Tuatara: Volume 16, Issue 2, July 1968
A guide to New Zealand Recent Brachiopods
A guide to New Zealand Recent Brachiopods
Brachiopods are a declining group of marine organisms, today enjoying little of their former importance in benthonic communities of the continental shelf. With a long and rich fossil history behind them, they have dwindled in numbers through the Mesozoic and Cenozoic Eras until today they are rare or minor elements of the marine fauna. Since they are seldom seen in living communities, and since they are important neither as edible shell-fish nor as destructive pests, brachiopods have received little attention from marine zoologists and often go unrecognised by amateur collectors. However to paleontologists, such as this writer, the study of living brachiopods is essential to understanding the complex evolution of this interesting group.
New Zealand is an especially favoured place for studying living brachiopods because at least 12 species inhabit the surrounding seas. Of these, 3 can be collected intertidally and 4 others live in water shallow enough to be easily dredged. Only three of the 12 species, all type species of their genus, have been studied in some detailed biologically. The others, including 5 additional type species, are not well known, and much remains to be discovered about their distribution, ecology, anatomy, and life history.
The purpose of this paper is to focus more attention on the Recent brachiopods of New Zealand, and to make their identification casier. All 12 known species are described, 11 are illustrated, and the limits of present knowledge of their distribution are given. The need for new observations can readily be seen.
All brachiopods share some basic, common traits. They are solitary animals with a bivalve external shell, the values being located dorsally and ventrally, and each being bilaterally symmetrical from anterior to posterior. They are marine, benthonic, sessile, and nearly always epifaunal animals. Most are attached to the substrate by a pedicle which emerges from and is mainly attached to the longer of the two valves; hence that valve is called the pedicle valve. Most page 128 of the cavity between the valves is filled by a ciliated lophophore by which food particles are filtered from the water. In many species, the lophophore forms two elongate variously coiled extensions from either side of the mouth which are called brachia (see fig. 8); hence the valve which supports the lophophore is called the brachial valve.
In classifying brachiopods both shell and anatomical features are used. However, the shell characters are of the greater importance because they can be recognised not only in the several hundred living species but also in the 40,000 or more known only as fossils. The long range evolutionary significance of shell characters can be evaluated. In particular, the microscopic structure of the shell, the internal structures of the brachial value which give support to the lophophore, and the modifications of the opening through which the pedicle emerges are of major importance in defining orders, families and genera.
The three orders represented by New Zealand species can be distinguished by differences in their shell structure. The shells of all Terebratulida, the order of which most New Zealand Tertiary and Recent brachiopods belong, are penetrated by small, unbranched pores, the punctae, about 150 per square millimeter, containing microscopic extensions of the mantle. These can be seen with the aid of a 10 power magnifier. In contrast, none of the Recent or Tertiary Rhynchonellida are punctuate. Among the inarticulate brachiopods, some, such as the Craniidae, are punctuate; but their punctae are irregular, branching, and not hcmologous with those of the Terebratulida. These differences can be seen in cross sections of the shell magnified by 10 or more times.
Characters which have been used to define the genera listed below include structural variations in the cardinalia (structures at the posterior of the brachial valve including the lophophore supports; for example, see figs. 3C and 8F) and the foramen (for example, figs. 2A, 3F, 4A and 5A), and differences in the nature of the external ornamentation.
Species have been based on differences in shape and on trivial but consistent variations in the other characters. Each of the New Zealand species exhibits intraspecific variation in shape and ornamentation; thus an adequate sample is needed so that end members of a series are not mistakenly identified as distinct species. In addition, non-genetic variation, usually resulting in asymmetry, caused by injury, disease or confinement between rocks or other shells is common, especially in Notosaria nigricans, and Magasella sanguinea.
The internal characters and, if possible, a developmental series of specimens should be examined in identifying New Zealand Terebratulida in order to separate homeomorphs, animals that look alike but are not closely related. An example of homeomorphy is illustrated by the specimens of Liothyrella neozelanica and Neothyris page 129 lenticularis shown in figures 3A and 11A. Although the external resemblance is striking, the two shells belong to different suborders, each with a long and independent paleontologic history extending from the Triassic Period, more than 200 million years ago. The important character by which they can be distinguished is the calcareous loop which supports the lophophore. It is morphologically and ontogenetically different in the two suborders. In the Terebratellidae, the loop, (fig. 11D) is long and grows from both the cardinalia and the median septum during ontogeny, but may be free of the septum at maturity; whereas the loop of the Terebratulidina (figure 3C) is short, grows from the cardinalia only, and is never attached to the median septum.
