Penion marwicki is an extinct species of marine snail or whelk, belonging to the true whelk family Austrosiphonidae.

[1][2][3] Penion marwicki is a large, extinct species of Penion siphon whelk.

[2][3] The extinct species Penion exoptatus, Penion clifdenensis, and potentially also Penion marwicki, may belong to the same evolutionary lineage as the extant species Penion sulcatus.

[4] This hypothesis is based on geometric morphometric analysis of shell shape and size for all four taxa, as well as the analysis of morphometric variation exhibited all living species of Penion.

[4] Fossils of Penion marwicki are found in the South Island of New Zealand, and are relatively common at sites in North Otago and South Canterbury.