Pteropoda (Mollusca, Gastropoda, Euthecosomata) from the Miocene Taumarunui Formation of New Zealand

ABSTRACT

Three pteropod species are recorded from late Waitakian–Otaian (Aquitanian–early Burdigalian) rocks of the Taumarunui Formation (Mahoenui Group) outcropping southwest of Taumarunui, King Country, New Zealand. Two of these, Limacinidae sp. and Clio sp. have been recorded in open nomenclature due to poor preservation. The third, Clio triplicata Audenino, 1899, was previously known only from Miocene deposits in Europe and offers possibilities for long-distance correlation.

KEYWORDS:

• Aoloplanktic Mollusca
• Clio sp
• Clio triplicata
• Limacinidae
• long-distance correlation
• Miocene
• New Zealand
• Taumarunui Formation

Introduction

The pteropod fossils recorded here were found in Taumarunui Formation strata (Figures 1, 2A–C) exposed in Herlihy Bluff (38.9171°S, 175.2316°E) on State Highway 43, c. 5 km southwest of Taumarunui, King Country, central North Island. The strata have a regular alternation of dm-bedded turbiditic sandstones and hemipelagic mudstones (Kamp et al. 2004). The undersides of the sandstone slabs have ripples, load casts or flute marks. Fossils are mostly occasional foraminifera and vegetal debris (leaf and wood fragments).

Figure 1. Location of Herlihy Bluff along the Whanganui River, southwest of Taumarunui, King Country, North Island, New Zealand. New Zealand Fossil Record Electronic Database, fossil record number S18/f0056. Basic map data from GoogleEarth.

Figure 2. Herlihy Bluff outcrop of Taumarunui Formation on State Highway 43. A, Overview. B, Debris in the trench at the base of the section. C, Detail of Figure 2B (hammer head is 16.5 cm). Photographs: Lynette L. Hellyar. D, Concentration of poorly preserved Limacinidae sp. indet. on slab 2, Naturalis Biodiversity Center collection RGM 777 442a. E, Clio sp. indet. on slab 2. Naturalis Biodiversity Center collection RGM 777 442b. Photographs of Figure 2D and 2E: Ronald Pouwer.

During a visit to Herlihy Bluff on 30 April 2016 with the Auckland Geology Club, the second author found two slabs of fallen rock containing a large number of triangular fossils. They appeared to be rather poorly preserved holoplanktic Mollusca (Pteropoda) resembling the recent species Clio pyramidata Linné, 1767. Because that species had never been found on land as a fossil in New Zealand, the two slabs were sent to the first author in the Netherlands for identification.

A number of fossil pteropods have been recorded previously from New Zealand (Beu & Maxwell 1990; Janssen 2006; Maxwell 2009). The following Miocene species are now known (original and present-day names):

Family Limacinidae Gray, 1840

Spiratella atypica Laws, 1944 = Heliconoides atypicus (Laws, 1944); genus assignment changed herein on the basis of Janssen (2003)

Spiratella ferax Laws, 1944 = Heliconoides ferax (Laws, 1944); genus assignment changed herein on the basis of Janssen (2003)

Family Cuvierinidae Van der Spoel, 1967

Vaginella torpedo P. Marshall, 1918 = Cuvierina torpedo (P. Marshall, 1918); genus assignment changed by Janssen (2005, 2006)

Vaginella aucklandica Clarke, 1905 = Ireneia aucklandica (Clarke, 1905); genus assignment changed by Janssen (2006)

Clio (Creseis) urenuiensis Suter, 1917 = Ireneia calandrelli (Michelotti, 1847); genus assignment changed by Janssen (2005, 2006)

Ireneia nieulandei Janssen, 1995

Family Cavoliniidae Gray, 1850 (1815)

Vaginella inflata Hayward, 1981 = Vaginella depressa Daudin, 1800; synonymised by Janssen (2006).

Family Sphaerocinidae Janssen & Maxwell in Janssen, 1995

Lornia marwicki Powell, 1935 = Sphaerocina formai (Audenino, 1899); genus assignment and synonymisation by Janssen and Maxwell, in Janssen (1995)

In addition to these described species, there is unstudied fossil pteropod material, collected by the late Philip Maxwell and Andrew Grebneff, housed in the GNS Science collections at Lower Hutt. It is likely that additional species will be present in this material.

