Antarctica, where turrids and whelks converge: A revision of Falsimohnia Powell, 1951 (Neogastropoda: Buccinoidea) and a description of a new genus

2013·9.5 MB·English

THE NAUTILUS 127(2):43-56, 2013 Page 43
Antarctica, where turrids and whelks converge: A revision
of Falsimohnia Powell, 1951 (Neogastropoda: Buccinoidea)
and a description of a new genus
Yuri I. Kantor M.G. Harasewych1
MRC
A.N. SevertzovInstituteof Ecology Departmentof Invertebrate Zoology, 163
and Evolution National Museum of Natural History
Russian Academyol Sciences Smithsonian Institution
Leninskyj Prospect, 33 P.O. Box37012
Moscow 119071, RUSSIA Washington, DC 20013-7012 USA
[email protected]
ABSTRACT havingnarrowdistributions, remainpoorlystudied. Among
the insufficiently studied groups within Antarctic waters
dAessctruidbyeodf tbhye tHyepermmaatneriSatlreobfelAntraervcetailcedspetchiaets offoucronospiedceiaenss, are the Conoidea. This superfamily is one of the most
all originally described in the genus Bela Gray, 1847 diverse clades of Neogastropoda (Bouchet, et ah, 2002;
(Mangeliidae), are referable to the superfamily Buccinoidea Bouchet, et ah, 2009), particularly in the tropics. The
basedon radularmorphology. Threeofthespecies: B fluvicans, classification of the superfamily Conoidea has recently
B. minor and B anderssoni are transferred to the genus been revised based on radular morphology (Tucker and
,
Falsimohnia, which is here reviewed. The new buccinoidean Tenorio, 2009) and molecular phylogeny (Puillandre
genus Strebela is proposed for the species originally described et ah, 2011), and now includes 15 families (Bouchet
as Bela notophila. Of the five species of the conchologically et ah, 2011). Thirteen of these families had previously
similargenusPareuthria Strebel, 1905thathavebeen recorded been included in a single family, the Turridae, which
within the Antarctic Convergence, two, Pareuthria innocens
(Smith, 1907) andP hoshiaii Numanami, 1996, aretransferred emerged as paraphyletic in the phylogenetic analysis.
to the genus Falsimohnia based on radular morphology. The These 13 families are collectively referred to here as
appropriategenericallocation ofPareuthriaplicataThiele, 1912 “turrids”. Currently, about 460 eonoidean genera and
is notyetclear; however, majordifferences in radularmorphol- subgeneraare recognized, 358ofwhichbelongto“turrid”
ogyexclude it from the genus Pareuthria. The taxa Pareuthria families and encompass more than 4000 named Recent
valdiviae (Thiele, 1925) and Pareuthria turriformis Egorova, species (Tucker, 2004), with many hundreds of species
W19e82suagrgeesptretsheanttltyhekynowiwlnl boenlyrefferrormedthteoirotshheerllgmeonreprhaolwohgeyn. stilTlhuenndiavmeersdit(yBoofucthuertr,idsetdaehc,re2a0s0e9)s.significantly in high
anatomical material becomes available, and that the genus latitudes. Onlyabout40species are known to inhabit the
Pareuthria wall belimitedtothe Magellanic region.
waters of the Arctic Ocean (Kantor and Sysoev, 2006).
Additional Keywords: Gastropoda, Conoidea, Buccinoidea, The diversity of turrids in Antarctic and subAntarcic
AntarcticConvergence,biogeography,morphologicalconvergence waters is alsoverylow. At present, 37 namedspecies have
been recorded from the Southern Ocean (Engl, 2012),
although there are still new species to be discovered and
named. Remarkably, the numberof presentlyrecognized
INTRODUCTION Arctic and Antarctic turrids is nearly the same.
