Distribution of deep-sea benthic foraminifera in the Neogene of Blake Ridge, NW Atlantic Ocean

This study describes and illustrates the evolution of deep-sea benthic foraminifera from the Blake Ridge during the late Neogene. In total, 305 species of benthic foraminifera belonging to 107 genera were identified. The Blake Ridge receives fine-grained nannofossil-bearing hemipelagic sediments, transported from the Canadian continental margin by the Deep Western Boundary Undercurrent (DWBUC). We thus presume that changes in benthic foraminifera at Ocean Drilling Program (ODP) sites 991A, 994C, 995A and B and 997A reflect mainly changes in the intensity of the DWBUC, which is closely related to North Atlantic Deep Water (NADW) production. However, the dominance of Uvigerina peregrina , U. proboscidea and Cassidulina carinata during the late Miocene in all the holes suggests an increased influence of Southern Component Waters in the Blake Ridge region. During the early Pliocene (4.8–2.8 Ma) in all the sites benthic faunal assemblages suggest that there was an increased transport of organic-rich sediments by the DWBUC from the Canadian margin to the Blake Ridge, driven by increased production of NADW. During this time the species diversity (Sanders9 rarefied values) was low. In the younger interval (since 2.8 Ma), the faunal data suggest less transport of organic-rich sediments to the Blake Ridge, which appears to be related to weakening of the DWBUC during cold intervals. An increase in species diversity at 3 Ma probably resulted from decreased population of bacteria due to low organic matter and/or less competition. In the late Pleistocene ( c . 0.6 Ma), Stilostomella lepidula became extinct in all the studied holes, suggesting that this species may have possessed a mode of feeding which no longer existed in the cold, well-oxygenated oceans of the present.


INTRODUCTION
Benthic foraminifera are an important source of information on past environmental variability. This group occupies perched epibenthic to deep infaunal microhabitats, utilizing a variety of trophic mechanisms. Benthic foraminifera are able to survive/ proliferate in a wide range of marine environments, including extreme ecosystems, such as oligotrophic abyssal plains (Coull et al., 1977) or hydrothermal vents (Sen Gupta & Aharon, 1994), cold seeps (Rathburn et al., 2000;Bernhard et al., 2001;Robinson et al., 2004) and deep sea trenches (Akimoto et al., 2001).
At present, the flanks of the Blake Ridge above c. 3500 m are covered by the Northern Component Waters (NCW), carried by the DWBUC to the south, with a density of c. 27.88 kg m -3 and a dissolved oxygen concentration of c. 6.3 ml l -1 (Bower & Hunt, 2000). At depths greater than c. 4000 m, the ridge is covered by Southern Component Waters (SCW), mainly fed by the Antarctic Bottom Water (AABW). This deep bottom water, however, consists of a varying mixture of NCW (up to 90%) and SCW (Stahr & Sanford, 1999). There have been few studies to reconstruct the relative volume of NCW and SCW during earlier time periods. Frank et al. (2002) and Reynolds et al. (1999) used Nd and Pb isotopes to argue that the export of the SCW was strong prior to 3 Ma, and linked changes in Pb isotope values after 3 Ma and more dramatic changes since 1.8 Ma to the North Atlantic circulation as related to the Northern Hemisphere glaciation (NHG).
The Blake Ridge archives a continuous and thick sedimentary record, providing ample opportunities to examine a link between benthic foraminiferal populations, DWBUC and deep water masses influenced by NCW and SCW. To understand this relationship, we analysed population trends in dominant benthic foraminifera and Sanders' rarefied values from five Ocean Drilling Program (ODP) holes, 991A, 994C, 995A and B and 997A, drilled during Leg 164 on the Blake Ridge, NW Atlantic Ocean. We also document and illustrate important benthic foraminiferal species with scanning electron micrographs that give an idea about the state of preservation of benthic fauna in the Blake Ridge.

