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'An experiment of nature' – fossil fish gives new insights into the evolution after a mass extinction

  Fossils of Lessiniabatis Aenigmatica

One of the three fossils of Lessiniabatis aenigmatica (MNHN F.Bol.566) from the famous fossil site Monte Bolca (Italy), which was preserved as part and equivalent. The example is housed in the National Museum of Natural History in Paris. Credit: © Giuseppe Marramà

An international research team led by Giuseppe Marramà of the Institute of Paleontology at the University of Vienna discovered a new and well-preserved fossil stingray with an exceptional anatomy that is very different from living species. The findings provide new insights into the evolution of these animals and illustrate the recovery of marine ecosystems after the mass extinction occurred 66 million years ago. The study was recently published in the journal Scientific Reports .

Stingrays (Myliobatiformes) are a very diverse group of cartilaginous fish known for their toxic and toothed tail sticks, which they use against other predators, and sometimes against humans. These rays have a rounded or wing-like pectoral disc and a long, whip-like tail bearing one or more grooved and poisonous sticks. Stingrays include the world's largest rays such as the giant manta rays, which can reach a "wingspan" of up to seven meters and a weight of about three tons.

  Living Stingrays

Two living stingrays: a) Taeniura sap; b) Neotrygon sp. The samples are in the collection from the Institute of Paleontology at Vienna University. Credit: © Giuseppe Marramà

Fossil remains of stingrays are very common, especially their isolated teeth. However, complete skeletons exist only from a few extinct species that originate from certain fossil areas. Among these, Monte Bolca in northeastern Italy is one of the most famous. To date, more than 230 species of fish have been discovered that document a tropical marine coastal environment associated with coral reefs dating back to approximately 50 million years ago during the Eocene period.

This new fossil stingray has a planned body and a pectoral disk that is ovoid in shape. What is striking is the absence of the stick and the extremely short tail, which is not long as in the other sticks, and which does not protrude backwards on the disc. This body plan is not known in any other fossil or living stingray. Because this animal is unique and strange, the researchers chose the new stingray Lessiniabatis aenigmatica, which means "bizarre ray from Lessinia" (the Italian area where Bolca is located).

More than 70 percent of organisms, such as dinosaurs, marine reptiles, multiple mammal groups, many birds, fish, and invertebrates, disappeared during the fifth largest extinction event in earth's history, occurring about 66 million years ago at the end of the Cretaceous. In marine environments, the time after this event is characterized by the emergence and diversification of new species and entire groups of bony and cartilaginous fish (sharks and rays), which reopened the ecological niches left vacant by the extinction victims. The new species sometimes experimented with new body plans and new ecological strategies.

"From this perspective, the emergence of a new body plan in a 50 million year old stingray like Lessiniabatis aenigmatica is particularly exciting when viewed in the context of simultaneous, extensive diversification and emergence of new anatomical functions in several fish groups, during the recovery of life. after the final Cretaceous extinction event, "says Giuseppe Marramà.

Reference:" A bizarre Eocene dasyatoid batomorph (Elasmobranchii, Myliobatiformes)) from Bolca Lagerstätte (Italy) reveals a new, extinct body plan for stickers ", by Guseppe Mario Luca Giusberti, Gavin JP Naylor and Jürgen Kriwet, October 1, 2019, Scientific Reports .
DOI: 10.1038 / s41598-019-50544-y

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