Popular Science: Vampire squid tales, or how they came to their deep-water habitat
The fossil has complemented our knowledge of vampire squids. These deep-water animals are rarely represented in the paleontological record, and so every sample from the past matters. The discovery is so significant that it was even noticed by the leading Czech news platforms some time ago. The holotype (a specimen according to which a particular species is described) of an animal was considered destroyed or lost.
The oldest ancestors of today’s vampire squids (cephalopods of the order Loligosepiina) probably appear in the paleontological record at the very end of the Triassic period. With their internal shell (gladius), they are practically identical to vampire squids. Today, these animals inhabit deep ocean waters with a lack of oxygen (OMZs, oxygen minimum zones) and feed mainly on marine snow (detritus), which drifts into the lower layers of the ocean from surface waters. They have eight arms connected by skin webbing, luminescent organs and large globular eyes. Today, only one species is known to live, Vampyroteuthis infernalis.
The journey of vampires to the places where they survived till today has been affected by anoxic (the absence of oxygen in water and other environments) events (OAEs; oceanic anoxic events) in the Earth’s geological past. However, based on the unique paleontological record of this group, the scientists were able to reconstruct the gradual migration of vampire squids to depths of as low as one kilometer.
The finds of these cephalopods come mainly from localities with exceptional preservation of fossils (also known as Lagertstätten). Finds of the ancestors of today’s vampire squids from the rocks of the northwestern part of the European shelf come from the Lower Jurassic period (Toarcian stage). The anoxic event of this time (TOAE) was characterized by rising ocean temperatures, limited ventilation, and increased supply of land-based material and water, resulting in significant stratification of the world’s ocean waters. However, it is difficult to judge why the vampire squid ancestors inhabited this hypoxic habitat with minimal predation and competitive pressures, which was characterized by short-term supplies of oxygenated water.
The findings of these animals come from the Middle Jurassic (Callovian) from a site in La Voulte-sur-Rhône in France. Specific soft-body preservation from reduction conditions with a lack of oxygen (very low carbon isotope ratios) and a minimum of bioturbations (traces of drilling organisms in the ocean floor) indicate hypoxic to anoxic conditions in the sea at the time. During this period, vampire squids still stayed on the shelf at depths of about 200 meters. However, more significant changes in the paleoenvironment did not happen until the Upper Cretaceous.
During the Cretaceous period, several significant anoxic events occurred (OAEI-OAEIII). The last Mesozoic finds of the ancestors of today’s vampire squids (still on shelves only) also come from rocks of the Aptian stage (during OAEI). During other anoxic events, they no longer appeared in the paleontological record from the same depths. We can therefore conclude that at the turn of the Lower / Upper Cretaceous, their habitats shifted to greater depths. Within OAEII and OAEIII, we no longer encounter them in the rock from then shelves.
The specimen described in the article by Košťák comes from the Oligocene period. There is a hiatus of 90 million years in the fossil record between it and the Mesozoic representatives of the vampire squids’ ancestors. Necroteuthis hungarica, as the animal was named, lived at depths of over 400 meters in hypoxic/anoxic to euxinic (anoxia + high hydrogen sulfide) conditions. The migration to greater depths could be caused both by the predation pressure of other animals and by the presence of specific conditions, such as the level of oxygen at these depths. The deep-water way of life then probably saved vampire squids from massive extinction at the end of the Cretaceous period. The paper confirms that vampires have been living in these conditions for at least 30 million years.
Vampires are an example of an animal with which every fossil finding is important for understanding their past. The re-appearing of organisms in the fossil record is called the “Lazarus taxon” and, apart from vampire squids, is known, for example, in lampreys, hagfish and coelacanths.