Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)
(Pl. 1e): GS10195, I44/f8486, Boulder Hill, Wangaloan (GNS)
(Pl. 1h): GS10195, I44/f8486, Boulder Hill, Wangaloan (GNS)
Beu & Maxwell (1990): Chapter 5; p. 78; pl. 1 e, h.
Synonymy: Glycymeris concava Marshall 1917, p. 459; Glycymeris (Glycymerita) concava
Type species of Glycymerita Finlay and Marwick, 1937
Classification: Glycymerididae: Glycymeridinae
Description: Moderately large for family (length 50-60 mm), subquadrate, strongly inflated, robust. Umbones prominent, posterodorsal margin longer than anterodorsal margin; anterior margin gently convex, ventral margin strongly convex, posterior margin distinctly truncate. Radial sculpture of about 45 costae, those near anterior and posterior ends narrow and rounded, others flattened with sharply defined margins. Well preserved shells with numerous fine, submerged threads as well. Hinge highly variable, some specimens with long, almost horizontal teeth, others with short, steeply inclined teeth. Ventral margin strongly crenulate.
Comparison: Glycymerita concava is readily distinguished from younger species of Glycymerita by its very well-defined, square-cut radial costae. Glycymerita is usually classed as a subgenus of Glycymeris, but it includes a group that has been distinct from Glycymeris since Late Cretaceous time, and its morphology differs sufficiently from that of Glycymeris (in having a subquadrate rather than a subcircular shell, and in its relatively prominent radial sculpture) to warrant generic rank in this conservative family.
Glycymerita ranges from Late Cretaceous (G. selwynensis (Woods, 1917)) to early Nukumaruan in New Zealand, and is also recorded from Europe and California (Newell in Moore 1969, p. 267). The Neogene New Zealand species are typically of large size (e.g. G. rangatira, Pl. 28g, h), although Argentinian species are even larger. All records of the genus are from shallow-water (inner or middle shelf) assemblages.
Distribution: Wangaloan, Wangaloa Formation, Wangaloa (type); Boulder Hill (common at both localities); ? Kakanui River.
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
(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)