LOCATION AND OCEANOGRAPHIC SETTING
Ocean Drilling Program (ODP) holes 991A, 994C, 995A, 995B and 997A (Leg 164) are located on the Blake Ridge, c. 200 km off the east coast of the USA in the NW Atlantic Ocean (Fig. 1, Table 1). These holes lie in a tectonically inactive setting close to the passive margin and were not affected by late Cenozoic tectonic activity or by fluid flow along major faults in the sediments (Wood & Ruppel, 2000). Site 991, hole A lies near the upslope flank of the Cape Fear Diapir, where sediments that may formerly have contained gas hydrate have been disturbed (Paull et al., 1996). This hole has three or more discrete mass-transport zones of different ages ranging from the Miocene to the Pleistocene, punctuated by undisturbed sediment intervals. The geological setting of Site 995 is similar to that of Sites 994 and 997. These sites are located on the southern flank of the Blake Ridge -a Neogene sediment drift (Tucholke & Mountain, 1979). The depth and speed of the DWBUC have varied on glacial-interglacial time-scales, with shallower depth and slow speed related to the increased influence of SCW (AABW) during the late Miocene to the Pleistocene (Ledbetter & Balsam, 1985). The depth of the contact between NCW (above) and SCW (below) has changed significantly over time, generally shallowing by more than 2000 m during glacial intervals, so that the DWBUC's zone of maximum flow speed shifted to a depth of less than 2500 m (Evans & Hall, 2008). The major increase in DWBUC depth during interglacials and speed correlates with the resumption of North Atlantic Deep Water (NADW) production (Shackleton et al., 1983).
The depositional environment at Blake Ridge is strongly influenced by glacial-interglacial switches in the strength and position of the DWBUC that preferentially eroded sediments from the Canadian continental margin (Laine et al., 1994) and led to the sediment drifts in the Blake-Bahama Outer Ridge (BBOR) region (Franz & Tiedemann, 2002). These drift deposits consist of cyclic alternations between carbonate-rich and clayrich sediments with higher carbonate concentrations during interglacial stages. Because NADW circulation enhances speed of DWBUC, and NADW production is higher during interglacials (Franz & Tiedemann, 2002), it is expected that the DWBUC will intensify sediment transport from the Canadian continental margin during interglacial periods.
The modern lysocline in the Blake Ridge area lies between 4000 m and 4350 m water depth (Balsam, 1983). The only tectonic event that occurred adjacent to the study area is the closing of the Panama Isthmus around 4 Ma, which drove significant changes in the thermohaline circulation of the North Atlantic (Haug & Tiedemann, 1998).

MATERIALS AND METHODS
One thousand five hundred and sixteen (1516) core samples were analysed, which were provided under request numbers 16030A, 16030B and 16030C to AKG. From hole 991A we analysed 179 samples, with a total length of 56.6 m below seafloor (mbsf), ranging from 5.9 Ma to the Recent; from hole 994C, 441 samples (up to 703.5 mbsf), covering the last 6.8 Ma; from hole 995A, 599 samples (up to 704.10 mbsf), ranging from 6.6 Ma to the Recent; from hole 995B, 59 samples (up to 453.06 mbsf), with a total duration of 4.9 Ma; and from hole 997A, 238 samples (up to 434.3 mbsf), spanning the last 5.4 Ma (Table 1).
Samples were processed with the necessary precautions to avoid contamination using the standard procedures (Gupta & Thomas, 1999). Samples were soaked in clean tap water with few drops of hydrogen peroxide (H 2 O 2 ) of 3-5% concentration for  --------------------------------Late Miocene to Recent --------------------------------© 8-12 hours and were washed over a 63 µm size sieve. The washed samples were dried in an electric oven at c. 50(C and transferred into labelled glass vials. We generated benthic foraminiferal census data from an aliquot of c. 300 specimens from the > 125 µm size fraction. The specimens were counted, identified, their stratigraphic ranges plotted and percentages calculated (data available at www.pangaea.de). Sanders' rarefied values were calculated following the procedure described in Singh & Gupta (2004). All samples are catalogued in the Paleoceanography and Paleoclimatology Laboratory of the Department of Geology & Geophysics, Indian Institute of Technology, Kharagpur. Scanning electron micrographs were taken at the SEM laboratory of the Department of Geology & Geophysics and Central Research Facility (CRF), Indian Institute of Technology, Kharagpur.

