish
fossils with excellent soft tissue
preservation. Because the rock
formed from ine-grained mud at
the oxygen-starved bottom of a
brackish body of water, “anything
that was well buried,” says Gess,
“could be preserved whole.”
Imagine: an entire early tetrapod.
Keep splitting, Rob.PALEONTOLOGY
Waterloo Farm, a site in South Africa that has yielded multiple fossils, was a brackish
estuary about 360 million years ago, home to at least two four-limbed vertebrates called
tetrapods: Umzantsia (left, diving after a fish) and Tutusius (right, surfacing for a snack).
The tetrapods lived within the Antarctic Circle, challenging ideas about their evolution.The ancient supercontinent of Gondwana was centered around the
South Pole (P) about 360 million years ago. The black asterisk marks
the site of the new South African tetrapods, within the Antarctic Circle.30° S60° SAntarctic^ Circle