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But a
sophisticated skull analysis showed that this reptile called
Eunotosaurus africanus that lived in southern Africa 260 million
years ago is actually the earliest-known turtle, even though it
had no shell, researchers said on Wednesday.
Eunotosaurus, about a foot (30 cm) long, possessed wide and flat
ribs that gave it a distinctly rounded and turtle-like profile.
It mixed features of its lizard-like ancestors with emerging
turtle-like characteristics that evolved over tens of millions
of years into familiar turtle traits, the researchers said.
"Think of your neighborhood box turtle, but much more flattened
and with scaly skin and a long tail," said New York Institute of
Technology anatomy professor Gaberiel Bever, describing
Eunotosaurus. "And teeth, it had a mouthful of them."
Only later did turtles become toothless.
Eunotosaurus lived during the Permian Period 20 million years
before Pappochelys, a creature from Germany that in June was
identified as the earliest-known turtle, and 30 million years
before the first dinosaurs. The earliest-known turtle with a
fully formed shell lived around 210 million years ago.
Eunotosaurus fossils were first unearthed in South Africa in the
late 19th century. There has been a long debate about whether it
was part of the turtle lineage.
Bever's team used advanced scanning technology to perform a
detailed analysis of its skull anatomy, digitally dissecting
each cranial bone in four fossil specimens, to help demonstrate
Eunotosaurus was the oldest-known member of the turtle group.
"Where turtles came from, evolutionarily speaking, and how they
are related to the other major groups of living reptiles -
lizards, snakes, crocodiles and birds - has been a topic of
vigorous debate for as long as we've had a theory of evolution,"
Bever said.
Fresh insight into the turtle lineage came in 2008 when
scientists described a primitive turtle from 220 million years
ago called Odontochelys from China.
"Turtles have been missing their Archaeopteryx, their missing
link to the rest of the vertebrate tree, since Darwin told us
that we should be looking for one," said Bever, mentioning the
oldest-known bird.
"With Odontochelys, Pappochelys and now Eunotosaurus, we now
have a remarkable series of transitional forms that take us from
an almost lizard-like creature to the modern turtle body plan
that is so interesting and bizarre."
The research appears in the journal Nature.
(Reporting by Will Dunham; Editing by Sandra Maler)
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