Tone (1970) 16: 135-142. 135

A S U B F O S S I L L A N D S N A I L F A U N U L E F R O M K A W H I A

by P . G . P a r k i n s o n *

S U M M A R Y

An extensive deposit of sub foss i l land s n a i l s at Andersons Bluf f , near the Hamilton Junior N a t u r a l i s t s ' C l u b ' s reserve on the K a w h i a Harbour, i s descr ibed and d i s c u s s e d with reference to the means of preservation of land mol luscs in s u b f o s s i l deposi ts .

I N T R O D U C T I O N

In 1966 a large deposit of s u b f o s s i l land s n a i l s was d iscovered at Andersons Bluf f , a large l imestone exposure on the farm of Mr. G . Anderson of K a w h i a . I n i t i a l excavat ions revealed a wel l -preserved faunule of great d ivers i ty which was in several ways d is t inct from the faunule of the adjacent reserve, T e K a u r i P a r k . Further excavat ions on this and nearby s i tes revealed a faunule of some s ixty spec ies of s n a i l s . T h i s paper descr ibes the work carr ied out at Andersons B lu f f and brief ly compares the results obtained with the extant Te K a u r i Park faunule and with the faunules of other s u b f o s s i l deposi ts in the area. T h i s work formed the bas i s for a paper entered by the author in the ' R o y a l Society of New Zea land Centennia l Awards for Secondary School Science 1968' competi t ion.

A N D E R S O N S B L U F F

Andersons B lu f f i s a ridge of Ol igocene l imestone about 200 ft. in length at the western end of a long ridge. The south-eastern end contains a short three-chambered cave. Another cave , containing moa remains but no s n a i l s , occurs in a l imestone outcrop nearby. Moa remains have not been found anywhere at Andersons Bluf f . The bluff has been bush-c lad in the past but the surrounding land has been taken for farming and there are now few trees le f t . The bluff no longer supports a l i v i n g s n a i l faunule and it appears that the disappearance of the l i v i n g faunule, the last formation of sub foss i l deposi t , and the convers ion of the area to farmland, were s imultaneous. Weathering i s fast eroding the soft l imestone , e s p e c i a l l y on the lower slopes of the bluff and any deposi ts which may have been present on the lower s lopes in the past have been washed away. Depos i ts are s t i l l numerous on the top of the bluff and on i t s eastern end where they occur under v i r tua l ly every loose s lab of rock and in many smal l ho l l ows and crev ices in the boulders. The d is tr ibut ion of s ing le spec ies in the deposits is d iscont inuous and may indicate that the deposi ts were formed over a long period or that microhabitats at the bluff changed rapidly ( F i g s . 2a , 2b).

•Department of Botany, University of Auckland.

FIG. 1: Map of Te Kauri Park showing major subfossil land snail deposits.

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FIG. 2a: Andersons Bluff from the East end.

FIG. 2b: Sketch of Andersons Bluff showing chief features.

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FIG. 3: Suggested origin of the Andersons Bluff deposits. 1. Stream wears its bed into limestone, l a . Cavity forms around limestone joint. 2. Emergence of limestone ridge in bush. 2a. Snails breed in the enlarged crevices and joints

and deposit forms, as the soil level drops. 3. Bush removed; erosion increases, mud slips form

deposits weathered from all parts of the bluff except the top.

3a. Later erosion lowers the soil level. Snails locally extinct: This is the present situation at Andersons Bluff.

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F O R M A T I O N O F T H E D E P O S I T S

A great many smal l land s n a i l eggs (part icular ly of the paryphantid genus Delos) are preserved in the bluff deposits suggest ing that the snails retired to rock c rev i ces for breeding. T h i s contention i s reinforced by the overwhelming numbers of juveni le s h e l l s and protoconches found in the deposi ts . I have noticed that bushc lad l imestone i s often a good collecting p l a c e for l i v e s n a i l s and that these tend to aggregate in crevices and under ledges. A suggested or ig in for the depos i ts , based upon these observations i s presented in F igure 3.