References are given in the text by number only, with full citations listed numerically at the end. The classifications and terminology used follow that proposed by Williams and others (1). Data on the distribution of brachiopod species where not followed by references are from my own unpublished observations and from examination of collections made by the New Zealand Oceanographic Institute.
In the text, the dimensions given for shell size are: total anterior to posterior length (abbreviated L), width (W) measured perpendicular to the plane of symmetry, and thickness (T) measured perpendicular to the length and width. An asterisk (*) following a species name indicates that it is the type species of the genus. Average values for density of punctation are listed, but they are quite variable from shell to shell and even from place to place on a single shell, sometimes by as much as + or — 25 punctae per square millimeter. Until it has been studied systematically, density of punctation is not a reliable character for identifying the different species.
All figures are natural size except where noted. The convential orientation of the shells with the beak or the brachial valve at the top of the page is followed.
Adductor Muscles (labelled a, fig. 8 — muscles which contract to close the valves.
Amphithyridid Foramen (af, fig. 4) — pedicle opening formed by the triangular delthyrium of the pedicle valve and a semicircular notch in the brachial valve.
Apical Plate (ap. fig. 2) — partial sheath for pedicle in apex of delthyrium.
Ascending Branches of Loop (as, fig. 6) — recurved portion of loop nearest to the pedicle valve.page 130
Beak (b, fig. 2) — posterior end of pedicle valve, usually penetrated by the foramen. Beak is erect if it points towards the brachial valve perpendicular to the commissure; incurved if it points more anteriorly.
Brachial Valve — smaller of the two valves to which the lophophore supports are attached.
Capillate — ornamented by very fine radial ribs.
Cardinalia — internal shell structures at the posterior of the branchial valve.
Cardinal Process — an elevated stucture at the posterior of the brachial valve which either separates the diductor muscles (cp, fig. 11) or serves as a site of attachment for them (ds, figs. 3 and 8).
Commissure (co, fig. 2) — surface of contact between the two valves.
Crura (cr, fig. 2) — rod - like structures which support the posterior part of the lophophore. The crura continue into the descending branches of the terebratellid loop. (Singular — crus).
Crural Process (c, fig. 3) — a medially directed point on each crus.
Delthyrium (del, fig. 4) — triangular opening at the posterior of the pedicle valve which may be partially or completely closed by deltidial plates. When no plates are present, the entire delthyrium serves as the foramen.
Dental Plates — a pair of plates in the pedicle valve which buttress the hinge teeth.
Dental Sockets (soc, fig. 2) — a pair of depressions at the posterior of the brachial valve into which the hingle teeth fit.
Descending Branches of Loop (de, fig. 6) — portion of the loop connected to the cardinalia and passing nearest to the bottom of the brachial valve.
Diductor Muscle (di, fig. 8) — used to open the valves.
Epithyridid Foramen (ef, fig. 3) — foramen in the pedicle beak not impinging on the delthyrium.
Hinge Plates — plates in the posterior of the brachial valve subparallel to the commissure on which pedicle adjustor muscle page 131 may be seated. Outer hinge plates (oh, figs. 2 and 3) join the socket walls to the crural bases. Inner hingle plates (ih, fig. 6) joins the crural bases across the midline.
Holoperipheral Growth (hgl, fig. 1) — growth along valve periphery in all directions from the apex.
Hypothyridid Foramen (hf, fig. 2) — pedicle opening confined to the delthyrium, not impinging on the beak.
Loop (l. fig. 3) — calcareous structure supporting the lophophore with bands extending from each crus joined to form a closed ring.
Magadiniform Loop — descending branches and ring-like ascending branches independently connected to median septum but not to each other.
Magellaniiform Loop (fig. 11) — long, recurved loop not connected to median septum.
Magelliform Loop — similar to magadiniform loop but with descending and ascending branchese connected to septum in one fused point.
Median Septum (s, fig. 5) — blade-like elevation along the midline of either valve.
Mesothyridid Foramen (mf, fig 9) — pedicle opening partially in the delthyrium and partially through the beak.