The study of the first two slabs from Herlihy Bluff resulted in the recognition of two pteropod species. Both were unfortunately too poorly preserved to identify with any degree of certainty. On a repeat visit to the bluff, the second author managed to collect two further slabs with better preserved pteropods, including a new record for the New Zealand Miocene.

Material and methods

Four slabs (numbered 1 to 4) from Herlihy Bluff were studied. Slab 1 is in the private collection of the second author. Slab 2 (Figure 3A–B) is in the Naturalis Biodiversity Center, Leiden, The Netherlands (RGM 777 442). Slab 3 was cut into two pieces, one is in the National Paleontological Collection at GNS Science, Lower Hutt, New Zealand (GS15834, TM9252) and the other is in the Naturalis Biodiversity Center (RGM 777 443). Slab 4 is also housed in the GNS Science collection (GS15834, TM9253). The site is registered in the New Zealand Fossil Record Electronic Database, fossil record number S18/f0056 (http://www.fred.org.nz). All specimens were collected by the second author. Slab 4 is the only one with numerous specimens on both sides. Some unrecognisable bivalve fragments are present on the back of slab 2. All specimens are poorly preserved, with the original shell material partly dissolved. No further preparation or preservation was done.

Figure 3. Slab 2 with numerous specimens of Limacinidae indet. and Clio sp. indet.. A, Overview. The framed part in Figure 3A is enlarged in Figure 3B; Naturalis Biodiversity Center collection (RGM 777 442). Photographs: Ronald Pouwer. B–D, Clio triplicata Audenino, 1899. B, Cast of ventral side, slab 4, GNS Science collection (GS15834, TM9253c). C, D, Casts of dorsal side, slab 3, GNS Science collection (GS15834, TM9252c) and Naturalis Biodiversity Center collection (RGM 777 443a), respectively. Photographs: Eduard F. de Vogel.

Age and paleoenvironment

The Taumarunui Formation is part of the Mahoenui Group (Glennie 1959) of late Waitakian (Lw)–Otaian (Po) age (Aquitanian–early Burdigalian, 23–18.7 Ma; Edbrooke 2005; Raine et al. 2015). One sample collected from Herlihy Bluff (S18/f15) by Topping (1978) contained 90% planktic foraminifera, which include well-preserved specimens of Globoquadrina dehiscens (Chapman et al. 1934) (Lw–late Miocene), Globigerina woodi Jenkins, 1960 (middle Lw–Pliocene), Globigerina woodi connecta Jenkins, 1960 (late Lw–Po) and Catapsydrax dissimilis (Cushman & Bermúdez 1937) (Oligocene–Po) confirming a late Waitakian–Otaian age for the pteropod-bearing rocks. The small benthic foraminiferal fauna is most similar to early Miocene association G from the Waitemata Basin, 400 km to the north, which is inferred to have lived at bathyal depths with low carbon flux and oxic to suboxic bottom conditions (Hayward & Triggs 2016). The presence of specimens of Eggerella bradyi (Cushman 1911) and Scallopostoma ovicula (d’Orbigny 1826) with upper water depth limits of 750 and 900 m, respectively (Hayward & Triggs 2016) suggests probable lower bathyal depths (1000–2000 m). The 90% planktic foraminifera provide an estimate of 950 ± 100 m water depth based on a regression equation relating modern planktic per cent values around New Zealand to water depth (Hayward & Triggs 2016). All the above proxies for paleo-water depth for the Taumarunui Formation at Herlihy Bluff give depths in the order of 900–1500 m.

Systematics

Phylum Mollusca Linnaeus, 1758

Class Gastropoda Cuvier, 1795

Subclass Heterobranchia Burmeister, 1837

Order Thecosomata de Blainville, 1824

Suborder Euthecosomata Meisenheimer, 1905

Superfamily Limacinoidea Gray, 1847

Family Limacinidae Gray, 1847

Limacinidae indet.

Figure 2D

Material examined: Hundreds of poorly preserved specimens on all four collected slabs; Hellyar, Naturalis Biodiversity Center (RGM 777 442–443) and GNS Science collections (GS15834, TM9252a–TM9253a).

Description: All specimens appear as very small white items. A few of them can be recognised as sinistrally coiled limacinids but do not show any further morphological details, apart from one or two specimens that possibly have a peripheral belt.

