Ancient fish fossils puzzle scientists, new classification debated

Scientists are pondering the classification of one of the ancient fish species. The two specimens discovered so far do not allow for a precise assessment of what this animal is. However, we may have reached a breakthrough.

A recent review of two fossils of the mysterious ancient fish species Pegasus volans has surprised scientists, indicating the ambiguity of the existing theories about it. The study, published on the bioRxiv platform and although not yet peer-reviewed, points to the uncertainty of this species' position in the phylogenetic tree. This contributes to the debate on the correct classification of this species' representatives.

Pegasus volans, known since the 18th century, were extracted from the rocks of the Bolca Lagertatte formation in northern Italy and dated to about 50 million years ago. Its remains are stored in the Paris Museum of Natural History and the Civic Museum of Natural History in Italy.

This animal is depicted as having an unusual body structure, long fins, and a prominent skull. Because of this, it is difficult to classify it definitively. An additional complication is that both specimens we have are incomplete, making it difficult to determine, among other things, the stage of the animal's development.

In both discovered fossils, the rear part of the fish's body is missing. Discovering a new fossil could significantly facilitate the classification of the animal and determine whether it is a juvenile or an adult.

In the past, scientists have suggested various taxonomic assignments for Pegasus volans, including the hypothesis that it may be a larval form of modern fish of the genus Pegasus. However, as palaeontologist Donald Davesne from MNHN explains, such a comparison does not seem accurate. Another theory was assigning it to Lampriformes, but the new study also questions this classification.

Current considerations indicate that Pegasus volans might be related to Acanthomorpha – a group of fish among which we find fish with spiny fin rays. Davesne and Giorgio Carnevale propose a new generic name that would better reflect the nature of the find. This name, inspired by a deceased musician, will be revealed only at the official publication of the research.

Davesne summarised that he doesn't know what it is not, but it is not clear what it might be.

The discovery of a complete specimen of Pegasus volans could significantly contribute to solving the mystery of its taxonomic classification. In the meantime, scientists emphasise the need for further research to separate the true theories from the erroneous ones.