GNS Science

Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)

New Zealand Cenozoic Mollusca

Sassia (Sassia) n. sp. A


(Pl. 4q): GS12173, CH/f478, neck of Tarawhenua Peninsula, Pitt Island, Waipawan (GNS)

Beu & Maxwell (1990): Chapter 6; p. 96; pl. 4 q.

Synonymy: Sassia (Sassia) n. sp. A, Beu & Maxwell 1990, p. 96, pl. 4q.

Classification: Ranellidae: Cymatiinae

Description: Shell 26-32 mm high (large for such an early species of the subgenus), relatively tall and narrow, with low, narrow varices at each 0.67 whorl down whole teleoconch, spire about equal in height to aperture and canal, whorls almost evenly rounded, and a moderately long, open siphonal canal directed weakly to left (incomplete in all material). Sculpture of simple, even, moderately prominent, cancellate spiral cords and axial costae, forming low nodules at their intersections, the sutural ramp and sculptural interspaces bearing several low, indistinct spiral cords and many fine growth ridges. Aperture oval; interior of outer lip weakly reflected over terminal varix, 6 nodules (the uppermost the largest) on inner edge, and with a shallow posterior sinus at the top; inner lip bearing 2 low parietal ridges, a nodule on centre of columella, and a row of 3 low, slightly oblique nodules on base of columella. Protoconch incomplete on available material, small, turbiniform, of at least 2.5 smooth, inflated whorls.

Comparison: This new species is a simply sculptured, typical but relatively large, early ("primitive") species of Sassia, resembling such European Paleocene species as S. faxensis (Ravn), but differing in its larger size, taller spire, and longer anterior canal (Tritonium fenestratum Ravn 1902, p . 22, pi. 2, fig. 7, 8, not of G. Vincent, 1878; renamed Triton faxense by Ravn 1933, p. 58, pi. 6, fig. 7a, b, 16a, b). Very few of the many Cretaceous species previously referred to "Triton" (or other early generic names in Ranellidae) really belong in this family, and the few that do are all simple, primitive Sassia species closely resembling S. faxensis and the Pitt Island Early Eocene species (Beu 1988, p. 86, 87). The sole exception we are aware of is Distorsio praegranosa (Cottreau), discussed below. The fossil record therefore shows that only Sassia (among true Ranellidae) occurs in Cretaceous rocks, appearing first during the Turonian Stage, and all Cenozoic and living Ranellidae have apparently descended from Sassia.

A similar but shorter and wider shell with a more excavated abapertural variceal face is present in NZGS collections from the View Hill Volcanics, White's Creek, Eyre River, Canterbury (Mangaorapan). Primitive Sassia species were probably widespread in New Zealand on volcanic hard-ground substrates during Paleocene and Eocene time. S. decagonia (Bortonian) has more angled whorls and much sparser sculpture, and the other new species described below (PI. 7 t; McCulloch's Bridge, South Canterbury; Kaiatan) has more angled whorls and much more complex apertural armature than the Paleocene and Early Eocene species.

Distribution: Waipawan (Early Eocene), Red Bluff Tuff, "Rocky Side" Bay, neck of Tarawhenua Peninsula, Pitt Island, Chatham Islands; moderately common.

Cite this publication as: "A.G. Beu and J.I. Raine (2009). Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990). GNS Science miscellaneous series no. 27."
© GNS Science, 2009
ISBN 978-0-478-19705-1
ISSN 1177-2441
(Included with a PDF facsimile file copy of New Zealand Geological Survey Paleontological Bulletin 58 in CD version from: Publications Officer, GNS Science, P.O. Box 30368 Lower Hutt, New Zealand)


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