Eight BC

Extremely rare fossils of ancient octopuses have been found in Lebanon

Noam Levithan and Yonat Ashhar Galileo

Fossils - the remains of ancient organisms - can only form under special conditions, which usually do not exist. One of the conditions that can help to create fossils is the presence of hard body parts, such as bones or shells, in the fortification of the appetizer as well as a maddening protection of the carcass and its decomposition. Even rarer fossils are fossils in which soft tissues have been preserved. Sometimes an organism without hard body parts leaves a pattern, an imprint, of its body in the rock, but very rarely the soft body tissues are preserved after being replaced by minerals. Fossils of this rare type were recently discovered by Dirk Fuchs from the Free University of Berlin and his colleagues, in limestone rocks in Lebanon, at a site located approximately 45 km from Beirut and 15 km from Jebel. The fossils are of three species of octopuses that lived about 95 million years ago. The finding was published in the scientific journal palaeontology.

Octopuses are mollusks and have almost no hard body parts. When an octopus dies, its soft tissues rot quickly and usually no trace of it remains. Thus, even though the octopus species are extremely diverse and there are more than 300 different species of them today, until now only a single fossilized ancient octopus species was known. Fortunately, when the octopuses found in Lebanon died, they quickly sank to the oxygen-poor seabed and were covered in sediment without rotting. Because of this, well-preserved fossils were obtained, whose soft tissues turned into a yellowish-white mineral apatite (calcium phosphate).

When you look at these fossils you can immediately notice how similar they are to contemporary octopuses: they have a sack-like body and head with eight arms attached to the front end (hence the name of the class to which octopuses and their relatives belong: cephalopods) and on the arms are rows of snap buttons. In the fossils it is also possible to distinguish remains of muscles, gills, the ink sac and even the ink itself that leaked out of the sac.

Although the shape of fossil octopuses resembles the octopuses we know today, not every eight-armed cephalopod is a modern octopus, just as not every four-legged, tailed mammal is a rhinoceros. Thanks to the excellent state of preservation of the octopuses that were discovered, it is possible to distinguish that they are indeed not contemporary octopuses, but rather represent a transitional form between the ancestor of octopuses and the common octopus species today.

One of the prominent features, different from the ancient octopuses, is the remains of the shell. Many molluscs have a shell, but it has degenerated in octopuses and their close relatives, squid. In the case of the squids, a sort of tiny plate remained from the shell inside their body, while in the octopuses the shell degenerated even more, until all that remained of it was a pair of tiny, rod-like internal structures. The disappearance of the shell is what enables the impressive and famous flexibility of modern octopuses.

The findings that the researchers discovered in these rare fossils, and the differences between the fossilized octopuses and their contemporaries, allowed the researchers to learn more details about the evolution of octopuses, about which so little is known. Their conclusion was that the inner shell of the ancestors of the octopuses was cut during evolution into a pair of calluses that moved away from each other, degenerated into a pair of rods and continued to degenerate until the structures present in modern octopuses. The discovery of the fossils also revealed that despite the fact that 95 million years ago there were octopuses with relatively large shell remains, octopuses that apparently were not the ancestors of the modern octopuses but represent an ancient state, there existed at the same time octopuses (such as the third species described) with structures reminiscent of modern octopuses , and apparently they were their ancient ancestors.

The original article:

Fuchs, D., Bracchi, G. & Weis, R. New octopods (Cephalopoda: Coleoidea) from the late Cretaceous (Upper Cenomanian) of Hâkel and Hâdjoula, Lebanon. palaeontology 52, 65-81 (2009). doi: 10.1111/j.1475-4983.2008.00828.x

The original article appears in the Galileo magazine issue 129, May 2009