GUILDAYICHTHYIFORMES, Lund, 2000

Lund, Richard, 2000, The new Actinopterygian order Guildayichthyiformes from the Lower Carboniferous of Montana (USA), Geodiversitas 22 (2), pp. 171-206 : 173

Superorder CLADISTIA Cope, 1871 Order GUILDAYICHTHYIFORMES n. ord.

DIAGNOSIS. — Paired premaxillae not sutured in midline, maxilla does not extend posterior to midorbital level. Small rostral, paired lateral postrostrals followed by a large median second postrostral. Supraoccipital prominent in skull roof. Two to three rows of paired bones, including supraorbitals, over orbits. Three bones in anteroposterior otic series. Infraorbital series of six to ten bones lacking a specialized posterodorsal infraorbital or “postorbital”. Suborbitals numerous, variable, extending under orbit. Narrow dorsal and ventral preoperculars. Interopercular rays or interopercular bones present, that may carry a branch of the preopercular lateral line canal. Single large opercular bone ventral to two to for smaller postspiraculars; branchiostegal rays few, not extending forward under mandible. Braincase ossified as several bones; parasphenoid extends entire length of braincase. Presupracleithrum large. Body laterally compressed, discoidal; squamation complete, deepened peg-andsocket scales on anterior flank. Caudal hemiheterocercal; fin rays well spaced.