The majority of the known Antarctic turrids were
Despite numerous and ongoing research programs described in publications based on the large Antarctic
that have been sampling areas of the Southern Ocean expeditions of the early 20th Century (Strebel, 1908,
for more than a century, many of the species of Thiele, 1912, Hedley, 1916). Hermann Strebel (1908)
Neogastropoda described from Antarctic waters are described numerous gastropods using material collected
known from a small numberofspecimens, and a consid- by the Swedish Antarctic Expedition (1901-1903) under
erable proportion ofthe taxa have yet to be re-sampled the command ofOtto Nordenskjold. Among these were
since their original description. Therefore, it is not sur- 11 new species ofturrids, of which ten were from within
prising that some ofthe smaller species, especially those the Antarctic Convergence (Strebel, 1908:87), the highest
number ofspecies ofAntarctic Conoidea to be described
1 Authorforcorrespondence in a single publication. All of the species described by
)
Page 44 THE NAUTILUS, Vol. 127, No. 2
Strebel were considered valid by most subsequent NHMUK: The Natural History Museum, London; SL:
authors (e.g., Powell, 1951, Engl, 2012). Five ofStrebels Shell length; SMNH: Swedish Museum of Natural His-
species are rather common in collections and are often tory,Stockholm;ZMB:ZoologicalMuseumofBerlin, Berlin;
referred to in the literature. 01 these, four serve as type ZSM, Zoologisehe Staatssammlung Miinchen, Munich.
species ofsubsequentlydescribed genera:
• Surcula magnified Strebel, 1908 =Aforia magnified, SYSTEMATICS
(
family Cochlespiridae Powell, 1942)
• Belaantarctica Strebel, 1908 (= Conorbela antarctica, Class Gastropoda Cuvier, 1797
type species of the genus Conorbela Powell, 1951, Order Neogastropoda Wenz, 1938
family Pseudomelatomidae Morrison, 1965) Superfamily Buecinoidea Rafinesque, 1815
• Bela pelseneri Strebel, 1908 (= Propebela (Lorabela Family Buccinulidae Finlay, 1928
pelseneri, type species of the subgenus Lorabela SubfamilyCominellinae Gray, 1857
Powell, 1951, family Mangeliidae P. Fischer, 1883)
Genus Falsimohnia Powell, 1951
• Bela purissima Strebel, 1908 (= Tijphlodaphne
purissima, type species of the genus Tijphlodaphne
Powell, 1951 family Borsoniidae A. Bellardi, 1875). Falsimohnia Powell, 1951: 137; Engl, 2012:145.
• Bela turrita Strebel, 1908 (—Belaturricula turrita
turrita, type species ofthe genus Belaturricida Powell, Type Species: BueeinumalbozonatumWatson,1882:358,
1951, family Borsoniidae) by original designation.
The remaining five Antarctic species described by Description: Shell small to medium-sized (to 12 mm),
Strebel (1908) as turrids are less well known, and all but broadly fusiform, with high, convex last whorl and short
Pleurotornella bathybia are reviewed here. Thanks to the to slightly attenuated canal. Protoconch paucispiral,
courtesy of Dr. Anders Waren we were able to study the smooth. Spiral sculpture usually of well-defined cords,
type material of Strebels species in the collections of covering entire shell surface. Axial sculpture of weakly
the Swedish Museum of Natural History, Stockholm, pronounced, low, narrow, broadly spaced, and slightly
including the radulae of three of the species. sigmoidal axial ribs most prominent on spire whorls.
The holotype of Pleurotornella bathybia had been lost Operculum oval, with terminal or subcentral nucleus,
some time ago, and a neotvpe (ZSM Mol 2002 1313) has situated in the lower corner ofoperculum. Radula with
only recently been designated (Engl, 2012: 185, pi. 76, rachidian teeth nearly as long as wide, V-shaped, with
fig. 2a) from off South Georgia, near the locality where deep anterior notch and long, single, medial cusp ema-
Strebels holotypewas collected. As this taxon is presently natingfrom posterior edge. Lateral teeth with long basal
known only from its shell and protoconch morphology, plate bearing two long, curved cusps near middle and
it is provisionallyretainedwithin Conoidea. inner margin of tooth. Outer portion of basal plate
The radulae and shell characters of the four species tapered, without cusps. Outer cusp broader, longer,
treated herein (all originallydescribed in the turrid genus inner cusp shorter, generally more curved.
