Penion proavitus fossils are the earliest known specimens of Penion siphon whelks.[3][4] The species was medium-to-large in size.[2][5]
It is possible that fossils of Penion proavitus represent a stem lineage that was the common ancestor of Penion, Kelletia and Antarctoneptunea, instead of a species of Penion itself.[4]
^ abcFinlay, Harold J.; Marwick, John (1937). "The Wangaloan and Associated Molluscan Faunas of Kaitangata-Green Island Subdivision". New Zealand Geological Survey Paleontological Bulletin. 15.
^ abcBeu, Alan G.; Maxwell, P.A. (1990). Cenozoic Mollusca of New Zealand. New Zealand Geological Survey Bulletin. Vol. 58. Lower Hutt, New Zealand: New Zealand Department of Scientific and Industrial Research. ISSN0114-2283.
^ abcVaux, Felix; Hills, Simon F.K.; Marshall, Bruce A.; Trewick, Steven A.; Morgan-Richards, Mary (2017). "A phylogeny of Southern Hemisphere whelks (Gastropoda: Buccinulidae) and concordance with the fossil record". Molecular Phylogenetics and Evolution. 114 (2017): 367–381. doi:10.1016/j.ympev.2017.06.018. PMID28669812.