FOSSILS

Marine fossils are known in New Zealand from 13 of the 15 major divisions of geologic time. Fossils belonging to the Silurian and Carboniferous periods have not been definitely recognised in the New Zealand succession.

The New Zealand fossil record is predominantly marine and most phyla of marine animals are represented; the record of terrestrial or freshwater life is extremely poor. As Phyla vary widely in their structure for preservation as fossils (hard-shelled creatures are more likely to be preserved than those with soft bodies), the fossil record at best only provides glimpses of the history of life in the past.

Of the marine Protozoa, Foraminifera are particularly well represented in the Upper Cretaceous and Tertiary of New Zealand, but older records are rare, owing to the hardness of the enclosing rocks. Scattered Lower Cretaceous faunas are known, and rare Jurassic and Permian faunas. The study of fossil Coccolithophorida and Radiolaria from New Zealand is yet in its infancy, but Coccoliths occur in the Upper Cretaceous and Tertiary, and Radiolaria in the Tertiary and Triassic (radiolarian cherts). Sponge remains (Porifera), mainly isolated spicules, are preserved in the Cambrian, Ordovician, Upper Cretaceous, Lower Tertiary, and Pleistocene, but they have been little studied. Receptaculites, a spongelike fossil, but of uncertain systematic position, is recorded from the Devonian of New Zealand. The fossil record of the Coelenterata in New Zealand starts in the Devonian, when Rugose and Tabulate corals flourished. Two types of coral assemblage characterise the New Zealand Permian: solitary, cool-water types in the Lower Permian, and reef-building, warm-water types in the Upper Permian. Apart from a conularid found in the Upper Triassic, the post-Permian records of coelenterates are from the Cretaceous and Tertiary rocks – a few Hydrozoa and Anthozoa and abundant Zoantharia (Scleractinia). Marine tube-forming Annelida are represented by tubes and shells. Not much work has been done on New Zealand fossil annelids, but two species have been described from the undifferentiated Triassic-Jurassic rocks of the main ranges of the North and South Island, and these may be of Triassic age. Other worm tubes are known from the Jurassic, Cretaceous, and Tertiary. Marine Arthropoda are well represented in New Zealand by Ostracoda and Cirripedia and by rarer Decapoda and Trilobita, but other Arthropoda have extremely poor fossil records and terrestrial groups are hardly represented at all apart from insects in late Quaternary deposits. The oldest New Zealand Ostracods are from the Cretaceous, and the group ranges throughout the Tertiary. Fossil Cirripedes occur in the Tertiary, and fossil Decapoda in the Lower and Upper Jurassic, Upper Cretaceous, and Tertiary. Phyllocarids (Leptostraca) are preserved in the Ordovician, and Trilobites in the Cambrian, Ordovician, and Devonian. Shelled Mollusca have the most complete record of all larger invertebrates, but land shells are not recorded as fossils in New Zealand before the Pleistocene, and freshwater groups are little known. Gastropoda range back to the Cambrian, but it is not until the Devonian that the first Pelecypoda appear.

From the Permian to the present day, each of the geologic periods in New Zealand is characterised by important pelecypod and gastropod faunas. About 240 genera of pelecypods and 570 gastropod genera have been described from the New Zealand Tertiary and Quaternary. The Scaphopoda, appearing first in the Triassic of New Zealand, are a minor element in the fossil invertebrate fauna, but become locally abundant in the Middle Tertiary. Because of their usefulness for dating and correlation, Cephalopoda are important Mesozoic fossils, but they are, on the whole, sparsely distributed in New Zealand. Rare Dibranchiata are known from the Upper Triassic, but none from the Lower Jurassic. The record improves in the Middle and Upper Jurassic, when belemnites are abundant and useful fossils. The Lower Cretaceous lacks belemnites, but distinctive belemnites characterise the Upper Cretaceous. Ammonoids occur in the Triassic and ammonites in most of the Jurassic stages and from some of those of the Cretaceous. Nautiloids are a minor element in the New Zealand fossil fauna and occur in the Mesozoic and Tertiary. Polyzoa are known from Devonian, Triassic, and Tertiary rocks. Brachiopoda are found in all of the geologic periods present in New Zealand. Primitive types (Atremata) are recorded from the Cambrian and Ordovician and more advanced forms from the Devonian. The Middle and Upper Jurassic and Cretaceous brachiopods are little known. Tertiary brachiopod faunas are of importance and rich faunas characterise the Oligocene. Echinodermata are rare in the Palaeozoic and Mesozoic of New Zealand. A carpoid is known from the Devonian, a cidarid (Echinoidea) from the Upper Triassic, an ophiuroid from the Upper Cretaceous, and asteroids from the Upper Jurassic and Upper Cretaceous. Good echinoid faunas are known from the Tertiary. New Zealand crinoids are not well known, but fragments occur in the Permian, Triassic, Upper Jurassic, and Tertiary. Primitive Chordata are represented in New Zealand by the graptolites (Stomochorda), found in the Ordovician.

