Biodiversity of shallow-water brachiopods from New Caledonia, SW Pacific, with description of a new species

SUMMARY: Twelve species of recent brachiopods belonging to the genera Lingula , Discradisca , Novocrania , Xenobro- chus , Eucalathis , Frenulina , Argyrotheca , Campages , Thecidellina and Lacazella were identified in samples collected during shallow-water cruises around New Caledonia, southwest Pacific. Six genera, Lingula , Xenobrochus , Eucalathis , Frenulina , Campages and Thecidellina, have been already reported from the New Caledonian region, while four genera, Discradisca , Novocrania , Argyrotheca and Lacazella are the first records from this region. Additionally, Discradisca stella is the first discinid brachiopod recognized in the New Caledonia area. One new species is described, the megathyridid Argyrotheca neocaledonensis n. sp. The biogeographical affinities of the New Caledonia brachiopod faunas are briefly discussed. Cam- pages y Thecidellina) ya han sido registrados en la región de Nueva Caledonia mientras que cuatro de ellos ( Discradisca, Novocrania, Argyrotheca y Lacazella ) son registrados por primera vez en esta región. Además, Discradisca stella es el pri- mer braquiópodo discínido reconocido en el área de Nueva Caledonia. Una de las especies descritas es nueva, Argyrotheca neocaledonensis n. sp., de la familia Megathyrididae. También se discuten las afinidades biogeográficas de la fauna de estos braquiópodos de Nueva Caledonia. Palabras clave: braquiópodos recientes, biogeografía, aguas someras, Nueva Caledonia, taxonomía, nueva especie. present finding from off New Caledonia extends the biogeographical range of this species southwards. This is the first record of a discinid from New Caledonia.


INTRODUCTION
The New Caledonia exclusive economic zone (EEZ), situated between Australia and the Vanuatu archipelago, has one of the most intensively studied faunas in the southwest Pacific.Brachiopods from this region have mostly been collected from waters at more than 100 m depth (d'Hond, 1987;Laurin, 1992Laurin, , 1997;;Bitner et al., 2008b;Bitner, 2009) and until now only four species-two lingulides Lingula anatina Lamarck and L. adamsi Dall, a terebratulide Frenulina sangui-nolenta (Gmelin) and a thecideide Thecidellina maxilla (Hedley)-have been reported from waters shallower than 100 m (Emig, 1988;Bitner 2007a).
Between 1984 and 1989, within the French project "Lagon" 13 cruises were carried out in shallow waters around the largest island of New Caledonia, Grande Terre and around the Chesterfield atoll (Richer de Forges, 1991).The aim of this project was a large-scale geomorphological, sedimentological and faunistic study of each lagoon.The area of the study comprised 23400 km 2 and was systematically dredged; 1217 sam-ples were collected, mostly from depths between 5 and 100 m.Brachiopods were found at only 13 stations on the following five cruises-no.6 in November 1984, no. 10 in August 1986, no. 11 in January 1987, no. 12 in April-May 1988, and no. 13 in October-November 1989-carried out in the lagoon of the north, east and south coasts of New Caledonia (Fig. 1; see also Table 1).Only two stations contained more than one species, and only at station 830 were brachiopods rich in both specimens and species.The brachiopods are represented by either micromorphic or immature forms and all the material, except Lingula anatina, is clearly part of a death assemblage; some shells were filled with sediment.
In this report 12 species, including one new form, are described.The most interesting finds are the first records of the genera Discradisca, Novocrania, Argyrotheca, and Lacazella from the New Caledonian area.
The specimens described here are deposited in the collections of the Muséum national d'Histoire naturelle, Paris (NMHN BRA-3182-3210).
Remarks.This species is very rare in the investigated material, being found only at one station.However, it was already recorded from New Caledonia (Emig, 1988;Bitner, 2007a).Lingula anatina is characterized by an elongate, oblong outline with subparallel lateral margins (Emig, 1982(Emig, , 1984)).The valve surface is smooth with distinct growth lines.The shell colour is slightly greenish to brownish along the posterior and lateral margins.
The studied material is very limited, consisting of only one dorsal valve.However, it is consistent with that hitherto described (Dall, 1871(Dall, , 1920;;Davidson, 1888;Hatai, 1940;Harper, 1997).The shell is small, up to 5.4 mm in valve length, nearly circular in outline, conical.The apex, situated subcentrally, is smooth, marked only by concentric growth lines (Fig. 2B).The shell surface is ornamented by numerous, fine radial costae and concentric growth lines.
In size and in its fine, ribbed ornamentation D. stella is close to D. indica (Dall, 1920) from the Indian Ocean.These two species differ, however, in the character of the ribs, which are distinctly granular and more widely spaced in D. indica (Cooper, 1973b;Bitner et al., 2008a).
So far D. stella has been identified from off Japan and China to northern Australia (Hatai, 1940;Richardson et al., 1989;Emig, 1997;Harper, 1997).The present finding from off New Caledonia extends the biogeographical range of this species southwards.This is the first record of a discinid from New Caledonia.

