Fossil of worlds oldest plant-eating lizard could shed light on evolutionary puzzle

March 25th, 2008 - 1:09 pm ICT by admin  

National Geographic

Washington, March 25 (ANI): Scientists have discovered a rare fossil in Japan that belongs to the worlds oldest plant-eating lizard, which could shed light on an evolutionary puzzle that Charles Darwin described as an “abominable mystery.

According to a report in National Geographic News, the 130-million-year-old jaw and skull bones were unearthed in the Ishikawa Prefecture of Japan.

Based on the size of the skull, the researchers estimate that the lizard measured between 10 to 12 inches (25 to 30 centimeters) in length.

Prior to the new discovery, the oldest known plant-eating lizard was Dicothodon, which lived in North America about 100 million years ago.

Even today, fully herbivorous, or plant-eating, lizards are rare, with only about 3 percent of modern lizards belonging to the group. Most lizards eat flesh, usually insects, or a combination of flesh and plants.

Modern herbivorous lizards eat flowering plants, or angiosperms, whose buds and leaves are typically softer than nonflowering plants.

Thus the new fossil species, dubbed Kuwajimalla kagaensis, could indicate that angiosperms were already in existence and perhaps widespread millions of years earlier than had been thought, according to the researchers.

“By finding this particular fossil from Japan, it might suggest that flowering plants were already there, but we don’t have direct evidence yet,” said study team member Makoto Manabe of Japan’s National Science Museum in Tokyo.

Currently, the oldest evidence of a flowering plant is a 125-million-year-old fossil from China.

The apparently sudden appearance of angiosperms in the fossil record confounded Darwin, who worried that it might pose a problem for his theory of evolution by natural selection.

Scientists have since uncovered fossils tracing the evolution of angiosperms from nonflowering plants, called gymnosperms.

The K. kagaensis fossil was unearthed in 2001, but it was only with recent analysis by Manabe and Susan Evan, a paleontologist at the University College London, that its significance was realized.

According to Christopher Austin, a herpetologist and curator at Louisiana State University’s Museum of Natural Science, the fossil discovery is a “spectacular” find that challenges long-held views about lizard evolution.

“The ancestral condition for lizards has always been assumed to be insectivorous (insect-eating), so this new fossil provides data that challenges this thinking,” he said.

Austin added that the anatomical features of Kuwajimalla kagaensis suggest “that either the ancestral condition for lizard diet was not as restricted as once thought or that diet has been highly labile (easily changed) throughout lizard evolution.” (ANI)

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