Multicostellae (mu, fig. 2) — radial ribs of more or less equal size.
Pedicle — organ by which brachiopod attaches to substrate.
Pedicle Collar — a ring-like sheath of shell material surrounding the pedicle and projecting inward from the foramen.
Pedicle Valve — longer of the two valves, bearing the hinge teeth and through which the pedicle emerges.
Pre-Magadiniform Loop — descending branches grow from both septum and cardinalia but do not meet; ascending branches forming small ring on septum.page 132
Punctae — numerous, small blindly ending perforations of the shell bearing extensions of the mantle.
Socket Ridge (sr, fig. 4) — ridge forming the inner socket wall.
Spicules — small, irregular calcareous plates secreted in the body for support.
Submesothyridid Foramen — pedicle opening mainly in the delthyrium but impinging on the beak.
Sulciplicate — fold in the brachial valve bearing a smaller median sulcus.
Sulcus (su, fig. 5) — a median depression on either valve. The corresponding elevation on the other valve is the fold.
Symphytium (sy, fig. 3) — a single plate closing the delthyrium.
Terebratuliform Loop (fig. 3) — short loop with descending branches and transverse band only. Develops from cardinalia only.
Transverse Band (t, fig. 6) — band joining the posterior ends of the ascending branches.
Uniplicate (fig. 2) — shells bearing a fold on the brachial valve and a sulcus on the pedicle valve.
Zygolophous Lophophore — consisting of a pair of curved brachia.
Key to the Genera
|Valves not articulated by hinge teeth and sockets||Crania|
|I. Shell impunctate||Notosaria|
|II. Shell punctuate.|
|A. Lophophore supported by short, terebratuliform loop||Liothyrella|
|B. Lophophore not supported by calcereous structures, shell very small.|
|1. Foramen amphithyridid||Amphithyris|
|2. Foramen submesothyridid, deltidial plates disjunct||Pumilus|
|C. Lophophore supported by long, recurved calcareous loop.|
|1. Cardinalia not massive, cardinal process small.||page 133|
|a. Shells with radial ribs from beak to anterior, conjunct deltidial plates.|
|Cardinalia thin and delicate||Magasella|
|b. Shells smooth or with very weak ribs at the anterior, deltidial plates disjunct.|
|2. Cardinalia massive, cardinal process larger||Neothyris|
Valves not articulated by hinge teeth or dental sockets. Lophophore not supported by outgrowths of the shell. Alimentary canal with terminal anus.
Outline sub-circular, growth commonly holoperipheral in one or both valves. Shell either calcareous and punctate or phosphatic. Pedicle absent, or if present pedicle opening confined to pedicle valve.
Shell calcareous and punctate, pedicle absent, Valves subconical; growth holoperipheral.
Attached by cementation of pedicle valve to rocks or shells. Ornamented by concentric growth lines, and in a few species by radial ribs. Valve margins thickened, the inner edges are flattened and usually granulated.
Crania huttoni (2)
(3): High Island off Taurikura Bay, Whangarei Heads on rocks near low tide (4); Poor Knights Island; 6-7 fathoms: Three Kings Islands, 440 fathoms (3), and 140 fathoms.
Few specimens of this species have been found so far; but since they closely resemble common limpets, they are likely to be overlooked by all but the expert. They can be distinguished from limpets by their distinctive paired muscles. Of the specimens I have examined, only the holotype bears radial ribbing. It is either absent or not preserved on the others.
Valves articulated by hinge teeth and dental sockets. Shell calcareous, punctate or impunctate. Lophophore commonly with some calcareous support. Alimentary canal ends blindly, no anus.
Shell impunctate (with rare exceptions among Paleozoic fossils). Beak pointed, delthyrium modified by deltidial plates. Pedicle functional. Lophophore partially supported by crura only. Lophophore spirolophous with cone axes nearly perpendicular to the plane of commissure. Two pairs of metanephridia present. (Other groups have only one pair).
Shell impunctate. Lophophore supported by short, bluntly pointed crura which arise from the ventral side of the small outer hinge plates and curve so as to project into the other valve.
Shell multicostellate from beak to margin. Growth lines prominent anteriorly, but not lamellose and not developed into spines. Commissure uniplicate. Foramen large, hypothyridid. Deltidial plates disjunct. Median septum in brachial valve low and not extending to the apex. Cardinal process small.