Novocrania reevei
Remarks.This poorly known species was originally described as Crania suessii by Reeve (1862) from off eastern Australia.As the name suessi was preoccupied by an Upper Cretaceous species of the same genus, Lee and Brunton (1986) proposed its replacement by reevei.However, they did not re-describe and/or re-illustrate the species.It is worth mentioning that the reproduction of Reeve's (1862) figure presented by Davidson (1888) shows the ribbed surface of Crania suessii (=N.reevei), which is not in accordance with the original figure, where only the colour pattern is indicated.The specimens described as Novocrania sp. from two nearby archipelagos, Fiji and Wallis and Futuna (Bitner, 2008), are consistent with the specimens investigated here, so they are included in synonymy of N. reevei.
Externally N. reevei is close to the Antarctic species N. lecointei (Joubin, 1901), which also has a finely pustulose surface (Foster, 1974).It differs, however, in being much smaller and having more distinct, elevated anterior adductor scars.Also, the specimen described by Cooper (1981) from south of Madagascar as Crania sp. has a pustulose exterior but its surface is smooth with regular growth lines (Cooper 1981: pl. 13, Fig. 4), not resembling that of N. reevei.Internally Crania sp. is readily distinguishable from the New Caledonian specimens in having much smaller posterior adductors and no elevated anterior adductor scars.The studied specimens are also similar externally to N. indonesiensis (Zezina, 1981a), but differ strongly internally; in N. indonesiensis muscle impressions are indistinct and differently arranged (Zezina, 1981a).N. reevei is easily distinguishable from the New Zealand species, N. huttoni (Thomson, 1916) by its shell ornamentation; in N. huttoni the shell surface is covered with radial ribs (Thomson, 1916;Lee, 1987).
In the lack of separation of the brachial retractor scars from the adductors, Novocrania reevei resembles N. turbinata (Poli, 1795) from the northeastern Atlantic and the Mediterranean (Logan and Long, 2001;Kroh et al., 2008).It differs, however, from N. turbinata in having a pustulose outer surface and much more elevated anterior adductor muscle scars.Additionally, N. turbinata is twice as large as N. reevei (Logan and Long, 2001).It is also worth noting that the presence of N. turbinata has been recently mentioned from the New Zealand region (MacFarlan et al., 2009).
From the New Caledonia region one more craniid species, Neoancistrocrania norfolki Laurin, 1992 has already been reported (Laurin, 1992(Laurin, , 1997;;Bitner, 2009).This species is characterized by thick, massive valves, thus differing strongly from N. reevei.The two species also differ externally; in N. norfolki the shell surface is smooth without pustules.In turn, the presence of two erect processes on the dorsal valve in N. norfolki distinguishes this species internally from the specimens studied here.
Originally E. rugosa was described from the Philippines (Cooper, 1973a).However it has a wide distribution in the western Pacific, from the southern Emperor Seamounts to Tasmania (Zezina, 1981b, c;Bitner, 2008), and it has also been recorded from the western part of the Indian Ocean (Zezina, 1987(Zezina, , 1994)).

Argyrotheca mayi
Recently Álvarez et al. (2008) erected a new genus Joania for those Argyrotheca species having a narrow hinge line, prominent cardinal process and tubercles on the inner valve margins.In the subtriangular outline and narrow hinge line A. mayi resembles the genus Joania but it differs in having a small cardinal process and lacking margin tubercles (Hiller et al., 2008: Fig. 5).This is the first record of the genus Argyrotheca from the New Caledonian region.Material examined: New Caledonia, Secteur de Poindimié: stn 830, two complete specimens.

