Finding a radula, the chitinous, toothed, conveyor-belt-like tongue used by mollusks to scrape food, was the definitive proof that Pohlsepia was indeed a mollusk. A more precise answer came in the form of the teeth. The synchrotron scan was sharp enough to let researchers count the tiny, individual tooth impressions across the radula\u2019s transverse rows. They observed a central rachidian tooth, pairs of lateral teeth, marginal teeth, and smooth marginal plates, adding up to at least 11 distinct elements per row. The only animals matching this exact 11-element configuration are Nautiloids, ancient, shelled relatives of modern cephalopods.<\/p>\n
\u201cPohlsepia mazonensis is a nautiloid that died, decomposed, lost its protective shell and was subsequently flattened into the mud and preserved as an ambiguous stain,\u201d Clements said.<\/p>\n
Switching titles<\/p>\n
But while the fossil\u2019s \u201coldest octopus\u201d badge is most likely gone, it managed to earn itself some new superlatives. \u201cThe first is of course the most difficult fossil to work on that I\u2019ve ever worked on,\u201d Clements said. \u201cThe second would probably be the most fun fossil I\u2019ve ever worked on.\u201d<\/p>\n
The results of his study also made Pohlsepia the oldest unequivocal piece of evidence of nautiloid soft tissues ever found in the entire Paleozoic fossil record. \u201cI\u2019d say unequivocal because other nautiloid soft tissue fossils are a bit questionable,\u201d Clements said.<\/p>\n
His team now plans to use the same advanced imaging on other fossils. \u201cMazon Creek in particular is full of very interesting and very weird fossils which have not been looked at for a long time, and you know, all of these new techniques can be used on them,\u201d Clements said.<\/p>\n
He thinks that even for Pohlsepia itself, it\u2019s not yet the end of the story. \u201cIt\u2019s the oldest nautiloid now, so it would be interesting to study it more.\u201d<\/p>\n