Bela clearly demonstrate that these taxa belong in the
)
superfamily Buecinoidea. Badular morphology indicates Remarks: Powell (1951: 137) based his monotypical
aclose affinityto the genus Falsimohnia Powell, 1951. In genus Falsimohnia entirely on radular characters as a
this paper we review the genus Falsimohnia and include “derivative ofPareuthria in which the normal three cusps
aredescription offour ofStrebels species. of the central tooth have been reduced to a single
member”, noting also the similarity in the opereula of
the two genera. He designated Bueeinum albozonatum
MATERIALS AND METHODS Watson, 1882 from Kerguelen Island as the type species,
and went on to diagnose this genus by emphasizing
The type specimens of species described by Strebel eonehological similarities with the genera Pareuthria
are housed in Swedish Museum of Natural History. We Strebel, 1905 and Glypteuthria Strebel, 1905, but explic-
also examined specimens from the Museum national itlydifferentiated Falsimohnia on the basis ofits havinga
d’Histoirenaturelle, and the Institute Royal des Sciences radula similar to that ofthe Arctic genus Mohnia Friele,
Naturelles de Belgique forcomparative purposes. 1878, in which the rachidian tooth has a single cusp
Radulae were cleaned with diluted bleach (1 part of and the lateral teeth are bicuspid. The description of
commercially available bleach to 3-4 parts of distilled Falsimohnia did not provide any additional eonehological
water), mounted on roundglass coverslips and air-dried. or anatomical diagnosis.
Cover slips were then mounted onto SEM stubs, coated
with gold and examined under a }EOL JSM 840A scan- Falsimohnia albozonata (Watson, 1882)
ning electron microscope. Abbreviations used in text: (Figs 1-7, 13-19)
AL: Aperture length; AW: Aperture width; IRSN: Insti-
tute Royal des Sciences Naturelles de Belgique, Brussels; Bueeinum albozonatum Watson, 1882: 358; Watson,
MNHN: Museum national d’Histoire naturelle, Paris; 1886: 212, pi. 13, fig. 7.
Y. I. Kantor and M.G. Harasewych, 2013 Page 45
MNHN
Figures 1-12. Species of Fabimohnia. 1-7. Falsimohnia albozonata (Watson, 1882). 1-3. Shell, and 4. operculum,
uncataloged, Kerguelen Islands, lies Nuageuses, R/V Marion Dufresne, cruise 04, st. CP17, 48°47,1' S, 68°49.3' E, 70 in, (SL =
9.2 mm). 5-7. IRSN, IG 26482, Kerguelen Islands, S oflie Suhin, 40 m, (SL = 8.2 mm). 8-10. Falsimohnia cf. albozonata 8-9.
Shell and 10. operculum, MNHN uncataloged, Crozet Islands, RA7 Marion Dufresne, cmise 03, st. CP17, 46°24' S, 51°59' E, 180 in,
(SL = 6.0 mm). 11-12. Laclwsis australis Martens and Thiele, 1904. ZMB 59955, Syntypes. 11. This syntype (ZMR 59955a) is
designated as the lectotype ofLachesis australis Martens and Thiele, 1904, herein. 12. This syntype (ZMB 59955b) becomes the
paralectotypeofL. australis. The5 mm scalebarappliestoall shells, die 1 mm scalebarappliestoopercula.
Page 46 THE NAUTILUS, Vol. 127, No. 2
Figures 13-16. AnatomyofFalsimohnia albozonata. 13. Right lateral and 14. left lateralviews ofthe anterior foregut. 15. Right
lateral view or anterior foregut with right salivary gland removed to show the duct of the gland of Leiblein and valve of Leiblein.
16. Detail ofdistal end of penis, aoe, anterior oesophagus; dgl, duet ofthe gland of Leiblein; gL, gland ofLeiblein; lsd, duct of
the left salivary gland; lsg, left salivary gland; nr. circumoesophageal nerve ring; poe, posterior oesophagus; pr, proboscis; prr,
proboscis retractors; rhy, rhynchodaeum; rsd, ductof the rightsalivarygland; rsg, rightsalivarygland; sp, seminalpapilla;vL,valve
of Leiblein.
Lachesis? australis Martens and Thiele, 1904: 62, pi. 5, Nuageuses, R/V Marion Dufresne, cruise 04, st. CP17,
fig. 18. — 48°47.T S, 68°49.3' E, 70 m (Figures 1 A-D); MNHN,
Pareuthria albozonata Thiele, 1912: 244. uncataloged, Crozet Islands, R/V Marion Dufresne,
Falsimohnia albozonata—Powell, 1951: 138. cruise 30, st. DC60, 46°25' S, 50°22' E, 105-120 m
?Mangelia nigropunctata Martens, 1885: 91-92. (11 dead); MNHN, uncataloged, Crozet Islands, R/V
? Mangelia antarctica Martens and Pfeffer, 1886: pi. 1, Marion Dufresne, cruise03, st. CP17, 46°24' S, 51°59' E,
figs. 5 a, b. 180 in (1 live, radulaexamined, lightform) (Figures 8-10).