RESULTS
We identified 305 species of benthic foraminifera belonging to 107 genera. Out of these, 158 species belonging to 83 genera are shown in Plates 1-13. These species are listed in Appendix A. Some 262 species were identified at hole 991A, 220 species at hole 994C, 245 species were recorded at hole 995A, 148 species at hole 995B and 160 species at hole 997A.  (Figs 4,6), whereas at site 991 these species show secular trends, with less significant populations. Globocassidulina obtusa and Epistominella sp. show higher abundances in the Pliocene (5-3 Ma) and during 1.8-1.0 Ma at site 991, whereas at sites 994, 995 and 997 these species are abundant in the younger interval with more dominance during 1.8-1.0 Ma. At sites 994, 995 and 997, Uvigerina proboscidea and Globocassidulina subglobosa show higher abundances during 6.8 to 3.0 Ma, Astrononion stelligerum appears at c. 3.2 Ma, A. umbilicatulum shows higher abundances during 2.6-0.6 Ma, Epistominella exigua and Pyrgo murrhina show low abundances during 5-3 Ma and Melonis barleeanum remains abundant throughout the studied section, with a higher population during 5-3.5 Ma (Figs 4, 6). At site 991, Epistominella exigua and Pyrgo murrhina are also rare in the Pliocene, showing an inverse relationship with Globocassidulina obtusa.
Sanders' rarefied values show a major increase at c. 5.3 Ma and a second increase at c. 3 Ma at hole 991A, coinciding with the onset of NHG (Zachos et al., 2001;Fig. 7). At holes 994C, 995A and 997A, these values show a major increase at c. 3 Ma with abrupt changes in the younger interval (Fig. 7).

ECOLOGICAL PREFERENCES OF BENTHIC FORAMINIFERA
Benthic foraminifera live in variable ecological settings depending on their physiological and food requirements. Some species prefer to live in eutrophic, low-oxygen conditions, whereas others prefer to live in oligotrophic, better oxygenated conditions. Some are opportunists, whereas many species of benthic foraminifera are specialists. The following text details modern ecological preferences of the different benthic foraminiferal species used in the present study for palaeoceanographic reconstructions.
Astrononion umbilicatulum in the Red Sea shows a preference for high salinity waters (Gupta, 1994). This species is found during low productivity intervals on the Ontong-Java Plateau (Burke et al., 1993;Gupta, 1997). Astrononion umbilicatulum (synonymous with A. echolsi) has been found to be associated with lowest primary productivity and a well-ventilated water column in the Gulf of Aden (Almogi-Labin et al., 2000). This species prefers a well-ventilated deep-sea environment with low organic carbon flux in the southeastern Indian Ocean (Singh & Gupta, 2004). Little or nothing is known about the ecological preference of Astrononion stelligerum. Its rare occurrence and similar population trend with A. umbilicatulum in this study suggests that this species prefers conditions identical to those of A. umbilicatulum.
Cassidulina carinata is a cosmopolitan, epifaunal to shallow infaunal, detrivorus, opportunistic taxon (Nees & Struck, 1999;Hayward, 2002) and has been reported from diverse environments (Qvale & Van Weering, 1985). This species responds positively to increasing input of fresh phytodetritus or labile organic matter to the ocean floor (Fontanier et al., 2003). In the Mediterranean Sea, C. carinata requires relatively eutrophic conditions of >3 g of labile carbon m -2 year -1 to flourish (De Rijk et al., 2000). In the Indian Ocean, an assemblage dominated by C. carinata and Gyroidinoides nitidula reflects an environment with intermediate organic flux and intermediate to high seasonality (Gupta & Thomas, 2003). In addition, association of this species with Uvigerina proboscidea in the Indian Ocean indicates low oxygen conditions with continuous high food supply (Gupta, 1997;Gupta & Thomas, 1999). Cassidulina carinata is common in the lower part of the oxygen minimum zone (OMZ) Deep-sea benthic foraminifera in the Neogene, NW Atlantic Ocean off the Pakistan continental and Oman margins (Hermelin & Shimmield, 1990;Jannink et al., 1998). In the South Atlantic Ocean, it has been found correlated with the highest productivity and high organic carbon flux (Mackensen et al., 1995) and in the southeastern Arabian Sea this species is associated with high food supply (Gupta & Thomas, 1999). Dominance of C. carinata in bathyal environments testifies to the broad habitat preference of this species and also its association with cold temperatures which prevail in bathyal settings below the thermocline (Hayward, 2002).
