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"An Experiment of Nature" – Fossil fish gives new insights into evolution after a mass extinction

  Fossils of Lessiniabatis Aenigmatica

One of the three fossils of Lessiniabatis Aenigmatica (MNHN F.Bol.566) obtained from the famous fossil site of Monte Bolca (Italy) as part and counterpart. The copy is in the Museum National d & # 39; Histoire Naturelle of Paris. Photo credits: © Giuseppe Marramà

An international team of researchers headed by Giuseppe Marramà from 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 find provides new insights into the evolution of these animals and sheds light on the restoration of marine ecosystems after the mass extinction 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 poisonous and serrated tail-stings that they use against other predatory fish and occasionally against humans. These rays have a rounded or wing-like breast disc and a long, whip-like tail that carries one or more jagged and venomous stings. The stingrays include the largest rays in the world, such as the gigantic mantas, which can reach a span of up to seven meters and a weight of about three tons.

  Live Stingrays

Two live stingrays: a) Taeniura Lymma; b) Neotrygon sp. The specimens are in the collection of the Institute of Paleontology of the University of Vienna. Photo credits: © Giuseppe Marramà

Fossil remains of stingrays are very common, especially their isolated teeth. Complete skeletons exist, however, only a few extinct species that come from specific fossil sites. Among these, the Monte Bolca in northeastern Italy is one of the best known. To date, more than 230 fish species have been discovered that document a tropical marine environment associated with coral reefs dating back to the Eocene about 50 million years ago.

This new fossil stingray has a flattened body and egg-shaped breast disc. Striking is the lack of spines and the extremely short tail, which is not as long as the other stingrays and does not protrude backwards from the intervertebral disc. This body plan is not known in any other fossil or live stingray. Since this animal is unique and peculiar, the researchers called the new stingray Lessiniabatis aenigmatica, which means "bizarre ray from Lessinia" (the Italian area in which Bolca is located).

More than 70 percent of organisms, such as dinosaurs, marine reptiles, several mammal groups, numerous birds, fish and invertebrates, disappeared during the fifth largest extinction event in the history of Earth, approximately 66 million years ago at the end of the Cretaceous. In the marine environment, the aftermath of this event is characterized by the emergence and diversification of new species and groups of bony and cartilaginous fish (sharks and rays) that reoccupied the ecological niches that the victims of extinction had. The new species sometimes experimented with new body plans and new ecological strategies.

"From this perspective, the emergence of a new body plan on a 50-million-year-old stingray such as Lessiniabatis aenigmatica in context is particularly intriguing in the simultaneous, extensive diversification and emergence of new anatomical features within several fish groups during the restoration of life after the extinction of the Cretaceous "Explains Giuseppe Marramà.

Note: "A bizarre Eocene dasyatoides atomorph (Elasmobranchii, Myliobatiformes) from the Bolca deposit (Italy) reveals a new, extinct stingrays body plan" by Giuseppe Marrama, Giorgio Carnevale, Gavin JP Naylor, Luca Giusberti and Jürgen Kriwet, 1 October 2019, Scientific Reports ] DOI: 10.1038 / s41598-019-50544-y

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