Argyrotheca neocaledonensis
Diagnosis: A very small, transversely subpentagonal Argyrotheca with smooth surface and wide hinge line; teeth wide, parallel to the hinge line.
Etymology: The species is named after New Caledonia, the type locality.
Ventral valve interior with short wide teeth lying parallel to the hinge line.Pedicle collar wide, excavated anteriorly, supported by median septum that extends to 2/3 of the valve length.Dorsal valve interior with high inner socket ridges and prominent cardinal process.Crura thick, very short; crural processes short.Descending branches unite valve floor posteriorly and reappear anteriorly to overgrow the septum.Median septum triangular in profile, short but high with 2 serrations.Muscle scars distinct on both valves, marked as suboval depressions.
Remarks.Specimens of the genus Argyrotheca are very rare in the Pacific, but so far those described belong to three species.The studied specimens are close in outline to A. australis (Blochmann, 1910).They differ, however, from this South Australian species in having a smooth surface and internally in having wide teeth; the teeth in A. australis are hooked (Hiller et al., 2008).From A. mayi the discussed specimens differ in outline; A. mayi has an elongate triangular outline with a short hinge margin (Hiller et al., 2008).Also teeth in A. neocaledonensis and A. mayi display a strong difference, being short and wide in the former, and hooked in the latter.
The investigated specimens are easily distinguishable from A. arguta Grant, 1983 from Bikini Atoll in lacking tubercles on the inner margin (Cooper, 1954;Grant, 1983).Also the specimens from Fiji described as Argyrotheca sp.(Bitner, 2008) posses tubercles on the valve margin that clearly distinguishes them from A. neocaledonensis n. sp.The presence of tubercles and a distinct cardinal process in A. arguta and Argyrotheca sp. from Fiji may indicate that those species should better be placed in the newly created genus Joania Álvarez, et al., 2008. Superfamily Terebratelloidea King, 1850 Family Dallinidae Beecher, 1893 Subfamily Nipponithyridinae Hatai, 1938 Genus Campages Hedley, 1905 Type species.Campages furcifera Hedley, 1905.

Dimensions (in mm): Station number
Length Width Thickness 830 9.5 7.0 5.4 858 8.9 6.6 5.0 Remarks.This species has already been reported from the New Caledonia region (Bitner, 2009).It is characterized by distinct growth lines and a folded anterior commissure (Cooper, 1970).The investigated specimens are immature, as shown by their small size and large foramen.C. mariae is restricted to the western Pacific (Hatai, 1940;Richardson et al., 1989;Logan, 2007;Bitner, 2009).
Description.Shell small, subtriangular, ventriconvex, dorsal valve nearly flat, transversely oval, wider than long.Shell surface irregular, growth lines visible.Interarea with upraised triangular pseudodeltidium (Fig. 6C).Hinge line straight.Anterior commissure rectimarginate.Cardinal process prominent, slightly trilobed.Rim papillose.Bridge broken in all specimens.Median septum divided to form a trifurcating structure consisting of a pair of crescentic lateral ramuli and a median ramus which ends posteriorly in a pointed lobe.(Fig. 6A, F).Median depression wide.Two major (outer) interbrachial lobes well defined.Two minor (inner) lobes slightly divergent and interdigitating with posterior part of median ramus.Margins of interbrachial lobes smooth.
Remarks.The material is represented by the dead shells, rather poorly preserved.The articulated specimen with pseudodeltidium represents most probably the genus Lacazella but all attempts to open the shell failed, precluding examination of dorsal and ventral valve interiors.None of the dorsal valves is completely preserved, so not all the characters can be observed.In consequence, specific determination of this material is not possible.This is the first description of Lacazella from the Pacific Ocean and the first record of this genus from the New Caledonian region.However, the presence of an undescribed Lacazella species in submarine caves of Okinawa, Japan has been mentioned by Saito et al. (2000) and by Motchurova-Dekova et al. (2002).
To date, three extant species of Lacazella have been described (Logan, 2007).The type species, L. mediterranea (Risso, 1826) from the Mediterraneam Sea (Logan, 1979;Álvarez and Emig, 2005) is regarded as neoendemic to the Mediterranean (Logan et al., 2004).It differs from the New Caledonian Lacazella sp. in having denticulated ascending lobes.The only Indian Ocean species, L. mauritiana Dall, 1920 is very similar to L. mediterranea (Cooper, 1973b: pl. 1, Figs. 7-9) in having denticulated lobes, thus differing from Lacazella sp.described here.In turn, L. caribbeanensis Cooper, 1977 from the Caribbean Sea like the investigated specimens, has smooth margins to its ascending elements (Cooper, 1977).L. mediterranea, L. mauritiana and L. caribbeanensis also differ from each other in the internal features of the ventral valve, which was not available for study in the present material.

