Rhamphocottidae sculpins have a single pharyngobranchial bone. In the pectoral fins several of the lower pectoral rays are separated from the upper lobe and are free of the fin membrane. There are fin stays in the dorsal and anal fin. The tail has all parts of the hypural and parhypural fused into a single complex structure. The smallest species is the grunt sculpin with a maximum published total length of while the largest is Ereunias grallator which reaches a maximum published total length of.