Discussion: It cannot be decided whether the specimens from Herlihy Bluff are conspecific with one or both limacinid species known from the New Zealand Miocene (see above). Both species belong to the genus Heliconoides, meaning that in the adult stage they possess well-developed reinforcement structures on their apertural margin. Despite the many specimens available, such structures could not be recognised. In one or two specimens, however, a peripheral belt as seen in the species Heliconoides inflatus (d’Orbigny 1834–1847; see Sherborn & Griffin, 1934 for publication dates) seems to be present, but without any degree of certainty. The species H. inflatus is one of the most commonly occurring pteropod species in the present-day tropical–subtropical oceans and it is known to be present from the late Oligocene onwards. Although it has not been recorded previously from the New Zealand Miocene, it is present in somewhat younger sediments of Balcombian to Bairnsdalian (=Langhian to Serravallian) age in southern Australia (Janssen 1990a). Its occurrence here seems quite acceptable but needs confirmation by well-preserved specimens.

Family Cliidae Jeffreys, 1869 (ICZN, 2006. Opinion 2133)

Genus Clio Linné, 1767

Clio triplicata Audenino, 1899

Figure 3C–E

Table

*1899	Clio triplicata Audenino, p. 106, pl. 5, fig. 4a–e.
1972	Clio triplicata Audenino, 1899; Robba p. 496, pl. 58, fig. 1, 2, 13; pl. 59, fig. 1–7.
1995	Clio triplicata Audenino, 1897 (sic); Janssen, p. 93, pl. 8, fig. 1–6 (with additional synonymy).

Type material: Lectotype in Museo Regionale di Scienze Naturali, Torino, Italy, registration number TTI 21.1.1 (internal mould and cast of ventral side), illustrated in Janssen (1995, pl. 8, fig. 1; herein copied as Figure 4).

Figure 4. Clio triplicata Audenino, 1899; lectotype; Monte dei Cappuccini, Torino, Italy. Collection Museo Regionale di Scienze Naturali, Torino, Italy, registration number TTI 21.1.1, height of internal mould 14.6 mm. A, Dorsal view. B, Ventral view of mould. C, External cast of ventral side (after Janssen 1995, pl. 8, fig. 1a–c).

Figures 3–4

Type locality: Monte dei Cappuccini, Turin, Turin Hills, northern Italy (Complesso di Baldissero Formation; middle Miocene, Langhian).

Material examined: Three specimens: one cast of ventral shell part on slab 4 (Figure 3C) in the GNS Science collection (GS15834, TM9253c); two casts of dorsal shell part on cut pieces of slab 3 (Figure 3D–E), one in the GNS Science collection (GS15834, TM9252c), one in the Naturalis Biodiversity Center collection (RGM 777 443a), respectively.

Description: Shell triangular, with apical angle of c. 50°. Dorsal shell part moderately convex with three strong radial ribs, central one slightly wider than lateral ones. Ventral part with single flattened central rib, slightly wider than lateral zones. Lateral carinae and protoconch not preserved in the present specimens.

Discussion: Previously, Clio triplicata was exclusively known from European localities. It was recorded from early to middle Miocene (Aquitanian to Langhian) localities in Italy (Robba 1972; Janssen 1995, 2012), and also from some Paratethys localities (Zorn 1999). Therefore, its occurrence in the Miocene of New Zealand is surprising, although it is by no means the only example of such disjunct distribution. Several of the New Zealand Miocene pteropod species, as listed in the Introduction, were also originally described on the basis of European material (i.e. Ireneia calandrelli, I. nieulandei, Vaginella depressa, Sphaerocina formai). Similar examples are known from the South Australian Cenozoic pteropod assemblages (Janssen 1990a, 1990b). Another example from New Zealand is the early Pliocene Cavolinia grandis (Bellardi 1873), originally described from northern Italy, but recorded from the South Island, West Coast, McKay Creek, Kaniere Valley (Pliocene, Waipipian, Bluebottom Formation) in the unpublished MSc thesis of Almond (1980, p. 231) as Cavolinia tridentata f. zelandica Almond, nomen nudum (further described and illustrated in Janssen 2000).

Clio sp. indet.

Figures 2E, 5A–E

Material examined: Abundant specimens on all four available slabs; Hellyar, Naturalis Biodiversity Center (RGM 777 442–443) and GNS Science (GS15834, TM9252b–TM9253b) collections.