DISCUSSION
To date, very little has been known about the shallow-water brachiopods of the New Caledonian region (Emig, 1988;Bitner, 2007a), though more is known about the deep-sea benthic communities.The brachiopod collection described here was obtained from the shallow waters around the main island of New Caledonia.It consists of 12 species belonging to 10 genera: Lingula anatina Lamarck, Discradisca stella (Gould), Novocrania reevei Lee and Brunton, Xenobrochus africanus (Cooper), Eucalathis rugosa Cooper, Frenulina sanguinolenta (Gmelin), Argyrotheca mayi Blochmann, A. neocaledonensis n. sp., Campages mariae (Adams), Thecidellina maxilla (Hedley), T. minuta Cooper, and Lacazella sp.Six of them, X. africanus, E. rugosa, F. sanguinolenta, C. mariae, T. maxilla, and T. minuta, were also reported from deep water in the New Caledonian region (Laurin, 1997;Bitner, 2009) while L. anatina is known only from shallow water (Emig, 1988;Bitner, 2007a).Five species are reported for the first time from the New Caledonian region.
Discradisca stella is not only the first record of the genus and species but also the first record of discinid brachiopods in the New Caledonian region.Also N. reevei represents the first record of the genus Novocrania from New Caledonian waters.This species was originally described from off eastern Australia (Reeve, 1862).It has been also earlier reported from off Fiji, but because of the limited material it was described in open nomenclature (Bitner, 2008).
Most interesting is the finding of two megathyridid species, Argyrotheca mayi and A. neocaledonensis, and a thecideide, Lacazella sp.Both genera represent the first records in the studied area.Argyrotheca is a very rare genus in the Pacific (Cooper, 1954;Grant, 1983;Bitner, 2008;Hiller et al., 2008), being known from off Australia, the Marshall Islands and Fiji.However, at least two species of Argyrotheca were reported from the submarine caves in the Ry-ukyu Islands, Japan (Saito et al., 2000); the material has never been taxonomically described.The genus Lacazella was also recorded, but not described, from the submarine caves of Japan (Saito et al., 2000).In this report Lacazella is for the first time described and illustrated from the Pacific Ocean.In the Pacific two species of another lacazelline genus, Ospreyella, have been reported: O. depressa Lüter from the Great Barrier Reef of Australia and O. palauensis Logan from Palau, northwestern Pacific (Lüter et al., 2003;Logan, 2008).Some investigated brachiopod specimens show evidence of gastropod predation activity.The highest frequency of drill holes is observed in Frenulina sanguinolenta and Eucalathis rugosa, where 24 (32.4%) and 17 (7.9%)specimens, respectively were drilled.No predation activity was observed in the cementing forms Novocrania reevei, Thecidellina species and Lacazella sp., or on either species of Argyrotheca.
With 5 species reported in the present study for the first time from New Caledonia, the total number of species from this region increases to 43 (d 'Hondt, 1987;Emig, 1988;Laurin, 1997;Bitner, 2007aBitner, , 2009;;Bitner et al., 2008b), exceeding the New Zealand region, where 40 species are recorded (MacFarlan et al., 2009).The New Caledonian brachiopod fauna shows the greatest affinity to the fauna from Fiji, sharing 15 genera and 11 species (Bitner, 2006b(Bitner, , 2008)).Due to the new discovery of Discradisca, Novocrania and Argyrotheca, the number of common genera and species with Australia and New Zealand increases to 12 genera and 7 species in Australia and 12 genera and 6 species in New Zealand.Also, earlier studies showed closer affinities between New Caledonian and Fijian faunas than between New Caledonian and Australian and New Zealand faunas (Bitner, 2009), although today's surface current system would rather suggest affinities between New Caledonia and Australia.Such a pattern may be better understood in the light of the geological history of this region.In the early Tertiary New Caledonia and Fiji were geographically closer than today (Johnston, 2004: Fig. 5), suggesting easy exchange of faunas.In the Middle Miocene, clockwise rotation of the Vanuatu arc caused the shifting of Fiji to the east, separating New Caledonia and Fiji from each other.The biogeographical pattern of brachiopod distribution in the South-West Pacific is more readily explained by vicariance (Humphries and Ebach, 2004;Heads, 2009), when geological processes such as plate tectonics led to separation of regions and their faunas, than by simple dispersal (see also Bitner, 2009).
Technical limitations in collecting shallow-water faunas caused undersampling of such areas around New Caledonia (see Richer de Forges, 1991: p. 17), so it is probable that further investigations could increase the number of shallow-water brachiopod species from this region.In particular, cryptic habitats are potentially a good source of new forms.

Fig. 1 .
Fig. 1. -Map of New Caledonia, showing location of the dredging stations where brachiopods were found.

Table 1 .
-Locality data and species distribution among the stations.