Estimates of the origin of modern octopuses have been pushed back tens of millions of years following the discovery of three new species of fossil octopus, identified from five beautifully preserved specimens. Sarah Day reports.
The octopus has long presented a puzzle for scientists interested in evolutionary history. Lacking a well-developed skeleton, they are composed almost entirely of muscle and skin. When an octopus dies, it quickly decays and becomes little more than a slimy blob. Often, carcases don’t make it this far, but are consumed by scavengers shortly after death.
As a result, the octopus fossil record is virtually non-existent. Until now, none of the 200-300 present day species of octopus has ever been found in fossilized form, and only a single species was known.
The new specimens, described in the latest issue of Palaeontology, were discovered in Cretaceous rocks in Lebanon and dated to 95 million years old. They show an astonishing degree of preservation, recording the octopus’ eight limbs with traces of muscles and rows of suckers. Some specimens even contain traces of ink and internal gills.
‘They are sensational fossils, extraordinarily well preserved’, says Dirk Fuchs of the Freie University of Berlin, lead author of the report. They have been preserved by compression on the surface of the limestone, leaving behind imprints of their soft parts. Some parts were mineralised after death in whitish-yellow apatite (calcium phosphate).
The fossils show a surprising similarity to modern day octopuses, providing important information about their evolutionary history. ‘These things are 95 million years old’, says Dr Fuchs, ‘yet one of the fossils is almost indistinguishable from living species. The more primitive relatives of octopuses had fleshy fins along their bodies. The new fossils are so well preserved that they show, like living octopus, that they didn’t have these structures’.
Such soft-body preservation is so rare that Mark Purnell, for the Palaeontological Association, remarked that finding an octopus as a fossil “is about as unlikely as finding a fossil sneeze”.
Estimates as to the origins of modern octopuses have now been pushed back by tens of millions of years, thanks to the discovery of these rarest and unlikeliest of fossils.