Epistominella exigua is a cosmopolitan species which feeds opportunistically on phytodetritus, deposited seasonally on the sea floor and usually associated with elevated oxygen concentrations (Gooday, 1988(Gooday, , 1993Kurbjeweit et al., 2000;Gupta & Thomas, 2003). Earlier studies observed dominance of E. exigua in the eastern and southern Indian Ocean at abyssal depths (Corliss, 1983;Peterson, 1984). Gooday (1993) correlated increased abundance of E. exigua with seasonal pulses of food supply. Also, in the eastern Indian Ocean, these food fluxes were related to the monsoonal climate where E. exigua thrives in deep environments with a temperature of c. 2.5(C and oxygen of >3.5 ml l -1 (Murgese & De Deckker, 2005). Epistominella exigua has an advantage over other species when there is an input of fresh, labile organic matter (Caralp, 1989b;Gooday, 1994). The microhabitat preference Globocassidulina obtusa has been found associated with an assemblage linked to high productivity and low oxygen environments (Gupta & Thomas, 1999). Singh & Gupta (2004) suggested that this species is an indicator of intermediate to high sustained flux of organic matter to the sea floor in the southeastern Indian Ocean.
Globocassidulina subglobosa is a cosmopolitan species occurring over a wide range of bathymetry with different water masses, largely reflecting well-oxygenated deep waters with strongly pulsed food supply and good carbonate preservation in commonly oligotrophic environments (Singh & Gupta, 2004) in the southeastern Indian Ocean. Fariduddin & Loubere (1997) observed this species associated with NADW in the Atlantic Ocean and categorized it as a low productivity species, whereas Corliss (1979) found it associated with AABW in the southwest Indian Ocean. This taxon is often found abundant in sediments receiving less organic matter in regions where strong bottom currents are likely to occur Nees & Struck, 1999). Ohkushi et al. (2000) suggest that Globocassidulina lives in areas of enhanced and continuous food supply. In the south Atlantic, high abundances of G. subglobosa are found within the depth range of Circumpolar Deep Water (Schnitker, 1980) and in oligotrophic areas at higher elevations of ridges and submarine hills (Mackensen et al., 1995). Gooday (1994) suggested that G. subglobosa feeds on phytodetritus, reflecting pulsed food supply to the ocean floor. This species is thus Deep-sea benthic foraminifera in the Neogene, NW Atlantic Ocean  suggestive of NADW and appears to be an opportunist with great powers of adaptation.
High abundances of Melonis barleeanum in the north Atlantic are characteristic of high productivity regions with sustained flux of organic matter to the sea floor (Thomas et al., 1995). Extraordinary high abundance of this species in the eastern south Atlantic indicates a strong supply of organic matter to the sea floor . Evenly distributed pores on the test of infaunal species Melonis barleeanum suggest an adaptation to gas exchange in low oxygen conditions (Corliss, 1985;Fontanier et al., 2005) and during high food supply (Arnold, 1983;Caralp, 1988  organic matter (Gupta & Thomas, 2003). It has also been reported as high productivity taxon from the Pacific Ocean (Loubere, 1991(Loubere, , 1994. In hydrocarbon-seep environments, M. barleeanum is common due to the availability of bacteria as the source of food (Boetius et al., 2000;Panieri, 2005).
Stilostomella lepidula is a cosmopolitan taxon, which reflects complicated ecological preferences that are yet to be fully understood. Boersma (1990) suggested that S. lepidula prefers to live in sediments that are organic carbon rich and moderately low in oxygen. In the present study, S. lepidula disappears across the mid-Pleistocene Transition (MPT) which has also been observed in earlier studies (Gupta, 1993;Hayward, 2001;Kawagata et al., 2006). The extinction of this species across the MPT has further complicated our understanding of its ecological preference. Values were calculated using the method described in Singh & Gupta (2004). A major increase at c. 3 Ma in holes 994C, 995A and 997A coincides with the beginning of major Northern Hemisphere glaciation. For grey bars and hatched area, see Fig. 3.
The environmental preferences of Quadrimorphina laevigata are not well constrained. This species has been found associated with Bolivina paula, Bulimina striata, Cassidulina laevigata, Epistominella exigua and Globocassidulina obtusa, which are suggestive of high organic carbon and low oxygen environments.
