Chamaesipho grebneffi explained

Chamaesipho grebneffi is the first extinct member of the Notochthamalinae to be described, and the oldest chthamaloid barnacle known. This species is a fully derived Chamaesipho, and indicates a considerable antiquity for Chthamaloidea.

Three extinct species of Chthamalus from the middle Miocene of the faluns of Touraine, France were described in 2008 by Carriol.^[1] the New Zealand species is Oligocene, and considerably older.

Discussion

Like the three living species of Chamaesipho, the shell of C. grebneffi begins with 6 plates, fusing completely at about 2 mm diameter. Freegrown specimens show a stellate basal outline. The scutum is highly distinctive in tergal margin equal in length to basal margin. In all other Chamaesipho, tergal margin is much shorter than basal. The tergum is not definitely identified.

Chamaesipho grebneffi is interpreted, from wear patterns on the shell, to have occupied high littoral positions on shore. Entire assemblage described by Buckeridge indicates shallow agitated waters of several habitat zones.

Nomenclature

• Chamaesipho brunnea . Buckeridge, 1983b: 80^[2] (citation of lower Miocene shells without opercular plates).
• Chamaesipho grebneffi, 2014: 7^[3] (original description).
• Type locality: late Oligocene (near Duntroonian/Waitakian stage boundary), Chatton Formation, Cosy Dell farm, Southland, New Zealand. Known definitely only from this locality.

Notes and References

1. Carriol. R.-P.. New genus and new species of Cirripedia (Chthamalidae, Tetraclitidae, Archaeobalanidae and Balanidae) from the Middle Miocene of the faluns of Touraine (France). Zootaxa. 2008. 1675. 31–48.
2. Buckeridge. J. S.. Fossil barnacles (Cirripedia: Thoracica) of New Zealand and Australia. New Zealand Geological Survey Paleontological Bulletin. 1983b. 50.
3. Buckeridge. J. S.. D. E. Lee. J. H. Robinson. A diverse shallow-water barnacle assemblage (Cirripedia: Sessilia) from the Oligocene of Southland, New Zealand. New Zealand Journal of Geology and Geophysics. 2014-02-19. 10.1080/00288306.2013.873472. free.