Vertebrata have a sparse record in New Zealand and those that are preserved are mainly marine forms. Sharks and saw-sharks are represented by teeth, found in the Upper Cretaceous and Tertiary. Elephant Fish and Chimaerids have left some bone fragments in an Upper Cretaceous deposit. Rays have left rare grinding teeth and spines. Bones and scales of Teleost fish are occasionally preserved, but their commonest remains are otoliths. There is a single Pliocene record of a freshwater fish (Galaxias). Reptilia are known from Middle Triassic, Jurassic, and Cretaceous. In the late Cretaceous, large marine Mosasaurs and Elasmosaurs were not uncommon. No terrestrial dinosaurs (known in Australia and Patagonia) have been reported from New Zealand and the Tuatara (Sphenodon) of the present day has no fossil record before the Holocene. Birds have a poor fossil record, except for the penguins. The oldest moa bones (Dinornithi-formes) are Upper Miocene, and footprints, perhaps Apteryx, are about the same age. Extinct subfamilies of penguins (Sphenisciformes) are well represented from Lower Eocene to Oligocene, and there is a single Pliocene skeleton, but the living Spheniscinae are unknown before the late Pleistocene. A possible albatross bone is known from the Oligocene, but other flying birds have no record in New Zealand before the Pleistocene. Two groups of marine mammals are represented by scanty fossils: Cretacea in the Oligocene, Pliocene, and Pleistocene; Pinnipedia by a few bones from the Pliocene and Pleistocene.

Abundant coals, lignites, and peats, ranging in age from Jurassic to Recent, yield pollen grains and spores of land plants and provide a good basis for study of past plant life. Leaf, seed, and wood fossils, still not adequately studied, are a valuable supplement to the pollen record. The oldest recognisable plants in the New Zealand succession are fernlike fossils from the Permian of Southland. Middle Jurassic vegetation is represented by the well-known Curio Bay fossil forest of Waikawa, Southland; and Upper Jurassic vegetation by the Port Waikato plant fossils. Angiosperms arose and spread throughout the world at the end of the Lower Cretaceous, and angiosperm pollen grains of this age are known in New Zealand. Many good Tertiary floras are known, and in the Miocene they include fossil coconuts in Northland. Late Pliocene and Pleistocene floras reflect the gradual world-wide cooling in the Late Pliocene, followed by the oscillating climate of the Pleistocene. Marine and freshwater Algae have left no record, except for some marine calcareous forms and marine and freshwater diatoms.