Notosaria nigricans* (5)
Colour black to dark bluish grey. Outline transversely oval. Beak prominent, pointed; deltidial plates and apical plate clearly visible. Multicostellae prominent, 20 to 30 on shells 2 cm in length. Two to six multicostellae occupy the sulcus. Dimensions of a typical shell: L 21, W 24, T 11 mm.
Figure 2: Notosaria nigricans. A, B, C, D. Brachial, side, anterior, posterior views. E. Brachial interior with spirolophous lophophore, filaments exaggerated in thickness. X2. F, G. Brachial and pedicle interior views.
ap—apical plate, b—beak, co—commissure, cr—crus (pl. crura), d—disjunct deltidial plates, dg — digestive gland, hf — hypothyridid foramen, ht — hinge tooth, i — intestine (no anus), lo — lophophore, m — mouth, mu — multicostellae, oh — outer hinge plate, soc — dental socket, st — stomach.
Distribution: Milford Sound (6); around Stewart Island; Foveaux Strait north to Lyttelton Harbour (7, 8); Queen Charlotte Sound (9); off Stephens Island, Cook Strait (3); near Nelson (3); Wellington Harbour (3); Palliser Bay; Great Barrier Island (10); around Chatham Islands; low tide to 100 fathoms, and found rarely in deeper water.
This species is easily distinguished by its sharp radial ribs and dark grey colour. Although empty shells are commonly washed ashore along the east coast of the South Island, they are difficult to collect alive. They are known intertidally from one locality in Lyttleton Harbour. In other areas they are sometimes found in the holdfast of Macrocystis.
A ‘variety’ of this species, pyxidata (11), was named for specimens taken south of Kerguelen Island in 150 fathoms. They were distinguished from N. nigricans by finer multiplication, 40 to 46 on each valve, and white to brownish colour (12). It is likely that N. nigricans will be found at other favourable sites between Great Barrier Island and the Kerguelens.
Shell punctate; beak rounded, not pointed. Foramen large and circular in most; delthyrium modified by deltidial plates. Lophophore supported by a calcareous loop which develops either from the cardinalia alone or from both the cardinalia and the median septum. Loop secondarily lost or reduced in some groups.
Loop short, developing from cardinalia only. Medium septum usually absent.
Cenozoic and most Mesozoic terebratulidina. Brachial median septum and dental plates rarely developed. Outer hinge plates and small cardinal process usually present; inner hinge plates present in some families.
Loop terebratuliform; crural processes not united to form ring-like loop. Outer hinge plates present; inner hinge plates present in some genera. Brachial median septum and dental plates absent. Shell lacking strong radial ornament; some capillate. Lophophore plectolophous. Spicules present.
Shell smooth or finely capillate; strongly biconvex; commissure uniplicate. Foramen large, epithyridid; pedicle collar developed. Pedicle exits in a postero-dorsal direction. Delthyrium closed by a small concave symphytium which is not impinged upon by the foramen. Loop quite short, and somewhat triangular. No inner hinge plates. (This genus may prove to be a junior synonym of Gryphus).
Figure 3: Liothyrella neozelonica. A, B, C. Brachial, side and brachial interior views of a larger specimen with an unusually small foramen. X0.7. D, E, F, G. Brachial side, posterior, and anterior views of a typical small shell. X0.7.
c — crural process, ds — diductor muscle seat, ef — epithyridid foramen, gl — growth lines, l — loop (terebratuliform), oh — outer hinge plate, si — pallial sinus where filled with eggs, sy — symphitiam.
Liothyrella neozelanica (13)
Shell large, elongately oval, strong biconvex. Surface ornamented by prominent growth lines and very subdued radial capillae. Beak truncated by a large epithyridid foramen. Spicules well developed. Density of punctation: approximately 175 per square millimeter.
Distribution: Three Kings Islands, 440 fathoms (3); Cook Strait, 50 to 150 fathors (3, 13, 14); Tasman Bay, 45 to 55 fathoms (3); off Kaikoura, 70 fathoms; Pegasus Bay; Chatham Rise, 100 to 200 fathoms; Fiordland, 15 to 40 fathoms (7); entrance to Milford Sound, 20 fathoms (3); off Karamea, 45 fathoms.
