A class of marine animals known as cephalopods – which today includes squid, octopus and cuttlefish – could have existed on Earth 30 million years earlier than previously thought, according to new research.
Moreover, if we need to reset the time of the appearance of cephalopods, then we may need to re-examine the entire evolutionary history of invertebrates, given the importance of these creatures in the overall picture of life on the planet.
The key to the new research is the discovery of several 522-million-year-old cone-shaped fossils on the Avalon Peninsula in Newfoundland, Canada, that contain certain characteristics of control signs that mean they could be classified as cephalopods.
“If these were actually to be cephalopods, we would have to date the origins of cephalopods to the early Cambrian period,” says geoscientist Anne Hildenbrand of Germany’s Heidelberg University.
“That would mean that cephalopods appeared at the very beginning of the evolution of multicellular organisms during the Cambrian explosion.”
Until now, they were thought to be the earliest cephalopods Plectronoceras cambria – tiny mollusks with cone-like shells that lived in the late Cambrian period, approximately 490 million years ago.
Although our knowledge of P. cambriaThe anatomy is based on incomplete fossils, these new findings are similar enough to suggest a link between the species. They are also different enough to support the hypothesis that millions of years of evolution could separate them.
For example, one of the characteristics scientists have observed in several Cretaceous shells from the Avalon Peninsula is evidence of sifuncula: a tissue tube that helps drain water from the shell, manage nitrogen, oxygen and carbon dioxide levels, and control buoyancy.
However, signs of sifuncle are not present on all newly found fossils, and its position is slightly different from where it would be expected. After a thorough analysis of these similarities and differences, the researchers think they have come across fossils that are indeed an older form of cephalopods.
“The presence of sifuncules, septal necks, and a connecting ring are usually considered key characteristics to distinguish early fossil cephalopods from other septate or ventricular organisms,” the researchers write in their paper.
“However, some authors have also assigned fossil shell material to cephalopods that lacks these properties.”
Adjusting the timeline would mean that cephalopods formed before certain euarthropods (including insects and crustaceans), which originate from the terrain part of the geological record.
As the first organisms to be able to move up and down in water – thanks to another siphon – and settle in the open ocean, cephalopods play an important role in early evolutionary history, so experts want to pinpoint their timing.
Classifying creatures can often be a tricky endeavor, even when we’re not talking about fossilized remains more than half a billion years old, but researchers hope further research and further discoveries will help verify their claims. A hunt is underway to find better preserved specimens from the same area.
“This discovery is extraordinary,” says geoscientist Gregor Austermann of the University of Heidelberg. “It has long been suspected in scientific circles that the evolution of these highly developed organisms began much earlier than previously thought. But there was a lack of fossil evidence to support this theory.”
The research was published in Communication biology.