Type Localities: Royal Sound, Kerguelen Islands, Description: Shell medium-sized (to 10 mm), strong,
4K9e°r2g8u'elSe,n70I°sl13a'ndsE,(L2.8 afumstsral[i5s1)-.m]So(uB.thalGbeoozrogniaatu(mM.); sbhrooratd,lybrfouasdifosrimp,honwailth caenvaeln.lyPrcootnovceoxnchwhorrolusndaendd,
nigropunctata, M. antarctica). smooth, paucispiral. Axial sculpture limited to growth
lines, occasionally with narrow, broadly spaced, low,
Material Examined:, IRSN IG 26482, Kerguelen slightly prosoeline ribs more pronounced on upper
Islands, S ol lie Suhin,40m, 3live, 1 dissected(Figures 1 teleoeonch whorls. Spiral sculpture oflow rounded cords
E-G); MNHN, uncataloged, Kerguelen Islands, lies (9-11 on penultimatewhorl, 16-19 on lastwhorl) slightly
Y. I. Kantor and M.G. Harasewych, 2013 Page 47
MNHN
Figures 17-20. Falsimohnia albozonata radulae. 17-18. Radula of specimen in figures 1-3, uncataloged, Kerguelen
IIsRlSanNd,s,IGlie2s64N8u2a,geKuesregsu,elMeanriIosnlanDdusf,rSesonfeyli,ecrSuuliisien,044,0stm..C2P01.7,Fa4l8s°i4m7o,h1n'iSa,c6f8a°l4b9o.z3'onEa,ta70Rma.du1l9a.oRfasdpuelcaimofenspiencfiimgeurnesin8-fi9g,urMesN5H-7N,
uneataloged, Crozet Islands, R/V Marion Dufresne, cruise03, st. CP17,46°24' S,51°59' E., 180m. Scalebars = 10 pm.
narrower that the interstices. Aperture elongated (AIV Gross Anatomy: Last whorl of the animal of a single
SL ~ 0.55-0.57), narrow (AL/AW ss 2.2), elliptical, with specimen (IRSN IG 26482, SL 8.2 mm) was extracted
narrow callus extending onto parietal and columellar from the shell and dissected. Preserved tissues lack pig-
regions of inner lip. Operculum oval, with terminal mentation. Foot short, truncated posteriorly, operculum
nucleus. Periostraeum thin, tightly adherent, transpar- missing, likely lost during fixation (opercular disk dis-
ent. Shell light hrown to rust-colored, with a characteris- tinct). Mantle cavity deep (LAV ~ 2), mantle edge did
tic whitish spiral band along shell periphery, whitish not cover head. Siphon short, very broad. Head small,
columellaand siphonal canal. with long, closely spaced tentacles, large, hrown eyes on
. . .
Page 48 THE NAUTILUS, Vol. 127, No. 2
very small lobes at tentacle bases. Disposition of mantle very similar to F. albozonata, and also has the whitish
cavityorgans typical for Buccinoidea. Ctenidium narrow, spiral band along the shell periphery that is present in
spanning % of mantle cavity, ospbradium equal in width F albozonata. As we have not found any material of
toctenidium, slightlyshorter. Hypobranchial gland with- F. albozonata from South Georgia, we cannot confirm the
out distinct folds. Rectum very short, broad. Proboscis presence oftliis taxon off South Georgia, nor its status as
mm
(Figure 14, pr) long, narrow, about 3.2 in length seniorsynonym ofM. nigropunctata (= M. antarctica)
(0.7 AL). Proboscis retractor muscles (Figures 13, 14, prr) Powell (1951: fig. K, 59) illustrated the radular denti-
verythin, paired, symmetrical, attached to rhynchodaeum tion of a specimen collected off South Georgia Island
(Figures 13-15, rhy) at mid-length. Salivary glands that he attributed to F. albozonata A reexamination of
(Figures 13, rsg, 14, 15, lsg) medium-sized, oval, fused voucher material (station 149) identified by Powell and
ventral to rhynchodaeum, covering nerve ring (Figure 15, deposited in the Natural History Museum (NI4MUK
nr) and mostofvalve ofLeiblein (Figure 15, vL). Salivary 1961499) revealed the specimens to be referable to
ducts (Figures 13, rsd, 14,15, lsd) very thick, running F.fulvicans (see belowfor further discussion).