This brachiopod can be distinguished from the others by its whitish colour and by its large, round foramen which can be seen easily from the posterior. This handsome animal grows to a large size for brachiopods, and although only a few have been found in water shallower than 50 fathoms, it is well adapted to life in shallow turbulent water with a thick shell and a stout pedicle.
Liothyrella sp (15)
A single specimen taken from Foveaux Strait was described and figured by Thomson. The specimen, small, subcircular in outline and with a Liothyrella-like loop, was considered to be a juvenile and not named. However, because of differences in the spiculation, Thomson (13) later regarded this species as distinct from L. neozelanica. More specimens are needed before the Foveaux Strait species can be identified properly.
Loop long, developing during ontogeny from both the cardinalia and the median septum, but may be free of septum at maturity.
Cenozoic and some Mesozoic terebratellidines.
Plano-convex shells with an amphithyridid foramen. Loop absent or with descending and ascending branches separately attached to septum. Spicules present.
Outline subcircular with wide hinge line. Pedicle passes through a large amphithyridid foramen. No loop present. Lophophore schizolophous. Cardinalia consist of socket ridges only.
Amphithyris buckmani* (13)
Shell small, up to 5 mm in diameter. Surface smooth except for growth lines. Surface of the pedicle valve reported to be ornamented with fine, raised, radial lines, but these were not seen on several score of small specimens borrowed from the Dominion Museum. Density of punctation: approximately 160 per square millimeter.
Distribution: Cook Strait near Wellington; 120 fathoms.
This is a very small, easily overlooked brachiopod. The distinctive foramen, in part notched from the brachial valve, readily separates it from the other New Zealand brachiopods. It undoubtedly has a wider distribution than we presently know. It should be looked for attached to rocks and other shells, and may be found in large numbers.
Lophophore zygolophous to plectolophous. Loop absent, or with descending branches attached to ring formed by ascending branches on median septum. Spicules present. Dental plates absent.
Schizolophous lophophore. No loop or cardinal process.
Pumilus antiquatus* (16)
Shell small, less than 5 mm in length, longer than width. Growth lines prominent, commissure distinctly sulcate. Deltidial plates very narrow, foramen submesothyridid. Apical plate well developed. Density of punctation: approximately 280 per square millimeter.
Distribution: Near low tide at Lyttleton (16, 23) and Otago Harbours, shallow water off Warrington (17).
This is another very small brachiopod, easily overlooked in the hasty sorting of a dredge haul or in the examination of rocks in shallow water. For many years it was mistaken for the young of Waltonia inconspicua with which it occurs. Its dark grey to white colour and pronounced fold and sulcus distinguish it from small W. inconspicua. It lives under rocks in sheltered, rocky, shallow water areas hidden from light and protected from strong waves. It is also found in the holdfasts of Macrocystis with Notosaria nigricans and Waltonia inconspicua.
This species was first recognised only ten years ago, and little is known yet of its distribution. It will undoubtedly be found to be more widespread as more people learn to recognise it.
Loop passes through all or part of the developmental series — pre-magadiniform, magadiniform, magelliform, terebratelliform and magellaniiform — during ontogeny. Pedicle valve lacks dental plates. Spicules absent.
Cardinalia not thickened by massive, callous deposits; cavities formed beneath inner hinge plants on either side of the unbifurcated median septum. Deltidial plates disjunct to conjunct. Foramen large, directed posterodorsally. Loop magelliform to magellaniiform in adult. Lophophore plectolophous.
Shell multicostate. Deltidial plates conjunct. Foramen large, circular, mesothyridid. Loop terebratelliform.
Magasella sanguinea* (18)
Colour reddish pink. Shell large, length slightly greater than width. A large shell from Patterson Inlet measures: L 37, W 35, T 24 mm. Multi costae prominant, some bifurcate, 45 to 60 present on large shells, 6 to 12 occupy the brachial sulcus. Beak nearly erect. Density of punctation: average 200 per square millimeter; count higher between than on multi costae.
Distribution: Around Stewart Island; Foveaux Strait north along the east coast to Cook Strait, Queen Charlotte Sound, Pelorus Sound (?), and Wellington Harbour, 10 to 150 fathors (3, 7, 9 23); Doubtful Sound, 2 to 3 fathoms (19, 23).
