Diagnostic characters: Small to medium-sized fishes with elongate, compressed body that tapers
posteriorly. Body without scales or bony plates. Lateral line complete, running along middle of body
and extending nearly to caudal-fin base. A dendritic organ, located along ventral midline of body just
anterior to anal-fin origin and posterior to anus, found in all marine, and some fresh-water species.
Head broad, slightly depressed. Dorsal profile of head from snout tip to dorsal-fin origin straight or arched.
Mouth surrounded with barbels in 4 pairs; 1 pair between widely separated anterior and posterior
nostrils; 1 pair at corner of mouth and 2 pairs on lower jaw. Posterior nostril slit-like, located at base of
nasal barbel; anterior nostril with rounded opening; anterior nostril located either above upper lip margin or
within fleshy lip. Teeth present on jaws, except on upper jaw of some fresh-water species. Palate with
teeth, often molariform; molariform teeth sometimes found in lower jaw. Dorsal and pectoral fins
located just posterior of head, each with a pungent serrated spine at leading edge; fin spines venomous
and capable of producing painful sting; anal fin long and continuous with rounded or pointed
caudal fin; dorsal series of procurrent caudal-fin rays consists of elongate rays which, in marine
species, extend the fin anteriorly to at least vertical line at anal-fin origin, thus forming a second
dorsal fin that is continuous with caudal fin; dorsal adipose fin absent. Colour (in preservative): tan,
brown, or black on sides and dorsum; lighter ventrally; sometimes with light stripes along side of body,
extending onto head.