T H E E X C A V A T I O N O F A N D E R S O N S B L U F F The deposit was scraped away by hand so that large s h e l l s were not

crushed, then dried and s ieved to remove large s h e l l s , stones and plant debris . Sieved grit was shaken in a musl in c loth to s i f t out dust, l e a v i n g s h e l l s and sandy loam beh ind . T h e c lo th used was fine enough to retain even the smal les t protoconches. The grit was then passed through an ordinary kitchen s ieve to sort the s h e l l s into two s i z e grades. These were returned to the c loth and washed separately in co ld water. The coarse grade was dried and sorted but the fine grade was taken to c lean water and left to soak a short time, after which the smal l s h e l l s were decanted, dried and sorted.

L A N D S N A I L C H E C K L I S T S

To indicate re lat ive abundance the fo l l owing abbreviat ions are u s e d a: abundant

co: common oc: o c c a s i o n a l

r: rare

T H E A N D E R S O N S B L U F F F A U N U L E Omphalorissa purchasi (Pfeiffer) a Cytora cyiora (Gray) r, one specimen C. torquilla (Suter) r, local Liarea hochstetteri carinella (Pfeiffer) r Potamopyrgus zelandiac (Gray) r Otoconcha dimidiata (Pfeiffer) oc Thalassonelix ziczac (Gould) r, one specimen Allodiscus adriana (Hutton) doubtful record A. dimorphus (Pfeiffer) oc A. miranda (Pfeiffer) oc Thermia subincarnata (Suter) r Serpho kivi (Gray) r Therasiella. celinde(Gra<,) co

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Phcnacohelix ponsonbyi (Suter) a P. giveni Cumber a P. pilula (Reeve) oc Suteria ide (Gray) co Flammulina crebriflammis (Pfeiffer) co F. perdita (Hutton) co Champa (Ptychodon) hectori (Suter) a C. (Ptychodon) pseudoleiodon (Suter) co C. (Ptychodon) tau (Pfeiffer) oc C. (Ptychodon) varicosa (Pfeiffer) a C. (Ptychodon) colensoi (Suter) a C t Ptychodon) buccinella (Reeve) r C. (Ptychodon) reeftonensis (Suter) r C. (Subfectola) caputspinulae (Reeve) a C. (Mocella) eta (Pfeiffer) a C. (Mocella) aff. prestoni (Sykes) r C. (Geminoropa) microrhina (Suter) r C. (Geminoropa) huttoni (Suter) co C. (Aeschrodomus) stipulata (Reeve) co Charopa (Charopa) coma (Gray) oc C. (Charopa) pilsburyi (Suter)' r C. (Charopa) anguiculus (Reeve) co Laoma microreticulata Suter one specimen L . leimonias (Gray) co L. pirongaensis (Suter) co L. marina (Hutton) co L. trigone (Gray) co L. fulgurata Suter r L . ariel (Hutton) co L. mariae (Gray) r Paralaoma sericata (Suter) co P. raricoStata (Suter) a Tornatellinops novoseelandica (Pfeiffer) co Rhytida greenwoodi (Gray) oc, local Schizoglossa novoseelandica (Pfeiffer) r Delos coresia (Gray) r D. Jeffreysiana (Pfeiffer) a

T H E LIVING L A N D SNAILS O F T E KAURI P A R K

Omphalarissa purchasi (Pfeiffer) r Cytora cytora (Gray) r, local C. aff. pallida (Hutton) r, found once Liarea hochstetteri carinella (Pfeiffer) oc Potamopyrgus zelandiae (Gray) oc, local Otoconcha dimidiata (Pfeiffer) r Thalassohelix ziczac (Gould) co Allodiscus adriana (Hutton) r A. dimorphus (Pfeiffer) oc A. miranda(Pfeiffer) oc Thermia subincarnata (Suter) r, found once Serpho kivi (Gray) co Therasiella celinde (Gray) co Phenacohelix ponsonbyi (Suter) a P. giveni Cumber a P. pilula (Reeve) r

