Sciaenidae

The morphology of the sound producing mechanism is examined in four
species of Equetus, an undescribed species of Pareques, Odontoscion
dentex, and Umbrina coroides. The mechanism involves a pair of
extrinsic sonic muscles which originates on the abdominal body walls and
extends upwards to insert on a tendon dorsal to the airbladder. A
portion of the airbladder is thus encircled by the sonic muscles and
tendon. The fundamental arrangement of the sonic muscles is the same in
all the species examined with variations in size, shape, and position of
the muscles occurring among species. The sonic muscles are present in
males only. A previously undescribed thin-walled area exists in the
region demarcated by the sonic muscles on the male airbladder. The
basal processes of the first four vertebrae are described in males. No
vertebral differences exist between male and female specimens.