Abstract
Coelacanths form a clade of sarcopterygian fish represented today by a single genus, Latimeria. The fossil record of the group, which dates back to the Early Devonian, is sparse. In Switzerland, only Triassic sites in the east and southeast of the country have yielded fossils of coelacanths. Here, we describe and study the very first coelacanth of the Jurassic period (Toarcian stage) from Switzerland. The unique specimen, represented by a sub-complete individual, possesses morphological characteristics allowing assignment to the genus Libys (e.g., sensory canals opening through a large groove crossed by pillars), a marine coelacanth previously known only in the Late Jurassic of Germany. Morphological characters are different enough from the type species, Libys polypterus, to erect a new species of Libys named Libys callolepis sp. nov. The presence of Libys callolepis sp. nov. in Lower Jurassic beds extends the stratigraphic range of the genus Libys by about 34 million years, but without increasing considerably its geographic distribution. Belonging to the modern family Latimeriidae, the occurrence of Libys callolepis sp. nov. heralds a long period, up to the present day, of coelacanth genera with very long stratigraphic range and reduced morphological disparity, which have earned them the nickname of 'living fossils'.