A new species of Gladiopycnodus (Coccodontoidea,Pycnodontomorpha) from the Cretaceous of Lebanon provides new insights about the morphological diversification of pycnodont fishes through time |
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| Institution: | 1. Dipartimento di Scienze della Terra, Università degli Studi Torino, Via Valperga Caluso, 35 I-1025 Torino, Italy;2. Soprintendenza per i Beni Archeologici del Friuli Venezia Giulia, Nucleo Operativo di Udine, Via Zanon, 22 I-33100 Udine, Italy;1. Facultad de Ciencias, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, Coyoacán, 04510 México, D.F., Mexico;2. Posgrado en Ciencias de la Tierra, Instituto de Geología, Universidad Nacional, Autónoma de México, Circuito Exterior, Ciudad Universitaria, Coyoacán, 04510 México, D.F., Mexico;3. Earth and Planetary Sciences, McGill University, 3450 University Street, Montreal, Quebec H3A OE8, Canada;4. Posgrado en Ciencias Biológicas, Instituto de Geología, Universidad Nacional, Autónoma de México, Circuito Exterior, Ciudad Universitaria, Coyoacán, 04510 México, D.F., Mexico;5. Estación Regional del Noroeste, Instituto de Geología, Universidad Nacional Autónoma de México, Apartado Postal 1039, 83000 Hermosillo, Sonora, Mexico;1. Museo de Paleontología “Eliseo Palacios Aguilera”, Secretaría de Medio Ambiente e Historia Natural., Calzada de Los Hombres Ilustres s/n., Tuxtla Gutiérrez, Chiapas, Mexico;2. Instituto de Geología, Universidad Nacional Autónoma de México; Circuito de la Investigación S/N, Ciudad Universitaria, Coyoacán, D.F., 04510, Mexico;1. Univ Rennes, CNRS, Géosciences Rennes, UMR CNRS 6118, Campus de Beaulieu, 263, avenue du Général Leclerc, F-35000 Rennes, France;2. 4, rue Saint-Just, F-17000 La Rochelle, France;3. Musée d’Angoulême, 1, rue Friedland, F-16000 Angoulême, France;4. 23A, rue des Barraudes, La Cotinière, F-17310 Saint-Pierre-d’Oléron, France |
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| Abstract: | The Coccondontoidea is a distinctive superfamily of pycnodont fishes characterized by a series of derived characters, including thick and well-ossified cranial bones supporting horns and spines and a hypertrophied pectoral girdle sutured to the skull forming a sort of cephalo-torax. A new distinctive coccodontoid species, Gladiopycnodus byrnei n. sp., is described from the Cenomanian locality of Hjoûla, Lebanon. This new species exhibits a unique combination of features that clearly support its inclusion within the coccodontoid family Gladiopycnodontidae, including an extremely elongate snout forming a sword-shaped rostrum, thick dermal bones ornamented with rounded tubercles, large supracleithrum and cleithrum extensively sutured to the skull, and irregularly imbricated scales covering the entire body. The new taxon differs from type species G. karami by having different meristic counts and body proportions, dermal bones strongly ornamentated, skull roof with partially fused bones, scales ornamented with small tubercles, and rounded scales covering the caudal peduncle absent. The presence of pectoral fins in our exquisitely well-preserved specimen allowed us to redefine the morphology of the genus Gladiopycnodus, also modifying the diagnosis of the family. In order to interpret the patterns of morphospace occupation and quantify the morphological diversification of pycnodonts through time, the geometric morphometric approach was used. The morphospace analysis revealed that a significant increase in morphological disparity of pycnodonts during the Late Cretaceous was related, at least in part, to the appearance of the representatives of the superfamily Coccodontoidea. The rapid evolutionary radiation of these well-armored pycnodonts was interpreted as an adaptive solution in response to the large predatory-prey escalation in the context of the Mesozoic Marine Revolution. |
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| Keywords: | Cenomanian Cretaceous Hjoûla in Lebanon Morphospace analysis |
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