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Suteria ide (Gray) c ° Flammulina perdita (Hutton) co F. zebra (Le Guillou) r Charopa (Ptychodon) Aectori (Suter) co, in Freycinetia

banksn C. (Ptychodon) pseudoleiodon (Suter) oc C. (Ptychodon) tau (Pfeiffer) r C. (Ptychodon) varicosa (Pfeiffer) r C. (Ptychodon) colensoi (Suter) r, found once C. (Charopa) coma (Gray) co C. (Charopa) anguiculus (Reeve) co C. (Charopa) pilsburyi (Suter) r C. (Aeschrodomus) stipulata (Reeve) one specimen C. (Subfectola) caputspinulae (Reeve) co C. (Mocella) eta (Pfeiffer) oc C. (Mocella) aff. prestoni (Sykes) r Laoma leimonias (Gray) r L . pirongaensis Suter oc

marina (Hutton) co arte! (Hutton) co

L. erigone (Gray) a L. fulgurata Suter oc, local L. glabriuscula (Pfeiffer) oc, local L . mariae (Gray) a L . moellendorffi (Suter) r, found once Rhytida greenwoodi (Gray) oc Schizoglossa novoseelandica (Pfeiffer) oc Delos coresia (Gray) oc D. Jeffreysiana (Pfeiffer) oc Paralaoma raricostata (Suter) r, found twice

Note: Subfossils of Charopa (Mocella) segregata (Suter) have also been found in the area.

C O M P A R I S O N O F T H E C H E C K L I S T S

Although the faunae in both c h e c k l i s t s are s i m i l a r , the relat ive abundance of part icular s p e c i e s i s seen to be quite different. T h i s feature i s t y p i c a l of a l l the deposits examined and so is presumably related to the e co l og i ca l condit ion of the s i te when the deposit was being formed. When more i s known of the preferred environments of s n a i l s s tudies of sub foss i l s may be useful in reconstructing the b i o l o g i c a l history of the s i t e s . The study i s a lso useful in construct­i n g the range of genera and spec ies . When time i s short co l l ec tors tend to seek s n a i l s in s i tes w e l l known to be productive e.g. Rhopalostylis sapida debr is . T h e use of sub foss i l samples however gives a more general se l e c t i on of the fauna of an area under examination. A t Te K a u r i P a r k , s n a i l c o l l e c t i n g had been i n progress for several years before the s u b f o s s i l s were found and the extant faunule was bel ieved to consist of about thirty spec ies only . After the s u b f o s s i l s had been ident i f ied a general s n a i l census confirmed the presence of many spec ies which had previous ly been overlooked.

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A s u b f o s s i l deposit at Waitomo produced specimens of Pary-phanta (Powelliphanta) and thus increased the northern range of the sub-genus by some 250 mi l e s .

There i s no evidence for the age of the deposi ts at Andersons B l u f f . A s the s h e l l s are w e l l preserved it seems they are not very o ld and the oldest parts of the deposit probably do not date back more than a few centuries . No new spec ies or d i s t i n c t i v e forms have been found and there i s no reason to suppose that the s u b f o s s i l s w i l l c lar i fy the evolut ion of the land pulmonates.

A C K N O W L E D G E M E N T S

I w i s h to thank a l l those who took part in the Te K a u r i Park land s n a i l census of 1968 and who provided specimens for my examination. I am part i cu lar ly grateful to Mr. C . Templar and Mr. S. Easterbrook-Smith for their help in c o l l e c t i n g and sort ing s n a i l s , and to Mr. F . M . C l imo for h is help in check ing ident i f i ca t ions and for encouragement.

I thank the R o y a l Society of New Zealand for a l l o w i n g me to reproduce part of my report for publ i cat ion .

R E F E R E N C E S

CLIMO, F . M. 1969

1970

P O W E L L . A . W . B . 1962

SUTER, H. 1913

Classification of New Zealand Arionacea (Mollusca: Pulmonata) II.A Revision of Charopa subgenus Ptychodon Ancey 1888. Rec. Don. Mrts. Wellington 6.(14): 175-258.

Classification of New Zealand Arionacea (Mollusca: Pulmonata) III.A Revision of the genus Charopa Albers 1860 (excluding sub­genus Ptychodon Ancey 1888), Phenacharopa Pilsbury 1893 and Flammocharopa n.gen. (Endodontidae: Endodontinae). Rec. Dom. Mus, 6.(18): 285 - 366.

"Shells of New Zealand. " Whitcombe & Tombs

"Manual of the New Zealand Mol lusca . " Govt. Printer, Wellington.