Eocene-Epoch Stingray Had Unique Body Plan

A new species of prehistoric stingray with an exceptional anatomy, which greatly differs from living species, has been identified from fossils found in Italy.

Lessiniabatis aenigmatica from the Eocene of Bolca Lagerstätte. Scale bars – 10 cm. Image credit: Marrama et al, doi: 10.1038/s41598-019-50544-y.

Lessiniabatis aenigmatica from the Eocene of Bolca Lagerstätte. Scale bars – 10 cm. Image credit: Marrama et al, doi: 10.1038/s41598-019-50544-y.

“Stingrays (order Myliobatiformes) are a very diverse group of cartilaginous fishes comprising more than 360 extant species arranged in 11 families,” explained Dr. Giuseppe Marrama, a paleontologist with the Institute of Paleontology at the University of Vienna, and colleagues.

“They are known for their venomous and serrated tail stings, which they use against other predatory fish, and occasionally against humans. They have a rounded or wing-like pectoral disc and a long, whip-like tail that carries one or more serrated and venomous stings.”

“Fossil remains of stingrays are very common, especially their isolated teeth. Complete skeletons, however, exist only from a few extinct species coming from particular fossil sites.”

“Among these, the rich fossil site near Bolca in northeastern Italy is one of the best known.”

Silhouettes of selected living and fossil species as representatives for the modern stingray families and holomorphic fossil species: (a) Hexatrygon bickelli, (b) Dasyatis marmorata, (c) Potamotrygon tigrina, (d) Urobatis halleri, (e) Plesiobatis daviesi, (f) Urolophus kapalensis, (g) Lessiniabatis aenigmatica, (h) Asterotrygon maloneyi, (i) Heliobatis radians, (j) Gymnura altavela, (k) Promyliobatis gazolai, (l) Myliobatis hamlyni, (m) Aetobatus laticeps, (n) Rhinoptera bonasus, (o) Mobula mobular. Image credit: Marrama et al, doi: 10.1038/s41598-019-50544-y.

Silhouettes of selected living and fossil species as representatives for the modern stingray families and holomorphic fossil species: (a) Hexatrygon bickelli, (b) Dasyatis marmorata, (c) Potamotrygon tigrina, (d) Urobatis halleri, (e) Plesiobatis daviesi, (f) Urolophus kapalensis, (g) Lessiniabatis aenigmatica, (h) Asterotrygon maloneyi, (i) Heliobatis radians, (j) Gymnura altavela, (k) Promyliobatis gazolai, (l) Myliobatis hamlyni, (m) Aetobatus laticeps, (n) Rhinoptera bonasus, (o) Mobula mobular. Image credit: Marrama et al, doi: 10.1038/s41598-019-50544-y.

Dr. Marrama and co-authors found three nearly complete specimens of a previously unknown stingray species at the Bolca site.

Named Lessiniabatis aenigmatica, the creature lived some 50 million years ago (Eocene epoch) in the waters of the western Tethys Ocean.

It had a flattened body and a pectoral disc ovoid in shape. What is striking is the absence of sting and the extremely short tail, which was not long as in the other stingrays and didn’t protrude posteriorly to the disc.

This unique body plan is unknown in other extinct or living species of stingrays.

“More than 70% of the organisms, such as dinosaurs, marine reptiles, several mammal groups, numerous birds, fish and invertebrates, disappeared during the fifth largest extinction event in the Earth’s history that occurred about 66 million years ago at the end of the Cretaceous period,” the researchers said.

“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 fishes (sharks and rays), which reoccupied the ecological niches left vacant by the extinction’s victims.”

“From this perspective, the emergence of a new body plan in a 50-million-year-old stingray such as Lessiniabatis aenigmatica is particularly intriguing when viewed in the context of simultaneous, extensive diversification and emergence of new anatomical features within several fish groups, during the recovery of the life after the end-Cretaceous extinction event,” Dr. Marrama said.

A paper on the discovery is published in the journal Scientific Reports.

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Giuseppe Marramà et al. 2019. A bizarre Eocene dasyatoid batomorph (Elasmobranchii, Myliobatiformes) from the Bolca Lagerstätte (Italy) reveals a new, extinct body plan for stingrays. Scientific Reports 9, article number: 14087; doi: 10.1038/s41598-019-50544-y

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