Overseas Affinities

The study of plant and animal fossils has thrown light on the overseas relationships of the past life of New Zealand and has also given some idea of past climates. Cambrian and Ordovician faunas are virtually cosmopolitan in their affinities, but those of the Cambrian are close to those of Queensland, Manchuria, and the Baltic, and those of the Ordovician, to Victoria. Close relationship to Eastern Australia is also shown by the Devonian faunas, but again with cosmopolitan (Europe, North America) elements. Two definite faunas characterise the Permian – a Lower Permian fauna of brachiopods, pelecypods, and solitary corals, closely related to South-East Australia and, to a lesser extent, South Africa, South America, and India; and an Upper Permian warm-water fauna of fusulinid Foraminifera and reef corals with Indo-Pacific affinities. In the Triassic and Lower Jurassic, many brachiopods and pelecypods are confined to New Zealand or occur elsewhere only in New Caledonia; at this time the two countries were evidently isolated from the remainder of the Indo-Pacific. On the other hand, during the same time the ammonites, which probably lived in the surface waters, and pterioid pelecypods, such as Daonella, Halobia, Monotis and Rhaetavicula, which probably had pelagic larvae, were able to migrate freely, and cosmopolitan forms in these groups are found in New Zealand. The Middle Jurassic is characterised by the arrival of another pterioid pelecypod (Meleagrinella) and other pelecypods and gastropods from Indo-Pacific countries. Indo-Pacific affinities also persist into the Upper Jurassic. Climatically, in the Triassic and Jurassic New Zealand probably lay in the warm temperate zone. The Lower Cretaceous is represented by ammonites and some pelecypods of European affinities, other pelecypods of Southern Hemisphere affinities, and belemnites of Australasian affinities. The Upper Cretaceous faunas, in contrast, show strong southern (for example, South American) affinities. Cretaceous climate was probably temperate or warm temperate. Distinct South American affinities are continued into the lowermost Tertiary molluscan faunas, but accompanied by Indo-Pacific, Australasian, and endemic elements. These latter three elements are also found in the faunas of the remainder of the Tertiary and in the Quaternary. Throughout the Tertiary, temperatures in the New Zealand region were temperate or marginal tropical at best (Lower Miocene of Northland). The Pleistocene history of New Zealand is dominated by successive periods of cooling, which caused the extinction of warm-water forms and allowed the incoming of southern cool-water forms, although Indo-Pacific and Australian elements have continued to colonise.

by Graeme Roy Stevens, M.SC.(N.Z.), PH.D.(CANTAB.), Paleontologist, New Zealand Geological Survey, Lower Hutt.

MICROFOSSILS

Rivers and ocean waves constantly erode the land, and carry large quantities of sand and mud far out to sea to be deposited on the bottom in layers. Myriads of minute organisms, some living a benthic existence on the sea bottom, others floating in the upper layers of the sea as plankton, leave behind hard skeletons and shells which accumulate on the sea bed and become entombed in the sediment along with minute skeletal parts of larger organisms. Over a long period of time the layers of sediment become compacted and hardened to form rock strata, and may be exposed as dry land in a later geological period by withdrawal of the sea or uplift.

Rock strata, like the leaves of a book, are the pages of geological history which can be read by the micropaleontologist who studies assemblages of microfossils preserved in successive beds. As an archaeologist can assign artefacts to certain periods of human culture or a historian identify the characteristics of a period of history, so can a micropaleontologist tell in which geological age an assemblage of microfossils from a particular stratum was buried in the sea bed. Microfossils therefore help the field geologist to work out correctly the sequence of rocks and their geological structure in areas where the earth's crust is strongly contorted and dislocated or obscured by vegetation or young deposits.

New Zealand sedimentary rocks of upper Cretaceous and Tertiary age are rich in microfossils and there are numerous publications dealing with them.

Planktonic microfossils (freely floating in life) are widely distributed throughout the oceans by currents and similar assemblages of species are found in rocks of the same age in different parts of the world. Planktonic forms are therefore particularly useful for correlating rocks of the same age throughout the world and they help geologists to piece together more accurately the story of geological events in the earth's history.

Microfossils are used by oil exploration geologists in their surveys of possible oil fields. Their abundance and small size makes them especially easy to collect and store. A pea-sized piece of soft limestone or limey mudstone may contain many thousands of microfossils. Most soft limestones, mudstones or sandstones in New Zealand will yield Foraminifera, Ostracoda or Bryozoa if they are first well soaked and then washed over a fine sieve with holes of a millimetre or less in diameter.

by Norcott de Bisson Hornibrook, M.SC., F.R.S.N.Z., Senior Principal Scientific Officer, New Zealand Geological Survey, Lower Hutt.

• The Tertiary Cheilostomatous Polyzoa of New Zealand, Brown, D. A. (1952)
• New Zealand Geological Survey Paleontological Bulletin 18, Tertiary and Recent Marine Ostracoda of New Zealand, Hornibrook, N. de B. (1952)
• New Zealand Geological Survey Paleontological Bulletin 34, Tertiary Foraminifera from Oamaru District (N.Z.), Hornibrook, N. de B. (1961)
• Introduction to Microfossils, Jones Daniel, J. (1956).

