nounhistorical, rare Zoology
A (former) division of bony fishes comprising those with pelvic fins located on the belly, between the pectoral and anal fins; fishes of this division.
Although zoologists no longer regard Abdominales as a taxonomic group, the location of the pelvic fins is still a characteristic used in the description of fishes, the abdominal location being typical of relatively primitive teleosts.
Late 18th century; earliest use found in Encyclopaedia Britannica. From scientific Latin Abdominales, name of a division of fishes (LinnaeusSystema Naturae (ed. 10, 1758) I. 330), use as noun of masculine plural of post-classical Latin abdominalis.