This is the most common brachiopod on the Otago Shelf where it is widespread and can usually be taken with an Agassis trawl in 40 to 50 fathoms among abundant and varied calcareous bryozoans. However, it is not abundant and specimens typically number fewer than a dozen in a cubic yard of bottom sample.
In Foveaux Strait large specimens of M. sanguinea are commonly taken in the oyster dredges. In nearby Patterson Inlet they are locally abundant and of large size in waters less than 10 fathoms deep.page 142
Figure 6: Magasella sanguinea. A, B. Brachial and side views. C. Pedicle interior. D. Brachial interior showing terebratelliform loop.
as — ascending branch, cb — connecting band, cd — conjunct deltidial plates, de — descending branch, ih — inner hinge plate, mf — mesothyridid foramen, si — pallial sinus where filled with eggs, t — transverse band.
Because this species usually lives at depths greater than 10 fathoms, it is not often washed up onto New Zealand's shores. A complete shell with the delicate, ribbon-like loop intact is a rare and treasured find for the shell collector.
Magasella haurakiensis (20)
Distinguished from M. sanguinea by weakly developed multicostation, elongately oval outline, suberect beak, and pale pink colour. Density of punctation: approximately 160 per square millimeter. Dimensions of holotype: L 34, W 28, 20 mm.
The difference between this species and M. sanguinea is very small, and it is likely that M. haurakiensis is nothing more than a geographic variant of M. sanguinea. More samples collected from the southern waters of the North Island will probably show that they grade into each other.
Surface multicostate. Beak suberect to incurved. Deltidial plates conjunct, foramen round, mesothyridid, relatively large. Cardinalia and hinge teeth bases somewhat thickened, but not massively as in the Neothyridinae. Loop terebratelliform.
Gyrothyris mawsoni* (13)
Elongately suboval; dimensions of a large specimen: L 26, W 24, T 14 mm. Multicostellae vary from weakly to strongly developed. Growth lines prominent near commissure. Commissure sulcate. Colour dark grey to colourless.
Distribution: Around Macquarie Island and Antipodes.page 144
Figure 8: Gyrothyris mawsoni. A, B, C. Brachial side, and anterior views. D. Pedicle interior showing complete pallial sinuses; portions used for egg storage are stippled. E. Brachial interior showing plectolophous lophophore; filaments exaggerated in thickness. F. Brachial interior with complete terebratelliform loop. D, E, F. X2.
a — adductor muscle scar, aj — pendicle adjustor muscle scar, di — diductor muscle scar, lo — lophophore, si — pallial sinus.
The Macquarie Island specimens of this species resemble Magasella sanguinea but lack its characteristic reddish colour. On the inside, the shell structures are more thickened than in M. sanguinea.
Shell smooth or with weakly developed multicostation anteriorly. Deltidial plates disjunct. Foramen large, mesothyridid. Loop terebratelliform.
Waltonia inconspicua* (5)
Colour red to pink. Shells small to medium size, length usually a little greater than width. A large specimen from Otago Harbour measures L 17, W 16, T 9 mm. Commissure sulcate. Density of punctation: approximately 170 per square millimeter.
Distribution: Stewart Island to Great Barrier Island, Mangonui and Wheangarei Heads, from mid-tide to over 100 fathoms (3, 7, 21, 23). Best known from near low tide at Otago, Lyttelton and Auckland Harbours. Cook Strait off Stephens Island, 110 fathoms (3); Palliser Bay, 13 fathoms; Doubtful Sound, 2 to 3 fathoms (19, 23); Dusky Sound, 12 to 15 fathoms (3); around Auckland Islands and Chatham Islands.
Figure 9: Waltonia inconspicua. A, B, C. Brachial, posterior and anterior views of a large shell. D, E, F. Brachial and side views. G. Brachial interior with complete terebratelliform loop. H. Pedicle interior. I. Brachial interior with plectolophous lophophore; filaments exaggerated in thickness. X2.
aj — pedicle adjustor muscle scar, d — disjunct deltidial plates, mf — mesothyridid foramen.
Shell smooth except for growth lines. Deltidial plates disjunct; foramen mesothyridid. Cardinal process of moderate size and transverse. Loop magellaniiform.
