May 24, 2012

First Land Animal Didn’t Walk On Land Using Four Legs

Lee Rannals for RedOrbit.com

Scientists say that the 360-million-year-old animal that was first to have moved around on land did not do so using four legs.

Images have shown that Ichthyostega walked on land similar to how a salamander walks around today, but 3D computer models have led scientists to disagree.

According to a study published in the journal Nature, Ichthyostega would have actually transported from water using its front limbs as crutches.

The animal lived during the Upper Devonian period and has been dubbed a "fishapod," because of its mixture of fish-like and amphibious features.

A team from The Royal Veterinary College, London and the University of Cambridge spent three years reconstructing the first 3D computer model of Ichthyostega from fossils.

"It took almost three years of hard work on difficult fossil material but we are finally able to see how the skeleton of Ichthyostega fits together and might have moved in three dimensions," Dr. Stephanie Pierce, study author, said in a press release. "This is very exciting as it allows us to examine how ancient vertebrates made the monumental transition from swimming to walking."

They were able to study how ancient vertebrates made the "monumental transition" from swimming to walking.

The team said the 3D skeleton allowed the researchers to calculate the range of movement in the joints of Ichthyostega's limbs.  Each bone was carefully put together like a jigsaw puzzle in animation software, and manipulated to estimate each joint's maximal range of motion.

"Our reconstruction demonstrates that the old idea, often seen in popular books and museum displays, of Ichthyostega looking and walking like a large salamander, with four sturdy legs, is incorrect,” Professor Jennifer A Clack from the University of Cambridge said in a press release.

The researchers said Ichthyostega would have actually moved around on land similar to how mudskippers maneuver today.

"The limbs of Ichthyostega probably would have behaved in a similar way, i.e. the forelimbs would have pushed the body up and forward while the hindlimbs and tail trailed behind," the researchers wrote in a press release.

They said this type of locomotion in the earliest limbed animals helped to stabilize the body during their first "steps" onto land.

The researchers said they are now working on investigating how the vertebral column of Ichthyostega and its relatives was constructed, as well as how it might have moved.


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