Belongs within: Buccinoidea.
Contains: Penion.
Southern siphons
Published 29 January 2026
We’re used to thinking of the tropics as the centre of biodiversity. Most lineages of plants and animals seem to get more diverse the closer one gets to the equator. But this stands by way of a guideline, not a rule, and there are some noteworthy exceptions. One such example is the Buccinoidea, the whelks, a diverse assemblage of mostly predatory gastropods that find their centres of speciation towards the cooler waters of the poles. As with other subgroups of the neogastropods, buccinoid classification has been historically unsteady, and a recent study of their phylogeny by Kantor et al. (2022) lead to the recognition or resurrection of a number of families. Among these were the Austrosiphonidae.
The name Austrosiphonidae was first established in 1938 but had seen little recognition until Kantor et al.’s revision. As recognised by these authors, the austrosiphonids are a small family, encompassing just four genera: Antarctoneptunea, Kelletia, Penion and Serratifusus. They are medium-sized to large whelks, with the shells of the smallest about 3.5 centimetres in length and those of the largest up to 22 cm. The front of the shell is drawn out into a more or less elongate siphonal canal. The shell is often distinctly sculpted, with a spiral sculpture of multiple cords and usually axial ribs, knobs or spines on the shoulder of the whorls. The opening is closed by a leaf-shaped operculum.
The radula is a fairly typical one for buccinoids, with a subrectangular central tooth bearing usually three cusps, and large lateral teeth bearing three to seven (most often three) cusps. The outermost cusp of the lateral teeth is larger than the rest, curved into a wicked hook. Like other buccinoids, the austrosiphonids are presumably predatory, taking down other marine animals such as worms or echinoderms, though they may also not be above scavenging.
As the genus name Antarctoneptunea suggests, austrosiphonids are more diverse in the cooler waters of the Southern Hemisphere, around Antarctica and Australasia. They are found subtidally, with some species reaching bathyal depths. Most are direct developers, though species of Kelletia have planktotrophic larvae. It may be that this last feature is connected to their distinctive distribution. Kelletia is the only austrosiphonid genus found in the Northern Hemisphere, with species off the coasts of Japan and California. At some point, their ancestors successfully crossed the forbidding waters of the tropics, settling down when they reached the safety of cooler climes on the other side.
Systematics of Austrosiphonidae
<==AustrosiphonidaeKF22
|--Serratifusus Darragh 1969KF22, RD75
| |--*S. crasspedotus (Tate 1888) [=Fusus crasspedotus]RD75
| `--S. lineatus Harasewych 1991KF22
`--+--+--Kelletia Bayle 1884KM23, O27
| | |--*K. kelletii (Forbes 1852) [=Fusus kelletii]KF22
| | `--K. lischkei Kuroda 1938KF22
| `--PenionKM23
`--Antarctoneptunea Dell 1972KF22
|--*A. aurora (Hedley 1916) [=Fusitriton aurora]KF22
`--A. benthicola (Dell 1956) [=Penion benthicola]KF22
*Type species of generic name indicated
References
[KF22] Kantor, Y. I., A. E. Fedosov, A. R. Kosyan, N. Puillandre, P. A. Sorokin, Y. Kano, R. Clark & P. Bouchet. 2022. Molecular phylogeny and revised classification of the Buccinoidea (Neogastropoda). Zoological Journal of the Linnean Society 194 (3): 789–857.
[KM23] Kantor, Y., T. Molodtsova, S. Zvonareva & A. Fedosov. 2023. Taxonomy of Antarctic Buccinoidea (Gastropoda: Neogastropoda) revisited based on molecular data. Invertebrate Systematics 37 (4): 271–299.
[O27] Oldroyd, I. S. 1927. The Marine Shells of the West Coast of North America vol. 2 pt 1. Stanford University Press: Stanford University (California).
[RD75] Radwin, G. E., & A. D’Attilio. 1975. A catalogue of muricacean generic taxa. Transactions of the San Diego Society of Natural History 17 (20): 279–292.