The tubemouth (Siphonognathus argyrophanes) is a species of ray-finned fish, a weed whiting from the family Odacidae.

The tubemouth has a highly elongated head and body and has a fleshy barbel which protrudes from the end of the upper lip.

[4] The tubemouth occurs in sheltered areas where there is a dense growth of Posidonia sea grass,[3] no deeper than 40 metres (130 ft).

[1] The tubemouth closely resembles the cornetfishes and trumpetfishes of the order Syngnathiformes in body shape and form, this is an example of convergent evolution.

The extremely slender body and highly elongated snout, are apparent in other members of the genus Siphonognathus, these features, in combination with the lack of pelvic fins, possession of a barbel on the upper lip and extraordinarily high counts of vertebrae, fin rays and lateral-line scales make it very different from its congeners.