New Records of the Genus Lingula (Brachiopoda) from Tertiary Strata in New Zealand
[Read before the Philosophical Institute of Canterbury, May 1, 1935; received by the Editor, May 30, 1935; issued separately, March, 1936.]
The genus Lingula is not a constituent of the Recent fauna of New Zealand. It is confined to the warmer waters of the Indian Ocean and the western Pacific margin from Queensland to Japan. As J. A. Thomson (1927, p. 127) has noted, the present restriction has only been effected in a geologically late period. Lingula occurs in the Tertiary (“Miocene”) of Seymour Island, Antarctica (Buckman, 1910, p. 9, pl. 1, fig. 7), and ranges from the Eocene to the Pliocene in Europe. Thomson (1927, p. 127) suggested that further species might “be expected from the Oligocene-Miocene rocks of South America, the Antarctic, Australia, or New Zealand, which were deposited during a period of warm climate.”
As far as the New Zealand area is concerned, Thomson's prediction was justified, for in 1930 W. H. A. Penseler described Lingula waikatoensis from claystones overlying coal measures at the Renown Colliery, Waikokowai, Waikato District.
Through the courtesy of Professor W. N. Benson, of Otago University, and of Dr. H. J. Finlay, the writer in now able to add three new records of this genus from New Zealand Tertiary strata. Unfortunately, in all three cases the material available is fragmentary, and it has not been possible to carry out any descriptive or comparative work. However, the genus is so rare in New Zealand that a record of the new occurrences might serve to stimulate renewed activity on the part of collectors at the localities concerned.
Description of Material.
(a) Green Vale, Shag Valley.
In the collection of brachiopods formerly in the Otago Museum, but now transferred to the Department of Geology, Otago University, is a tray containing five fragments of a Lingula from an unknown horizon, presumably of Tertiary age, at Green Vale, Shag Valley. The specimens were collected by Miss Janet Moller in 1908. The exterior of the valves is a pale-cream colour, and is highly polished. The interior of the largest fragment, the posterior half of a ventral valve, is perfectly preserved. If one may judge by the number of specimens, and their preservation, further search in this locality would yield interesting material.
(b) Clifden, Southland.
Dr. H. J. Finlay found a single broken valve of a Lingula in sieving matrix from Band 7 at Clifden. This horizon yields an interesting faunule of brachiopods, including such species as Neothyris
novara (von Ihering) and Stethothyris sufflata (Tate). Lingula is apparently very rare, and has not been found in other localities, such as Weka Pass or Takaka, where the sufflata fauna is well developed.
(c) Boulder Hill, near Dunedin.
Professor W. N. Benson collected three fragmentary specimens of a small species of Lingula at Boulder Hill, near Dunedin, from an horizon which yielded to Mr H. E. Fyfe and the writer a large and very interesting mollusean fauna of Wangaloan age. The Wangaloan stage is possibly the equivalent of the European Palaeocene; at any rate it contains the earliest Tertiary fauna known in New Zealand. This Lingula is the only known brachiopod at this horizon, and is the earliest known representative of the class in the Tertiary beds of the Dominion.
The largest fragment is three millimetres in greatest breadth, but the length cannot be determined, since the anterior margin is broken. The earliest growth-lines are sub-circular in shape, then change to broadly ovate, and at two millimetres the shape is elliptical; at three to four millimetres there is a slight narrowing of the front. Buckman (1910) has demonstrated that a study of the life-history as shown by the contour of the successive growth-lines is of value in comparative studies of the Lingulidae, where possible variation is so limited. In the case of the Boulder Hill species the ontogeny shows clearly that it is distinct from Lingula waikatoensis Penseler. The shape of the shell is not unlike that of the young form of L. waikatoensis (Penseler, 1930, text-fig. 9 on p. 445), but the earlier growth-lines are sub-circular to broadly ovate, and not narrowly ovate as in the Waikato form.
It is to be hoped that renewed search at Boulder Hill will result in the finding of complete specimens of this interesting shell.
Lingula as a Paleic Indicator.
Both plants and animals show direct responses to physical conditions, and therefore serve as indicators of them. This fact has been realised in a general way by palaeontologists, but the study and nature of indicators have been developed almost wholly with reference to plants. The principles underlying the indicator concept have been elucidated by F. E. Clements (1920), whose comprehensive and scholarly work contains a wealth of data of interest to the student of the ecology of fossil assemblages.
Clements makes a distinction between “factor-indicators” such as light-, temperature- or altitude-indicators, and “process-indicators” or the indicators of primary processes which cause or modify a particular factor. His work also includes a stimulating section on what he terms “paleic indicators” or the indicators which are significant in palae-ecology. He writes “The significance of paleic indicators rests upon the conviction that ecological processes were essentially the same during the geological past as they are to-day” (1920, p. 99); and “The control of the direct factors, water, light, temperature, etc., must have been just as to-day, and this is equally true of their modification by physiographic processes
and climatic changes, as well as by the competition and reaction of plant communities” (1920, p. 99). What Clements says of plants applies, with the necessary modification, to animals, marine or terrestrial.
Clements stresses the point that paleic indicators show one essential difference from other types, and that this difference “lies in the fact that communities were but rarely fossilized, and that the community itself must be inferred often from the merest fragments of its total population” (1920, p. 100).
Although established by plant studies, the general principle put forward by Clements applies equally well to the problems of zoo-ecology and palae-ecology. Its application to certain bio-stratigraphical problems promises to be most fruitful, and will yield results of great interest and importance.
As Penseler (1930) has shown, Lingula is a paleic indicator of some value. First, it is a climate-indicator, since at present the genus is confined to tropical and warm-temperate seas; second, it is a habitat-indicator, since Recent Lingulids are characteristic of, or dominants in, the shallow water (0—10 fathoms) of estuarine bays and deltas on sandy or muddy bottoms. In the case described by Penseler the climatic indication cannot be checked by other data, but the habitat indication is supported by stratigraphical position and by the associated fossils, which include “Cardium (small), Tellina, Dosinia, and a small gastropod resembling Cylichna or Bullinella” (Penseler, 1930, p. 447).
The writer has pleasure in recording his thanks to Professor Benson and Dr. Finlay for allowing him to study the fossils which this note records.
Buckman, S. S., 1910. Antarctic Fossil Brachiopoda collected by the Swedish South Polar Expedition, Wissensch. Ergebn. Schwed. Sudpolar-Exped., 1901–1903, Bd. 3, Lief. 7, pp. 1–43, pls. 1–3.
Clements, F. E., 1920. Plant Indicators: The Relation of Plant Communities to Process and Practice, Carnegie Inst. Washington, Pub. No. 290, xvi + 388 pp., 92 pls.
Penseler, W. H. A., 1930. A. Lingulid from the Tertiary Rocks of the Waikato District, Trans. N.Z. Inst., vol. 61, pts. 3, 4, pp. 441–451, pl. 68.
Thomson, J. A., 1927. Brachiopod Morphology and Genera (Recent and Tertiary), N.Z. Board Sci. and Art, Man. No. 7, vi + 388 pp., 2 pls.