New discovery places turtles next to lizards on family tree

Jul 20, 2011

( -- Where do turtles belong on the evolutionary tree? For decades, the mystery has proven as tough to crack as the creatures' shells. With their body armor and retractable heads, turtles are such unique creatures that scientists have found it difficult to classify the strange animals in terms of their origins and closest relatives.

"We know turtles evolved from a along with birds, and snakes about 300 ago, but who modern-day turtles are most closely related to is one of the biggest and most controversial questions in the field of systematics," said Tyler Lyson, a Yale University graduate student who studies the between different .

Some researchers have analyzed turtles' genes and found they are most closely related to the group of animals that includes and birds. Others, comparing turtles' physical features to those of other reptiles, have placed them next to lizards or outside of the larger subclass of animals that includes lizards, crocodiles and birds altogether.

Now Lyson and his colleagues have used a novel approach involving microRNAs that strongly suggests turtles belong next to lizards.

Co-author Kevin Peterson, a paleobiologist at Dartmouth College, developed a technique to use microRNAs — small molecules that control gene activity and can switch certain genes on and off — to study evolutionary relationships. After discovering hundreds of microRNAs in the Carolina anole lizard, Peterson and co-authors then compared these to the microRNAs of a western painted turtle and an American alligator. The team found that four of the lizard's microRNAs were also present in the turtle, but were absent in birds, crocodiles and all other animals.

"Different microRNAs develop fairly rapidly in different animal species over time, but once developed, they then remain virtually unchanged," Peterson said. "They provide a kind of molecular map that allows us to trace a species' evolution."

The discovery, detailed online in Biology Letters, contradicts past studies that placed turtles next to crocodiles and birds rather than lizards. According to Lyson, those past findings were ambiguous and limited in scope, looking at just a few dozen genes, while the new technique analyzed all of the thousands of microRNAs found in turtles, lizards, and crocodiles.

"Our data unambiguously places turtles next to lizards," Lyson said. "But the data itself isn't infallible. We still need more data from these species in order to say definitely that and lizards are evolutionary cousins."

Next, the team plans to use its microRNA analysis on other animals to help determine their origins and relationships as well, and is developing a web-based platform to share the software with other researchers around the world.

Explore further: Rare Sri Lankan leopards born in French zoo

More information: Lyson, T. R. et al. Biology Letters doi:10.1098/rsbl.2011.0477 (2011).

Related Stories

Tough turtles survive cretaceous meteorite impact

Jul 12, 2011

( -- New fossil localities from North Dakota and Montana have produced the remains of a turtle that survived the 65 million-year-old meteorite impact that wiped out the dinosaurs. The resulting ...

Turtles caught in the cold to rehab

Dec 28, 2005

Ridley turtles and an 88-pound loggerhead turtle named Bruiser are expected to spend winter in rehabilitation in New York after being caught in the cold.

Recommended for you

'Killer sperm' prevents mating between worm species

17 hours ago

The classic definition of a biological species is the ability to breed within its group, and the inability to breed outside it. For instance, breeding a horse and a donkey may result in a live mule offspring, ...

Rare Sri Lankan leopards born in French zoo

20 hours ago

Two rare Sri Lankan leopard cubs have been born in a zoo in northern France, a boost for a sub-species that numbers only about 700 in the wild, the head of the facility said Tuesday.

Researcher reveals how amphibians crossed continents

22 hours ago

There are more than 7,000 known species of amphibians that can be found in nearly every type of ecosystem on six continents. But there have been few attempts to understand exactly when and how frogs, toads, ...

User comments : 5

Adjust slider to filter visible comments by rank

Display comments: newest first

not rated yet Jul 20, 2011
They certainly resemble a lizard with a shell!
1 / 5 (4) Jul 20, 2011
We know turtles evolved from a common ancestor along with birds, lizards and snakes about 300 million years ago

Just how DO they know this? Were they there all the time, watching these things evolve from a common ancestor? One needs to take such statements with a big grain of salt and a lot of gall. This is simply speculation of the highest order. But then the whole evolutionary theory is a big speculation anyway. Because these things have to do with origins - things that happened in the past - we cannot be certain that they did indeed happen as speculated. We can only take these things by faith.
Where are the missing links for instance that shows a lovely trail from the common ancestor to these current modern creatures? Yes, that's a cliche already but it still is a vexation of the first order - there are no undisputed missing links - even after millions of fossils [of completely fully formed creatures] have been found.
5 / 5 (2) Jul 20, 2011
Hey Kev - one thing about finding links along every single evolutionary branch. It requires well preserved fossils. More than that, The fossils have to be somewhere where people have already looked. Maybe the fossils are preserved that will provide all the links you think we need, but if they do still exist, then it means no one has yet looked in the correct place.

But it is not safe to assume that we will be able to find fossils of every stage of evolutionary development there are just not that many fossils.
not rated yet Jul 20, 2011

Just how DO they know this?

There are actually good, reasonable answers to this question. And if you had the slightest interest in actually learning something about the subject that you're always pretending authority on, you'd know that. Fercrissakes kev, get an education on the subject before you spout off. You know so little about it that you don't even realize how little you know. Or how moronic you sound.
not rated yet Jul 20, 2011
Kevinrts is actually an agent of the Devil.