PLANT FOSSILS – PALEOBOTANY

Plant fossils are classified into two groups: (1) macrofossils, which are the larger plant members, such as stems and leaves, usually detached and often fragmented; and (2) microfossils, which are the shells or resistant outer walls of minute plants, such as diatoms, or of pollen grains and spores. Fruits and seeds vary considerably in size and overlap each group.

For several reasons pollen and spores have a particular importance in present-day geological research in New Zealand. (1) Being produced in large numbers, readily dispersed, and highly resistant, they are more often preserved than macrofossils. (2) They occur in sediments of terrestrial origin where no marine fossils are available, often in sufficient numbers for a comparison to be made of the relative abundance of different types. (3) Since they are also deposited in coastal waters and may be found associated with marine organisms they help to “date” sedimentary rocks in relation to marine fossil sequences.

Evidence of Climatic Change

Much of the evidence of climatic change depends on the former occurrence of lowland trees north or south of their present limits, the number of degrees in latitude giving some indication of the magnitude of the climatic difference. Wood and resin, indistinguishable from that of the living kauri, occur in Tertiary lignites in Otago. These show that kauri forests once grew much further south than their present range, and indicate a warmer climate in the Tertiary. Kauri pollen occurs in South Island Upper Miocene to Pliocene deposits, and well-preserved leaves of Oligocene age have been found at Landslip Hill, so that the southern extension of the group to which the kauri belongs is shown by these different fossils – wood, resin, leaves, and pollen. Cone scales from Shag Point (Upper Cretaceous) and Mokoia and Waikawa (Jurassic) show also that the kauri family has had a long history in New Zealand.

Seasonal variation in climate may be shown by differences in growth rings. These are clearly shown in Upper Jurassic fossil woods from Waikawa, Curio Bay, and Waikato Heads. Coniferous wood, which seems to have predominated in the formation of the Tertiary lignites of the South Island, also shows growth rings. (The Tertiary fossil woods, as well as spores and leaf cuticles, are described by W. P. Evans in the N.Z. Journal of Science and Technology, Vol. 9–19, 1928–37.)

Apart from numerous, but small and mostly unclassifiable fragments of Mid-Devonian to Carboniferous age, Paleozoic plant life is represented in New Zealand by plant fossils from the Gore district. The fossils identified are of Permian age and link New Zealand with the supposed ancient southern continent, Gondwanaland, and in particular with Queensland through the occurrence there and in New Zealand of Cladophlebis roylei Arb. (a fern-like plant), Sphenopteris lobifolia Morris (seed-fern), and Neoggerathiopsis hislopii (Bunbury) (a cone-bearing plant).

Links With Modern Ferns

One of the oldest plant microfossils so far named from New Zealand deposits is Osmundacidites wellmani Couper. This Jurassic spore is considered to be related to the living family Osmundaceae, which is represented in New Zealand by three species of Todea. The apparent link between this ancient spore and the modern ferns is supported by other evidence. Fossil stems known as Osmunda dunlopi Kidston and Gwynne-Vaughan, from Waikawa and Kawhia (Jurassic) are evidently closely related. These are of interest on account of their anatomical similarity to modern forms, and they show the extreme slowness with which the family structure has been modified. According to Sinnott (Annals of Botany, 1914) “there is perhaps no other case among vascular plants where there has been so little change from Mesozoic time to the present”. This stability over a period of more than 135 million years is well exemplified by our living Todea barbara (L.) Moore, not only in stem anatomy but also in frond and spore type.

Cladophlebis australis (Morris) is presumed also to be the foliage of an osmundaceous fern. Hence there is a plausible linkage between micro - and macrofossils which has a bearing on the ancestry of certain present-day ferns. The history of the Osmundaceae in New Zealand is extended by the presence of Cladophlebis roylei among the Permian plant fossils mentioned above. Of similar antiquity is Cyathidites, a fern spore which may be ancestral to the modern tree-fern genus Cyathea, the spores of which are common in Quaternary deposits. The black tree fern Cyathea medullaris (Forst. f.) Swartz, the finest of our present-day tree-ferns, appears to be a comparative newcomer in this ancient lineage, since the spores have not been found in deposits older than Upper Miocene, though common in younger deposits.