The genus Uvigerina is commonly known as a high productivity taxon (Loubere, 1991(Loubere, , 1994Rathburn & Corliss, 1994). The shallow infaunal Uvigerina peregrina is closely related to continuous organic carbon flux irrespective of oxygen levels (Miller & Lohmann, 1982;Rathburn & Corliss, 1994;Mackensen et al., 1995). In a recent study, De & Gupta (2010) observed the dominance of Uvigerina peregrina in the oxygen minimum zone (OMZ) of the northwest Arabian Sea, where surface productivity is highest and oxygen is at a minimum. It was also reported as a dominant species from below the OMZ by previous workers, from the northwest (Hermelin & Shimmield, 1990), as well as the northeast (Jannink et al., 1998;Maas, 2000;Schumacher et al., 2007), Arabian Sea where there is high flux of organic matter (Jannink et al., 1998;Schumacher et al., 2007). Altenbach & Sarnthein (1989) and Fontanier et al. (2002) suggested that U. peregrina prefers a microhabitat rich in bacteria, exoenzymes and meiofauna, and is typical of sediments enriched in organic carbon and depleted in oxygen, which is common in areas below upwelling productivity zones. Fontanier et al. (2002) and Geslin et al. (2004) argued that this species has a variable response to varying oxygen conditions. In a recent study, this species was observed to tolerate in situ a temperature range of 10.6-13.9(C, oxygen 0.25-0.56 ml l -1 and a large range of primary production (De & Gupta, 2010).
Uvigerina proboscidea blooms in high productivity regions of the Indian Ocean (Gupta & Srinivasan, 1992;Gupta & Thomas, 1999;Almogi-Labin et al., 2000), particularly when productivity is high throughout the year and seasonality of food supply is low or absent (Loubere, 1998;Gupta & Thomas, 1999;Loubere & Fariduddin, 1999;Ohkushi et al., 2000). This species is correlated positively with organic carbon flux and negatively with dissolved-oxygen concentration in the eastern Indian Ocean (Murgese & De Deckker, 2005). Uvigerina proboscidea was reported by Gupta (1994) from 1200-5000 m water depth in the Recent sediments of the Indian Ocean, with the highest abundance between 1700 m and 2300 m in the eastern sector. Peaks of U. proboscidea abundances are inferred to represent times of high surface productivity related to intense trade winds during the SW Indian monsoon causing widespread upwelling along equatorial divergence in the Indian Ocean (Gupta & Srinivasan, 1992). In Recent sediments of the Indian Ocean, U. proboscidea is found in conditions of in situ temperature of 2.1-9.5(C, oxygen from 0.96-3.29 ml l -1 and high phosphate and nitrate concentrations (De & Gupta, 2010).

DISCUSSION
Recent studies suggest that, in general, benthic foraminiferal distribution is limited by a combination of food availability and oxygenation (Sen Gupta & Machain-Castillo, 1993;Jorissen et al., 1995;Gooday, 2003). However, in areas where the oxygen content of bottom waters is not a limiting factor, the amount of organic flux to the sea floor mainly governs the occurrence of benthic species in the sediments ( Van der Zwaan et al., 1999;Friedrich & Hemleben, 2007).
Benthic foraminiferal faunas from sites 991, 994, 995 and 997 suggest significant palaeoceanographic changes in the Blake Ridge area during the late Miocene to the Pleistocene. We did not observe any species or species assemblage endemic to Blake Ridge methane settings, which supports the earlier findings of Panieri & Sen Gupta (2008) and Lobegeier & Sen Gupta (2008), for example, and thus we interpret benthic faunal data from this region in terms of organic food supplied by the DWBUC, linked to the intensity of NADW or NCW. Since hole 991A lies on a diapir, having both disturbed and undisturbed sediment column, we interpret faunal data from this hole cautiously. At hole 991A, the older interval (6-3 Ma), covering the gas hydrate zone, may have suffered some disturbance in the sediment column, whereas the younger interval appears to be undisturbed. Benthic faunas (e.g. G. obtusa, M. barleeanum) at hole 991A suggest high organic flux during 4.8-2.8 Ma, which corresponds to the early Pliocene warm period preceding major NHG. The high organic carbon during the early Pliocene warmth resulted from increased transport of terrigenous matter rich in refractory organic material from the continental margin of Canada by the DWBUC in response to increased production of the NADW (Laine et al., 1994;Balsam & Damuth, 2000). It has been widely suggested that NADW flow increases during warm intervals and decreases during colder periods (Raymo et al., 1990(Raymo et al., , 1996Kim & Crowley, 2000). At sites 994, 995 and 997, the early Pliocene interval is marked by higher abundances of G. subglobosa, M. barleeanum, U. peregrina and U. proboscidea, indicating increased availability of organic carbon. These species corroborate that during warm intervals there was increased transport of organic-rich sediments by the NADW-driven DWBUC to the Blake Ridge. Although there is not a one-to-one correlation between benthic data from site 991 and combined data from sites 994, 995 and 997, the overall trends are similar between the two areas.
