Ostéologie et relations de <i>Ligulella</i> (Halecostomi, Ligulelliformes nov. ord.), poisson du Jurassique moyen de Kisangani (Formation de Stanleyville) en République Démocratique du Congo
The osteology of Ligulella, a very small halecostome fish from the Middle Jurassic of Kisangani (Stanleyville Formation) in the Democratic Republic of Congo, is studied in detail on the basis of more than 100 specimens. It is shown that the genus is monospecific and that Ligulella fourmarieri is a junior synonym of Ligulella sluysi. The dermic bones of the skull roof are covered by a thin and smooth layer of ganoin. The lateral borders of the skull roof are ornamented with a fringe of large bony spines. A small toothed laterodermethmoid is located medially at the symphysis of the upper jaw and rejects laterally the premaxillae. The quadrate is devoid of a bony quadratic process. Both quadrate and symplectic articulate with the lower jaw. Based on its characters Ligulella has to be positioned in the neopterygian phylogenetic tree between the Pachycormiformes and the "Pholidophoriformes", allowing the creation of a new and peculiar ordinal status for it, the Ligulelliformes nov. ord
