The Pycnodonts are an extinct group of Ray-finned Fish known from the Triassic to the Eocene. They are thought to have been more closely related to the Teleosts (the most abundant and diverse group of Fish today, characterized by an unfolding jaw that creates a vacuum as the Fish opens its mouth, sucking in food) and Holosts (Birchirs and Gars) than to the Acipenceriforms (Sturgeons and Paddlefish). The earlier forms of Pycnodonts were flattened and disk-shaped in profile, though from the Late Cretaceous onwards families such as the Coccodontidae, Gebrayelichthyidae, Gladiopycnodontidae and Trewavasiidae produced members with a more diverse range of shapes. Pycnodonts appear to have been restricted to warm, shallow shelf seas, and may have become extinct due to cooling climates in the later Cainozoic, or possibly because of competition with the more successful Teleosts.
In a paper published in the journal Cretaceous Research in June 2016, Giuseppe Marramà and Boris Villier of the Dipartimento di Scienze della Terra at the Universit a degli Studi Torino, Fabio Dalla Vecchia of the Soprintendenza per i Beni Archeologici del Friuli Venezia Giulia, and Giorgio Carnevale, also of the Dipartimento di Scienze della Terra at the Universit a degli Studi Torino, describe a new species of Pycnodont Fish from the Late Cretaceous Hjoûla Lagarstätte of Lebanon.
The new species is placed in the genus Gladiopycnodus, which previously contained a single species, also from the Late Cretaceous of Lebanon, and given the specific name byrnei, in honour of the American musician and composer David Byrne. The species is described from a single articulated and almost complete specimen from the Sannine Limestone at Hjoûla, dated to about 94 million years ago. The specimen is 50.8 mm in length, and is elongate, with a body depth only about a quarter of its length. Gladiopycnodus byrnei has an elongate snout and a sword-shaped anal plate which extends whell beyond the caudal fin (tail), and is covered with stronly overlapping scales.
Gladiopycnodus byrnei, from the Cenomanian of Hjoûla, Lebanon. (A) Specimen; (B) Interpretative reconstruction. Scale bar is 5 mm. Marramà et al. (2016).
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