Discovery of the oldest (living) ancestor of the “Vampire of the Abyss”, with 10 functional arms

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Vampires of the abyss, cephalopods essentially inhabiting the abyss, fascinate with their strange morphology. Rather widespread but little studied, their most distant ancestors would have populated our oceans since the Carboniferous (there is 350 at 300 million years). Recent studies then attempt to learn more about the superorder Vampyropods. By taking a closer look at an exceptionally well-preserved cephalopod fossil, recent research from the Manhattan Museum of Natural History (AMNH) has uncovered a startling discovery that may relate to the oldest ancestor of the deep-sea vampire and the octopus. Even more surprising, the specimen has ten tentacles instead of eight, and grows back almost 100 million years the age of the group. A discovery that completely changes the understanding of the evolution of this group of species.

Baptized Syllipsimopodi bideni, the famous specimen was named in l honor of the last President of the United States, Joe Biden. The fossil was apparently originally discovered in the years 80, in a Lagerstätte (sedimentary deposit containing very complete fossils) at Bear Gulch, Montana (United States). It has since been shelved, until AMNH researchers took interest in it and examined it more closely.

Scientists then made an astonishing discovery concerning the fossil of the small animal, which is about 7 cm long. “This is the first and only known vampyropod to possess 10 functional appendages”, says Christopher Whalen in a press release, lead author of the study, postdoctoral researcher in paleontology at the AMNH and postdoctoral fellow in the Department of Earth and Planetary Sciences at Yale. soft tissues, which do not fossilize easily. This is surely why these species are so little studied. They are also typically characterized by eight arms and an inner chitinous shell and/or fin supports.

Furthermore, the molecular clock of the lineage suggests that vampyropods appeared there 350 at 328 millions of years. However, the oldest previously known specimen is a fossil dating from around 200 million years. The 10 functional arms and the 328 million years of Syllipsimopodi bideni, thus completely changing the situation.

Dating Syllipsimopodi bideni
La nouvelle étude suggère que le Syllipsimopodi bideni serait âgé de 328 millions d’années. Abréviations des périodes géologiques (couleurs de la Commission internationale de stratigraphie) :  = Cambrien (vert foncé), O = Ordovicien (sarcelle), S = Silurien (bleu clair), D = Dévonien (marron), C = Carbonifère (bleu), P = Permien (rouge orange), TR = Trias (violet), J = Jurassique (cyan), K = Crétacé (vert), PG = Paléogène (orange), N = Néogène (jaune), sans étiquette = Quaternaire (jaune pâle). © K. Whalen.

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The new study suggests that Syllipsimopodi bideni would be million years. Geological period abbreviations: Ꞓ = Cambrian (dark green), O = Ordovician (teal), S = Silurian (light blue), D = Devonian (brown), C = Carboniferous (blue), P = Permian (orange red), TR = Triassic (purple), J = Jurassic (cyan), K = Cretaceous (green), PG = Paleogene (orange), N = Neogene (yellow), unlabeled = Quaternary (pale yellow). © K. Whalen.

Confirmation of a theory

According to the new study by New York researchers, the ten tentacles of Syllipsimopodi bideni were all equipped with suction cups. This makes it the oldest known cephalopod to develop. “The number of arms is one of the defining characteristics separating the lineage of squid and cuttlefish at 10 arms (Decabrachia) of the line of eight-armed octopuses and vampires of the abyss (vampyropods)

”, explains Whalen.

Indeed, previous studies had already hypothesized that the common ancestor of vampyropods had ten arms, because two vestigial appendages are visible on the fossilized specimens, which have eight. Two filaments were therefore eliminated during their evolution. However, all previously discovered fossil vampyropods, whose appendages are visible, had only eight arms. Thus, the fossil of the new species “ is undoubtedly the first confirmation of the idea that all cephalopods had ancestrally ten arms,” says the study, published in the journal Nature Communications.

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The fossil of Syllipsimopodi bideni, at the Royal Ontario Museum. © Christopher Whalen

In addition, two of the cephalopod’s tentacles seem longer compared to the others, and its torpedo-shaped body is similar to that of modern squids. According to the researchers, these longer arms with suction cups allowed the animal to better grasp its prey. It also had a kind of sword as well as terminal fins. “Syllipsimopodi bideni may have filled a niche more similar to extant squids, a mid-level aquatic predator”, says Neil Landman, co-author of the study and curator at the AMNH. According to the expert, the small animal would probably be able to extract small ammonoids from their shells or venture closer to the coast to attack brachiopods, bivalves or other shelled marine animals.

As for the age, characteristics and phylogenetic position of the species, the fossil challenges long-standing assumptions about the origins of the vampyropods. Among these theories, the super-order is descended from a Triassic phragmoteuthid belemnoid (251 at 201,6 million years). The authors then propose a different model for the evolution of coleoids (cephalopods with an internal shell). According to them, the vampyropods were characterized by the loss of the chambered phragmocone and the primordial rostrum, as early as the Mississippian (359,9 to 323,2 million years). However, these features are preserved in the belemnoids and many current decabrachia. In addition, the pair of elongated tentacles, the long sword and the fins, indicate a morphology almost similar to today’s squids.

Source: Nature Communications