A 300 million-year-old ten-armed octopus fossil has been unearthed in the United States. The fossil, dubbed Syllipsimopodi bideni after US President Joe Biden, is likely to be the oldest known ancestor of vampire squid and octopus.

The ancient progenitors of the group of animals that includes octopuses and vampire squids had not eight, but ten arms, according to new research undertaken by scientists at the American Museum of Natural History and Yale University.

The study, which defines a new species of vampyropod based on a previously unknown 328-million-year-old fossil, stretches the group’s age back nearly 82 million years.

The findings were published in Nature Communications today.

Vampyropods are soft-bodied cephalopods with eight arms and chitinous shell or fin supports that are internalized. Vampyropoda is poorly recorded in the fossil record due to its lack of hard features. The new research is based on an extremely well-preserved vampyropod fossil from the Royal Ontario Museum’s collection (ROM). ROM received it in 1988 after it was discovered in what is now Montana.

The fossil specimen was identified by Whalen and coauthor Neil Landman, a curator emeritus in the Museum’s Division of Paleontology, as a completely new genus and species dating to around 328 million years old, making it the oldest known vampyropod and extending the group’s fossil record by about 82 million years. Moreover, they also describe its ten arms in the current study, all of which have retained suckers, confirming prior scientific claims that the common ancestor of vampyropods had ten arms as well.

“The arm count is one of the defining characteristics separating the 10-armed squid and cuttlefish line (Decabrachia) from the eight armed octopus and vampire squid line (Vampyropoda). We have long understood that octopuses achieve the eight arm count through elimination of the two filaments of vampire squid, and that these filaments are vestigial arms,” explains Whalen.  

“However, all previously reported fossil vampyropods preserving the appendages only have 8 arms, so this fossil is arguably the first confirmation of the idea that all cephalopods ancestrally possessed ten arms.”

Two of the cephalopod’s limbs appear to be longer than the other eight, and its torpedo-shaped body appears similar to that of modern squids. Syllipsimopodi bideni was the name given to the fossil. Because this is the first known cephalopod to grow suckers, which allow the arms, which are modifications of the molluscan foot, to better grab prey and other things, the genus name is derived from the Greek words “syllpsimos” for “prehensile” and “pódi” for “foot.” The species name is in honor of Joseph R. Biden, the 46th President of the United States, who was recently inaugurated (at the time of paper submission).

“Syllipsimopodi may have filled a niche more similar to extant squids, a midlevel aquatic predator,” adds Landman. “It is not inconceivable that it might have used its sucker-laden arms to pry small ammonoids out of their shells or ventured more inshore to prey on brachiopods, bivalves, or other shelled marine animals.”

Based on the age, characters, and phylogenetic position, the fossil challenges the predominant arguments for vampyropod origins, and the authors propose a new model for coleoid (internally shelled cephalopod) evolution. 

Source: 10.1038/s41467-022-28333-5

Image Credit: Getty /  © K. WHALEN

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