Article révisé par les pairs
Résumé : The cranial osteology of Syntegmodus altus Loomis, 1900, from the Niobrara Formation (Coniacian to Senonian) of Kansas, is studied. This fish belongs to the order Tselfatiiformes. In opposition to a generally admitted opinion, Syntegmodus is not a synonym of Bananogmius but represents a valid genus, characterized by a narrow and very high lateral ethmoid, a parasphenoid with a very developed mid-dorsal wing, a sphenotic hidden by the frontal and the pterotic in dorsal view, and a skull roof where the parietal is anteriorly bordered by the frontal and laterally by both the frontal and the pterotic. Within the Tselfatiiformes, Syntegmodus is more particularly related to Bananogmius and Niobrara, two primitive Plethodidae. The parietal of Bananogmius is anteriorly bordered by the frontal and laterally by the pterotic. This relation between these three bones is the general one within the Tselfatiiformes with a more or less flat skull roof. In Niobrara the parietal is anteriorly and laterally bordered by the frontal while the pterotic is rejected posterior to the parietal. By its skull roof architecture, Syntegmodus is intermediate between these two genera.