Penion haweraensis

Penion haweraensis is an extinct species of sea snail, a marine gastropod mollusc in the family Austrosiphonidae.^[1] Fossils of the species date to late Pliocene strata of the Tangahoe Formation in New Zealand.

In the original description, Powell described the species as follows:

The fossil species is most distinctive in its early whorls, which are crossed by distant broad axial folds, nine to thirteen per whorl. These persist over all the post-nuclear whorls, although subobsolete in development. Typical mandarina never has axials on the later whorls, although there are from eighteen to twenty-one closely spaced axial folds on the early spire whorls. Whorls estimated at about nine. The protoconch is missing in the holotype, but a paratype shows a well preserved nucleus of three whorls...the spiral cords, which number nine on the penultimate and about twenty-four on the body-whorl, show a tendency to widen rather than to become prominently elevated, as in mandarina. The true outline of the Hawera species is a little narrower than shown in the holotype, which has been subjected to dorso-ventral pressure in the matrix.^[3]

The holotype of the species has an estimated height of 123 mm (4.8 in), and a diameter of 58 mm (2.3 in).^[3] It can be distinguished from P. mandarinus due to having nine primary cords and one thread per interspace on the penultimate whorl, compared to 10-12 primary spiral cords and between 2-6 spiral threads per interspace in P. mandarinus.^[3]

The species was first described by A. W. B. Powell in 1931, who named the species Austrosipho (Verconella) haweraensis.^[3] As Austrosipho was synonymised with Penion in 1930,^[4] the current accepted name for the species is Penion haweraensis.^[1][5] Powell believed that the species was ancestral to P. mandarinus, due to similarities in form and size, but differentiated the species based on sculpture detail differences.^[3] In 1973, A. G. Beu synonymised Aeneator contractus with the species, finding that A. contractus was a juvenile form of the species.^[2]

The holotype was collected in January 1931 from near the mouth of Waihi Stream near Hāwera, Taranaki, and is held in the collections of Auckland War Memorial Museum.^[6][7]

This extinct marine species occurs in late Pliocene (Waipipian) strata of the Tangahoe Formation, primarily associated with the Taranaki and Manawatū–Whanganui regions of New Zealand.^[6] Fossils of the species have been found near Hāwera, South Taranaki,^[3] Martinborough in the South Wairarapa District,^[8] and near Masterton in the Masterton District.^[9][10]