Fossil mystery solved: Super-long-necked reptiles lived in the ocean,
not on land
Twenty-foot-long specimens described as separate species from their
cousins, named after mythology's Hydra

Date:
August 6, 2020
Source:
Field Museum
Summary:
By CT scanning crushed fossilized skulls and digitally
reassembling them, and by examining the fossils' growth rings,
scientists were able to describe a new species of prehistoric sea
creature. Tanystropheus hydroides, named after mythology's hydra,
was a twenty-foot-long animal with a ten-foot-long neck.



FULL STORY ==========================================================================
A fossil called Tanystropheus was first described in 1852, and it's been puzzling scientists ever since. At one point, paleontologists thought it
was a flying pterosaur, like a pterodactyl, and that its long, hollow
bones were phalanges in the finger that supported the wing. Later on,
they figured out that those were elongated neck bones, and that it was
a twenty-foot-long reptile with a ten-foot neck: three times as long
as its torso. Scientists still weren't sure if it lived on land or in
the water, and they didn't know if smaller specimens were juveniles or
a completely different species -- until now. By CT-scanning the fossils' crushed skulls and digitally reassembling them, researchers found evidence
that the animals were water-dwelling, and by examining the growth rings
in bones, determined that the big and little Tanystropheus were separate species that could live alongside each other without competing because
they hunted different prey.


========================================================================== "I've been studying Tanystropheus for over thirty years, so it's extremely satisfying to see these creatures demystified," says Olivier Rieppel,
a paleontologist at the Field Museum in Chicago and one of the authors
of a new paper in Current Biology detailing the discovery.

Tanystropheus lived 242 million years ago, during the middle Triassic. On
land, dinosaurs were just starting to emerge, and the sea was ruled by
giant reptiles. For a long time, though, scientists weren't sure whether Tanystropheus lived on land or in the water. Its bizarre body didn't
make things clear one way or the other.

"Tanystropheus looked like a stubby crocodile with a very, very long
neck," says Rieppel. The larger specimens were twenty feet long, with
their necks making up ten feet of that length. Oddly for animals with
such long necks, they only had thirteen neck vertebrae, just really
elongated. (We see the same thing with giraffes, which have only seven
neck bones, just like humans.) And their necks were rather inflexible, reinforced with extra bones called cervical ribs.

In the same region where many of the big Tanystropheus fossils were found,
in what's now Switzerland, there were also fossils from similar-looking
animals that were only about four feet long. So not only were scientists
unsure if these were land-dwellers or marine animals, but they also didn't
know if the smaller specimens were juveniles, or a separate species from
the twenty- footers.

To solve these two long-standing mysteries, the researchers used
newer technologies to see details of the animals' bones. The large Tanystropheus fossils' skulls had been crushed, but Stephan Spiekman,
the paper's lead author and a researcher at the University of Zurich,
was able to take CT scans of the fossil slabs and generate 3D images of
the bone fragments inside.



==========================================================================
"The power of CT scanning allows us to see details that are otherwise impossible to observe in fossils," says Spiekman. "From a strongly
crushed skull we have been able to reconstruct an almost complete 3D
skull, revealing crucial morphological details." The skulls had key
features, including nostrils on top of the snout like a crocodile's,
that suggested Tanystropheus lived in the water. It probably lay in wait, waiting for fish and squid-like animals to swim by, and then snagged
them with its long, curved teeth. It may have come to land to lay eggs,
but overall, it stayed in the ocean.

Rieppel wasn't surprised that evidence pointed to a water-dwelling Tanystropheus. "That neck doesn't make sense in a terrestrial
environment," he says. "It's just an awkward structure to carry around."
So that answered one question, about where Tanystropheus lived. To learn whether the small specimens were juveniles or a separate species, the researchers examined the bones for signs of growth and aging.

"We looked at cross sections of bones from the small type and were very
excited to find many growth rings. This tells us that these animals were mature," says Torsten Scheyer, the study's senior author and a researcher
at University of Zurich.



==========================================================================
"The small form is an adult, which basically sealed the case," says
Rieppel.

"It's proven now that these are two species." The researchers named
the larger one Tanystropheus hydroides, after the long-necked hydras in
Greek mythology.

The small form bears the original name Tanystropheus longobardicus.

"For many years now we have had our suspicions that there were two
species of Tanystropheus, but until we were able to CT scan the larger specimens we had no definitive evidence. Now we do," says Nick Fraser,
Keeper of Natural Sciences at National Museums Scotland and a co-author
of the paper. "It is hugely significant to discover that there were two
quite separate species of this bizarrely long-necked reptile who swam
and lived alongside each other in the coastal waters of the great sea
of Tethys approximately 240 million years ago." The animals' different
sizes, along with cone-shaped teeth in the big species and crown-shaped
teeth in the little species, meant they probably weren't competing for
the same prey.

"These two closely related species had evolved to use different food
sources in the same environment," says Spiekman. "The small species
likely fed on small shelled animals, like shrimp, in contrast to the
fish and squid the large species ate. This is really remarkable, because
we expected the bizarre neck of Tanystropheus to be specialized for a
single task, like the neck of a giraffe.

But actually, it allowed for several lifestyles. This completely changes
the way we look at this animal." This "splitting up" of a habitat to accommodate two similar species is called niche partitioning. "Darwin
focused a lot on competition between species, and how competing over
resources can even result in one of the species going extinct," says
Rieppel. "But this kind of radical competition happens in restricted environments like islands. The marine basins that Tanystropheus lived in
could apparently support niche partitioning. It's an important ecological phenomenon." "Tanystropheus is an iconic fossil and has always been,"
adds Rieppel. "To clarify its taxonomy is an important first step to understanding that group and its evolution."

========================================================================== Story Source: Materials provided by Field_Museum. Note: Content may be
edited for style and length.


==========================================================================


Link to news story: https://www.sciencedaily.com/releases/2020/08/200806111849.htm

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