For the roughly 300 known octopus species dwelling in the world's oceans, having eight arms is a defining characteristic. But that is not the way it started.
Scientists said on Tuesday a fossil unearthed in central Montana of a species named Syllipsimopodi bideni represents the oldest-known relative of today's octopuses and boasts 10 arms, with two twice as long as the other eight. The fossil, so well preserved that it reveals two parallel rows of suckers up and down each arm, dates to about 328 million years ago.
"Octopuses are the most intelligent invertebrates, and among the most intelligent animals overall. It is fascinating to see what these unique animals started from evolutionarily," Whalen said. Today's vampire squids have eight arms and two thin filaments that scientists long have considered vestiges of former arms. Octopuses do not have these vestigial filaments.
"Capture of prey is facilitated by the two longer tentacles with the eight shorter arms helping to manipulate the prey and transport it to the beak," said study co-author Neil Landman, an American Museum of Natural History invertebrate paleontologist.