From 2.8 to 1.8 Ma, the G. obtusa population decreases, whereas P. murrhina and E. exigua show an increase at all the studied sites (Figs 3, 4), indicating oligotrophic and welloxygenated conditions at the Blake Ridge. This was an interval of intensified NHG and decreased production of the NADW, resulting in weakening of the DWBUC and apparent decreased transport of nutrients to the Blake Ridge. An increase in species diversity (Sanders' rarefied values) at 3 Ma probably resulted from a decreased population of bacteria due to low organic matter and/or less competition. Singh & Gupta (2005) observed a similar relationship between benthic foraminifera and bacteria-rich organic carbon in the eastern Indian Ocean ODP hole 757B. An abrupt increase in G. obtusa and decrease in P. murrhina at hole 991A during 1.8-1.0 Ma indicates another pulse of increased transport of organic-rich sediments to the Blake Ridge. However, such a faunal pattern does not exist at holes 994C, 995A, B and 997A, where the species C. carinata and S. lepidula show episodic occurrences (Fig. 6), although Sanders' values show a short-lived decrease during 1.8-1 Ma (Fig. 7). We argue that these faunal trends indicate decreased delivery of organic-rich sediments by DWBUC to the Blake Ridge region following NHG, which may have benefited the opportunistic benthic species. The shipboard scientific data suggest decreased total organic carbon and sediment accumulation rates, and increased calcium carbonate (wt%) in the late Deep-sea benthic foraminifera in the Neogene, NW Atlantic Ocean Pliocene (c. 3 Ma) at Blake Ridge ODP holes (Paull et al., 1996). Thus, our observations strengthen a link between fauna and sediment characteristics at Blake Ridge.
In the late Pleistocene (c. 0.6 Ma), Stilostomella lepidula became extinct in all the holes studied (Figs 3-4). This species became extinct globally during the late Pleistocene cooling of the deep sea (Kawagata et al., 2005;Hayward et al., 2010). Stilostomella lepidula has complexly structured apertures, suggesting that it may have possessed a mode of feeding that no longer exists in the cold, well-ventilated oceans of the present (Hayward et al., 2010).

CONCLUSIONS
This study provides useful information about the transport of organic carbon-rich sediments by the Deep Western Boundary Undercurrent (DWBUC) to the studied sites, which provided a food source to benthic foraminifera in the Blake Ridge region. The sediment delivery to the Blake Ridge was closely related to the intensity of the DWBUC driven by production of the North Atlantic Deep Water (NADW). The enhanced population of uvigerinids in the late Miocene suggests an increased influence of the Southern Component Water (SCW). During the Pliocene warm interval (4.8-2.8 Ma) the intensity of DWBUC increased and enhanced the supply of terrestrial organic carbon to the Blake Ridge. The interval between 2.8 and 1.8 Ma coincides with the initiation of Northern Hemisphere glaciation (NHG), during which the production of NADW decreased and oligotrophic conditions prevailed. During 1.8-1 Ma, the faunal trends indicate decreased delivery of organic-rich sediments by DWBUC to the Blake Ridge region following the NHG. During the mid-Pleistocene Transition (c. 0.6 Ma), Stilostomella lepidula became extinct, which has been documented in the global ocean and related to the cooling of the deep sea.

ACKNOWLEGEMENTS
AKG thanks the Ocean Drilling Program (ODP) for providing core samples (under ODP request no. 16030A, 16030B and 16030C) for the present study. KM was supported by the Indian Institute of Technology, Kharagpur fellowship. The SEM Laboratories of the Department of Geology & Geophysics and Central Research Facility, IIT Kharagpur are gratefully acknowledged for taking the micrographs. Constructive reviews by two anonymous reviewers and the handling Editor are acknowledged with thanks.
Remarks. Not enough specimens found to assign any species name.