Aerothyris macquariensis* (13)
Shell medium to large size, elongately oval. A large shell dredged off Otago measures: L38, W 30, T 20 mm. Foramen large, mesothyridid; beak nearly erect. Commissure sulcate. Density of punctation: approximately 120 per square millimeter.
Distribution: Around Macquarie Island, and Antipodes, 40 to 100 fathoms; and empty shells off Otago Peninsula, 180 to 220 fathoms.
Externally, this brachiopod is similar to W. inconspicua, however it is usually larger and the internal shell structures are quite different. A. macquariensis has a magellaniiform loop and a large cardinal process.
Cardinalia massive; hinge plates, socket walls, crural bases, and septum much thickened in adults; no cavities beneath hinge plates. Median septum bifurcates to form a hinge trough. Loop magadiniform to magellaniiform.
Surface smooth except for growth lines. Foramen small for shell size, mesothyridid; deltidial plates conjunct. Internal structures swollen; cardinal process stout and nearly filling hinge trough. Loop magellaniiform. Lophophore plectophous.
Neothyris lenticularis* (22)
Colour dark to light pink. Shells large, often greater than 4 cm long, length slightly greater than width. Outline nearly circular in shells up to about 2 cm in length, but length and thickness increase at greater rates in larger shells. Greatest width anterior to mid length in large shells. Beak markedly incurved; foramen quite small; pedicle not functional in large animals. Cardinal process large with a central lobe which fits between the diductor muscles. Median septum extends nearly to mid length.
Distribution: Around Stewart Island; Dusky Sound, 12 to 15 fathoms (3); Foveaux Strait, 35 to 150 fathoms (13, 3); off East Cape, 85 fathors; off Mayor Island, Bay of Plenty, 40-110 fathoms (broken specimens) (3); Chatham Rise, 100 to 150 fathoms; near Antipodes Island, 82 fathoms; Campbell Plateau, 62 fathoms; around Campbell Island 103 fathoms; and near Auckland Island, 52 fathoms.
Figure 11: Neothyris lenticularis. A, B, C. Brachial, side, and anterior views. D. Brachial interior with complete magellaniiform loop. E. Pedicle interior. cp—cardinal process, ds—ciduclor muscle seat, htr—hinge trough.
Although all of the specimens examined by me in this study were identified as Neothyris lenticularis, more than one species of the genus may be present in this region. Some geographic variations exists between specimens from the Chatham Islands, Cook Strait, Foveaux Strait and the southern islands. The shells collected in great numbers on the Chatham Rise, near the Chatham Islands, by the New Zealand Oceanographic Institute appear to be consistently more elongate and smaller than the typical N. lenticularis from Foxeaux Strait. Shells of comparable size from Foveaux Strait are nearly circular in outline, while the Chatham Island specimens are elongately ovate. In the Cook Strait area, rare shells washed up on Farewell Spit differ from the typical N. lenticularis in having a larger foramen and a beak that is not incurved. In these animals, the pedicle must have remained functional throughout its lifetime, a contrast with the Foveaux Strait specimens. Shells from Farewell Spit were identified by Thomson (15) as A. ovalis (Hutton), a fossil species. In the subantarctic island region south of New Zealand, specimens of Neothyris reach a large size not attained to the north.
To determine whether more than one species is present requires a detailed study of all the Neothyris populations from this region coupled with a study of the abundant Tertiary fossil representatives of the genus on both the North and South Islands and the Chatham Islands. Such a study is not within the scope of this paper.
I wish to thank Dr E. J. Batham of the Portobello Marine Biological Station for use of the station's facilities including the R.V. “Munida”, and for her suggestions on this manuscript. I also thank J. W. Brodie and E. W. Dawson for allowing me to examine the N.Z. Oceanographic Institute's brachiopod collection, and Dr. R. K. Dell and W. F. Ponder, of the Dominion Museum, for the loan of a number of type specimens and for information on the distribution of some of the species. I also thank J. Graham, of Oamaru, for letting me examine his brachiopod collection from the North Otago shelf and borrow several specimens, Professor J. E. Morton of the University of Auckland for information about Crania huttoni, J. A. Grant-Mackie of the University of Auckland and Dr. A. W. B. Powell of the Auckland Museum for allowing me to examine the brachiopod collections in their care.
To J. D. Campbell of the University of Otago I owe a special thanks for his very willing help and advice in the preparation of this paper.
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* type species of genus.