A new extinct species of coelacanth discovered thanks to the ESRF

Fossilisation is a process that allows the preservation of plants and animals in rocks for
hundreds of millions of years. During this period, geological upheavals often deteriorate
fossils and paleontologists put great deal of effort and imagination into reconstructing
organisms as they were when they were alive.

A team of paleontologists from the MHNG and UNIGE, in collaboration with researchers from the Senckenberg Research Institute, Natural History Museum in Frankfurt am Main (Germany) and the ESRF, have just published a paper that shows the discovery of some 240-million-year-old coelacanth fossils, which show extremely detailed characteristics of of their preserved skeleton that had never been observed before.

Coelacanths are fish of which there are only two current species and which, with a few
exceptions, evolved slowly over more than 400 million years. The fossils studied by
the international team were discovered in clay nodules from the Middle Triassic period in Lorraine (France), near Saverne. The specimens, about fifteen centimetres long, are
preserved in three dimensions.

Some specimens were analysed at the ESRF in Grenoble. After hundreds of hours of work consisting of virtually individualising the bones of the skeleton by computer, the team obtained virtual 3D models of the fossils that can be easily studied. 

The results enabled the team to reconstruct the skeleton of these fish with a level of detail never obtained before for this type of fossil.

A 3D rendering of the new species using X-ray tomography at the ESRF. Credits: L. Manuelli.

This is a new species named Graulia branchiodonta, named after Graoully, a mythical dragon from Lorraine folklore and in reference to the large teeth that these fish have on their gills. The specimens are juvenile individuals characterised, in particular, by highly developed sensory canals. It was probably a much more active species than Latimeria, the existant coelacanths whose behaviour is very indolent. Graulia also had a large gas bladder which could have a respiratory or auditory function or could participate in buoyancy.

The researchers at the Natural History Museum of Geneva are continuing the study of Triassic
coelacanths, a few million years old after the greatest mass extinction of the last 500 million
years, by describing new fossils discovered in various places around the world. They are
interested in their astonishing morphological characteristics, but also genetic ones based on
the comparison of the genomes of current vertebrates.

Reference: Manuelli, L. et al, The most detailed anatomical reconstruction of a Mesozoic coelacanth, PLOSOne, November 6, 2024, https://doi.org/10.1371/journal.pone.0312026