New pycnodont fish genus (Neopterygii : Pycnodontiformes) from the cenomanian (upper cretaceous) of mount Lebanon

摘要

A new taxon of pycnodont fishes, Hensodon, is described on the basis of a well-preserved and articulated skeleton front the Cenomanian limestones of Hakel, Lebanon. A single species, Hensodon spinosus (Hennig, 1907), is assigned to the new genus. Hensodon is placed within Coccodontidae and is sister to Trewavasia. Features of Hensodon are: three massive, paired parietal and postparietal spines: a well-developed dorsal prominence rising to a high and distinct spinose apex, with the leading edge being straight and covered by a series of nuchal plates; two styliform dentalosplenial teeth and knoblike molariform prearticular and vomerine teeth: styliform branchial teeth; peltate squamation with only eight scale rows: and pelvic and anal fins preceded by strong and accentuated spines. The similar pycnodont Trewavasia differs in the presence of a single paired parietal spine, dorsal prominence without apical spines, loricate squamation pattern, scales with horizontal keels ending in a posterior spine, a dermal plate on the anterior ventral body part, no ventral apex, and a considerably higher number of hypurals. The phylogeny of pycnodonts is discussed and the paleobiogeographic patterns of Lebanese pycnodonts are reviewed.