GNS Science

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

New Zealand Cenozoic Mollusca

Genus Gadila Gray, 1847



scale

(Pl. 57j): Cadulus (Gadila) n. sp.; GS9517, I40/f9805, Campbell Park School, Waitaki Valley (Waitakian)

Beu & Maxwell (1990): Chapter 17; p. 391; pl. 57 j.

Classification: Gadilidae

Description: Length 3-10 mm, slender, distinctly curved, ventral side convex, dorsal side gently concave; widest part of shell variable in position, just behind aperture in some species, near middle in others. Shell polished, typically without sculpture apart from growth lines, but some species with distinct transverse rings. Apex simple, without slits or notches.

Comparison: Two major groups of scaphopods are recognised, primarily on the basis of anatomical differences, the Dentalioida and the Gadiloida (= Siphonodentalioida). Members of the former group are typically rather large (although they include many small species), include many strongly sculptured species (as well as smooth forms) and have the greatest diameter at the aperture. Those in the Gadiloida are relatively small (typically less than 10 mm in length, although some grow to 25-30 mm), are usually smooth (a few have distinct longitudinal or transverse sculpture), and with a few exceptions have the greatest diameter somewhere behind the aperture.

Because of their generally large size, species of the Dentalioida are usually well represented in collections, whereas the Gadiloida are often overlooked, even though they occur throughout the Cenozoic in New Zealand. To date only five fossil species of Gadiloida have been described from New Zealand, but a considerable number of undescribed species is known. Most of these belong in the Gadilidae, members of which have a constricted aperture, but a species of Entalina Monterosato, 1872 — which is characterised by having a Dentalium-like shell of polygonal cross-section with distinct longitudinal sculpture and a non-constricted aperture — is recorded from the Kaiatan at McCulloch's Bridge, South Canterbury (Maxwell 1992, p. 187).

Some authors (e.g. Ludbrook in Moore 1960, p. 140; Emerson 1962, p. 476-480) have recognised a single genus Cadulus in what is now known as the Gadilidae (i.e. excluding Siphonodentaliidae), and subdivided this into several subgenera. More recently (Starobogatov 1984; Palmer 1984) some of these taxa have been elevated to generic rank. Beu & Maxwell (1990) accepted Striocadulus Emerson, 1962 as a full genus because it is amply distinguished from the other gadilids by its comparatively large size, and in having distinct longitudinal sculpture — they considered it to include two fossil species, S. prosperus and S. delli. However, they chose to recognise Cadulus in a broad sense because some fossils are too imperfectly known to assign to an appropriate taxon, and also because some species (including the extant C. delicatulus Suter, 1913 and C. teliger Finlay, 1926) do not satisfactorily fit into any available taxon.

Cadulus (sensu stricto) is characterised by having a short, strongly inflated, cask-like shell in which the dorsal side is flat or convex, and in having a simple apex (i.e. lacking slits or notches). It may be represented in New Zealand by an undescribed species from Pakaurangi Point (Otaian). Cadulus (Gadila) differs in having a slender shell with a distinctly concave dorsal side. Cadulus (Polyschides) Pilsbry & Sharp, 1898 has four prominent (and in some species, two additional weaker) apical slits, and is recorded from the Kaiatan at McCulloch's Bridge, South Canterbury (Maxwell 1992, p. 188). It should be emphasised, however, that the New Zealand scaphopod fauna is still poorly known so these taxa almost certainly have longer stratigraphic ranges than these occurrences would indicate. In the most recent works on scaphopods (e.g., Steiner & Kabat 2001, 2004; Scarabino 2008) these former subgenera of Cadulus are recognised as genera, each containing a large number of tropical Pacific species, and the number of genus-level taxa is greatly increased.

Distribution: Kaiatan-Clifdenian, New Zealand; cosmopolitan, Cretaceous-Recent.


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)

References

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