alongboth sides ofanterior oesophagus. Valve of Leiblein Another species that Powell (1951) considered to be a
well defined, conical. Gland of Leiblein (Figures 13, 14, synonym ofF. albozonata is Lachesis australis, also from
gL) small, simple, tubular, colorless, joins esophagus Kerguelen. Two syntypes of L. australis were located
through a slightly constricted duct posteriorto nerve ring. in the Zoological Museum of Berlin (ZMB 59955)
Odontophore spans 2/3 of proboscis length. Subradular (Figures 11-12). One of the specimens (Figure 11)
cartillages fused along entire length. Radula equal to matches typical Falsimohnia albozonata, while the
odontophore in length. Radula (Figures 17-19) narrow, other (Figure 12) differs in havinga more slender shell
about 75-90 pm wide (1.6-1.8% of AL). Lateral teeth with a more elongated aperture and uniform colora-
with long base tapered toward the outer edge, with two tion, lacking the whitish band along the shell periphery
strong, curved cusps, the inner cusp slightly shorter, and siphonal canal. We examined a similar specimen
emanating from the inner half of the tooth. Rachidian from Crozet Islands (Figures 8-10) and found the radula
tooth with aV-shaped base nearly as long as wide, deeply (Figure 20) to be identical to that oftypical specimens of
notched anteriorly and with one strong, long cusp ema- F. albozonata (Figures 17-19). It is at present unclear
natingfrom posteriormidline of the tooth. whether die conchological differences are due to intra-
specificvariation, orwhetherthe two morphotypes repre-
Remarks: We did not examine the holotype of sent different species of Falsimohnia. In order to stabilize
Buccinum albozonatum, but studied several specimens the nomenclature, we here designate the specimen illus-
collected close to the type locality (Kerguelen). tratedin Figure 1 (ZMB 59955a) as lectotypeofLachesis
1
Conehologically they are very similar to the published australis Martens and Thiele, 1904. The remaining speci-
description (Watson, 1882) and subsequent illustra- men (Figure 12, ZMB 59955b) becomes a paraleetotype.
tions (Watson, 1886:pl. 13, fig. 7) ofthis species. We do As the lectotype has all the morphological features of
note, however, that all specimens we examined had a Falsimohnia albozonata, Lachesis australis Martens and
slightly different operculum. Watson (1886) stated that Thiele, 1904, is a junior subjective synonym ofBuccinum
“Operculum is intermediate in form between that of albozonatum Watson, 1882.
Buccinum andCominella for, asin the latter, thenucleus
;
is at the lower end, but it is not apical, but is within the Falsimohniafulvicans (Strebel, 1908)
edge towards the outer margin as in the former.” In the (Figures 21-27, 35-36)
specimenswe studied, most opereula are eroded tovary-
ing degrees (Figure 4), yet their general shape indicates Bela fulvicans Strebel, 1908: 15, Taf. 2, fig. 25 a-d;
that their nuclei are terminal, not subcentral. In other Melvill and Standen, 1912: 356; Powell, 1951: 56
respects the shells of the specimens examined are very (Burwood Bank), 59 (South Georgia); Zelaya, 2005:
similar to the figure published by Watson. The opereula 128, fig. 52 (figure erroneously labelled as Lorabela
of the samples we examined matched the illustration of pelseneeri); Engl, 2012: 181, pi. 73, fig. 7a-c.
the operculum ofF. albozonatum that was published by
Powell (1951: fig. N, 127).
Powell (1951:138) considered Falsimohnia albozonata Type Locality: South Georgia, Cumberland Bay, out-
to have a broad geographic range, and synonymized side Grytviken, 54°22' S, 36°27' W, 24-52 m (Swedish
Mangelia antarctica Martens and Pfeffer, 1886 (from South PolarExpedition, sta. 25). [Thecoordinatesprovided
South Georgia Island) and Lachesis? australis Martens on the printed label accompanying the specimen and in
and Thiele, 1903 (from Kerguelen Island). The name Strebel’s original description are likely erroneous, as they
Mangelia antarctica was unnecessary replacement name correspond to alocation on dry landclose to Grytviken.]
for Mangelia nigropunctata Martens, 1885 from South
Georgia (Zelaya, 2005). Type Material: Lectotype, SMNH Type 6303 (des-
We were not able to examine the type material of ignated by Engl, 2012: p. 181) (Figures 21-22).
