The morphology and histology of the scales of Aspidorhynchidae (Actinopterygii, Halecostomi).

The scales of the three genera of aspidorhynchids (Aspidorhynchus, Belonost omus, and Vinctifer) are studied to bring out some characters useful to und erstand the systematic position of aspidorhinchids within the neopterygians . The scales of the nine species studied are of lepidosteoid type with a ga noine layer overlaying a basal plate made of lamellar bone with canalicules of Williamson. Some species of Aspidorhynchus are devoid of ganoin, wherea s others show only a thin ganoine layer. None of the characters found in th e scales of aspidorhynchids can be considered as a familial synapomorphy ab le to place the clade within the teleosts, a situation that does not imply the exclusion of this family from this major group.