Description: All specimens are poorly preserved with partly dissolved shells that appear as small triangular white spots on the slab surfaces. In some of the larger specimens, the lateral carinae demonstrate a slightly concave shape, resembling the species Clio pyramidata Linné, 1767, which explains why initially the specimens were thought to represent that species. All specimens are completely flattened. Dorsal or ventral sides of the shell cannot be distinguished and protoconchs are not preserved. Even in a flattened state the shells should show the radial ribbing of C. pyrimidata, which is not the case. Specimens appear to have a completely smooth shell on both ventral and dorsal sides. Clio pyramidata is known exclusively from late Miocene onwards, which makes an occurrence in these early Miocene rocks improbable Figure 5.

Figure 5. Clio sp. indet. A–E, Some details of slabs 1 and/or 2. Photographs: Tim Saunderson.

Discussion: We know of just a single comparably triangular Clio species without dorsal and ventral ribbing, which is the middle Miocene (Langhian) Clio saccoi Checchia-Rispoli, 1921, described from the Lago di Varano Formation of the Gargano Peninsula in central Italy. In that species, both ventral and dorsal shell parts are slightly convex with narrow concave zones along the carinae. The Taumarunui specimens do not show even a trace of that morphology and are not thought to belong to that species, which is only known from European localities. This leads to the (premature) conclusion that the Taumarunui specimens represent an undescribed Cliidae species but the material is far too incomplete to formally describe and name it.

Conclusions

Early Miocene (late Waitakian–Otaian; Aquitanian–early Burdigalian) sedimentary rocks of the Taumarunui Formation, Mahoenui Group, exposed c. 5 km southwest of Taumarunui, central North Island, New Zealand, yielded three species of Pteropoda (Gastropoda, Euthecosomata), the two most abundant of which are recorded in open nomenclature as Limacinidae sp. indet. and Clio sp. indet. A few other specimens are identified as Clio triplicata Audenino, 1899, a species originally described from northern Italy and previously known only from Europe.

It is suggested that the Limacinidae sp. might (probably in part) belong to Heliconoides inflatus (d’Orbigny 1834–1847; see Sherborn & Griffin, 1934 for publication dates), a widespread species with a stratigraphic range of late Oligocene to recent, also known from the Miocene of southern Australia. The Clio sp. cannot be related with any confidence to known cliid species and might be undescribed. Its state of preservation, however, prevents introduction of a new taxon.

Interesting from a paleoenvironmental point of view is the fact that at the studied locality pteropods were only found to be present on a very restricted number of sediment slabs, but when present occurred in large numbers of specimens. This indicates that pteropod populations only occasionally entered the basin, in spite of the fact that a bathyal paleodepth is accepted for the Taumarunui Formation. Such occasional occurrences can be explained by short-term changes in ocean currents, possibly under the influence of climatic conditions (e.g. storms).

The occurrence of Clio triplicata represents a further example of disjunct pteropod distribution that may have important implications for long-distance correlation. In the present-day pteropod biogeography, many species occupy large parts of the world’s oceans, usually according to climatic zones (such as subarctic, temperate, bisubtropical or tropical). Very remote occurrences of species therefore not only offer possibilities for chronostratigraphical correlations, but also indicate comparable paleoenvironmental conditions. Although at present the number of such long-distance correlations on the basis of pteropods is still restricted, they are potentially very useful in these respects and may basically be compared with other such pelagic organisms, like planktic foraminifera and calcareous nannoplankton.

Acknowledgements

The authors are grateful to Bruce Hayward (Geomarine Research, Auckland, New Zealand) for supplying the data on age and paleoenvironment, as well as for much appreciated linguistic help. Alan G. Beu (GNS Science, Lower Hutt, New Zealand) is thanked for his interest and critical reading of an earlier version of the manuscript. Ronald Pouwer, Eduard F. de Vogel (both Naturalis Biodiversity Center, Leiden, The Netherlands) and Tim Saunderson (Auckland, New Zealand) took care of most of the photographic work. Marjan Helwerda (also of Naturalis Biodiversity Center) cut one of the slabs to facilitate housing of voucher specimens in two different institutes. We thank Bruce Marshall (Museum of New Zealand Te Papa Tongarewa, Wellington, New Zealand) and an unknown second reviewer, as well as the editors of this journal, for critically reading the manuscript and useful comments. Associate Editor: Dr Kari Bassett.

Disclosure statement

No potential conflict of interest was reported by the authors.