Character of Earlier Forests

Branchlets from Cretaceous and Eocene beds in the South Island were identified as belonging to the genus Casuarina, which contains the modern sheoaks of Australia and Polynesia. Also believed to represent this genus, and first appearing in the Upper Cretaceous, is Triorites harrisii Couper, a pollen type which is common in most Tertiary assemblages, but became extinct with the onset of the Pleistocene glaciations. The presence of Casuarina suggests that a forest of more open type than today's dense rain forest was prevalent in the warmer epochs of the Tertiary. Important groups in New Zealand Tertiary vegetation were beeches, conifers, and casuarinas.

The oldest dated deposits with the remains of angiosperms (flowering plants with enclosed seeds) are the Mid-Cretaceous beds in the Clarence valley, near Coverham. The pollen grains are of an unspecialised type, but with the three furrows which distinguish them as dicotyledonous. Of the three more specialised pollen types of the southern beeches, two appear during the Cretaceous and the third in the early Tertiary. The first to appear, and the one which became dominant during the Tertiary, represents a section of the genus Nothofagus with living species in New Guinea and New Caledonia, but now extinct in New Zealand. Fossil Fagus (European beech) pollen has not been identified in New Zealand as yet and, as it is of an unspecialised type, confident identification is hardly to be expected. Thus the linkage of the southern beeches, genus Nothofagus, with the Northern Hemisphere beeches, genus Fagus, remains obscure. As a possible “missing link” may be mentioned the much discussed leaf fossils known as Artocarpidium arberi Laurent of Upper Cretaceous age from Pakawau. Oliver, in an unpublished manuscript, points out the resemblance of the venation to that of Fagus sylvatica and proposes a new genus for them, Protofagus. Oliver also suggests an affinity of the New Zealand leaf fossil Nothofagus ulmifolia Ett. (Cretaceous) with the South American beeches, in particular N. procera. Most of the fossil southern beeches had larger leaves than the living New Zealand species. The leaf fossil Nothofagus ninnisiana Unger from the Upper Cretaceous (Shag Point) and Lower Tertiary (Waikato and Ohai) is a broad-leaf type and fossil wood, believed to be that of large-leaved beeches, was described by Evans in the articles mentioned above. In the fossil record, as compared with the four or five species now living, 23 species have been named from macrofossils and 12 or 13 from microfossils, indicating the variety and importance of the southern beeches in the former vegetation of New Zealand and the closeness of present-day New Zealand to the centre of evolution and dispersal within this group.

Fruits and Seeds

Fossil fruits and seeds as yet yield a meagre record. At Coopers Beach, Mangonui, and at one or two other localities along the east coast, fossil coconuts of probable Miocene age have been found. These were named Cocos zealandica by Berry. The coconut fruits may have been brought by oceanic drift, but in favour of a more local origin are the facts that New Zealand may have consisted at the time of an archipelago of small islands, and that large palm fronds have been found at the same and other localities. Berry also referred to another fruit resembling that of a species of the Australian Hakea. Hakea-like pollen is known from the Eocene of New Zealand. Seeds are more commonly preserved in Quaternary sediments and may make a valuable contribution to our knowledge of the Quaternary history of the flora. In 1953 D. R. McQueen described an assemblage of fossil seeds from the Rangitikei Valley (Quaternary), of which 24 belonged to living species. A concise summary of the history of the flora of New Zealand was published by W. R. B. Oliver in a Swedish journal (Svensk Botanisk Tidskrift, 1955), and Oliver also contributed a similar article to Tuatara (1950). A useful work on the conditions under which the New Zealand flora evolved is New Zealand Biogeography, by C. A. Fleming, in Tuatara (1962). In the Transactions of the Royal Society of New Zealand, Vol. 83, there are papers by Shona Bell, H. J. Harrington and I. C. McKellar, and D. R. McQueen, and these give further useful references to the literature on New Zealand plant fossils. For plant micro-fossils the reader is referred to N.Z. Geological Survey Paleontological Bulletin 32 (1960), by R. A. Couper.

by William Francis Harris, D.SC., New Zealand Geological Survey, Department of Scientific and Industrial Research, Lower Hutt.