The muscle arrangement of an ancient fish may have included abdominal muscles, previously thought to be only found in land animals, an international team of paleontologists said.

The scientists recently published their study in the journal Science on the preserved tissue found in the fossils of an ancient armored fish called a placoderm and managed to map its muscle arrangements.

The study’s coauthor, professor Kate Trinajstic of Curtin University in Australia, told the media that she was “stunned” to find abdominal muscles in the placoderm.

“Abdominal muscles were thought to be an invention of animals that first walked onto the land but this discovery shows that these muscles appeared much earlier in our evolutionary history,” Trinajstic was quoted as saying. Abdominal muscles in land animals usually protect internal organs and provide postural and movement support.

Along with complex muscle system unlike any other known modern fish, the prehistoric fish also had a differentiated vertebral column, which is “quite an advanced feature,” she told a U.S. broadcaster. She said discovery of the fossils tells us “primitive doesn’t mean simple.”

Placoderms are thought to have first emerged during the late Silurian, and prospered during the Devonian Period. The fossil used in the study is 380 million years old and has the oldest known fossilized vertebrate muscles.

The new discovery is expected to provide scientist clues about vertebrate and muscle evolution in the earliest jawed animals.

(khnews@heraldcorp.com)