Mangelia nigropunctata However, Martens and Pfeffer’s Paralectotypes: SMNH Type 1030 (st. 34, Cumberland
illustrations (1886:pl. 1, fig. 5) indicate that their taxon is Bay, 54°IP S, 36°18' W, 252G310 m) (Figures 24-26);
Y. I. Kantorand M.G. Harasewyeh, 2013 Page 49
Figures 21-32. Species ofFalsimohnia. 21-27. Falsimohnia ftilvicans (Strebel, 1908). 21-22. Leetotype, (SMNH Type-6303),
(SL 8.1 mm). 23. Paralectotype, (SMNH Type-6159). 24-25. Body of paralectotype (SMNII Type 1030) 26. penis tip of
NHMUK
paralectotype in figures 24-25. 27. Specimen from South Georgia identified by Powell as Falsimohnia albozonata,
1961499, (SL 7.6 mm). Figures 28-32. Falsimohnia minor (Strebel, 1908). Syntypes (SMNH Type-1057). 28. (SL 5.6 mm). 29.
(SL 5.8 mm). 30-32. (SL 6.5 mm). Left scale bar applies to figures 21,22, 27, right scale bar applies to figures 28-32. The 1mm
scaleliarappliestofigure 26.
Page 50 THE NAUTILUS, Vol. 127, No. 2
Figures 33-38. Radulae. 33-34. Falsimohnia minor (Strebel, 1908), radula from syntype in figure 29. 35-36. F fulvicans
(Strebel, 1908), radula from paralectotype in figures 24-25. (SMNH Type 1030). 37-38. Strebelona notophila (Strebel, 1908),
radula from holotype. Figures 44-45 (SMNHType-1064). Seale Bars = 10 pm.
?
Y. I. Kantorand M.G. Harasewyeh, 2013 Page 51
SMNH Type 6159 (st. 95, offAstrolabe Island, 64°09' S, F fulvicans indicates that they were misidentified as
58°17' W, 95 m) (Figure 23). F albozonata by Powell. Discovery station 149 is very
closetoCumberland Bay, the type localityofF. fulvicans
Description (based on intact shell of lectotype): and the depth is comparable to that from which a,
Shell medium-sized (to 8.1 mm), strong, thick, narrowly paralectotype ofF fulvicans was collected. In a survey of
fusiform, with moderatelyconvexwhorls andattenuated, the Mollusca ofthe Burwood Bank, Melvill and Standen
narrow, siphonal canal. Protoconch eroded, rounded, (1912:356) reported a single “imperfect, bleached speci-
paucispiral. Whorls with narrow and slightly concave men” that they tentativelyidentified as Belafulvicans.
subsutural ramp, evenly convex along periphery. Axial
sculpture ol narrow, weakly sinuate and weakly Distribution: South Georgia, and questionably
prosocline ribs, extending from suture to suture on spire, Burwood Bank.
becoming obsolete on periphery oflast whorl (~ 15 ribs
on penultimate and lastwhorls). Spiral sculptureofsharp, Falsimohnia minor Strebeh 1908
~
raised spiral cords. Cords (7-9 on spire whorls, 18 on (Figures 28-34)
last whorl) broadly spaced adapically, with interven-
ing spaces 1-2 times broader than cords. Cords become Bela anderssoni var. minor Strebel, 1908: 15; Powell,
broader than intervening spaces along shell periph- 1951:59; Engl, 2012:181, pi. 73, fig. 6a.
ery, indistinct on siphonal canal. Aperture large (AL/SL Typhlodaphneinnocentia Dell, 1990: AldeaandTroneoso,
« 0.53), elliptical (AL/AW « 2.0), with callus extending 2008: 82, fig. 64; AldeaandTroneoso, 2010: 144-145,
alongparietal region andcolumella. Operculum oval,with fig. 157.
terminal nucleus, shifted to left. Periostracum beige,
tightly adhering. Shell beige, lighteron siphonal canal. Belapolysarcavar.minorLocard, 1897,Belapyrrhogramma
var. minor Locard, 1897, and Bela anderssoni var.
Gross Anatomy: Animal of the paralectotype with a minor? Strebel, 1908, were all proposed as taxa of sub-
broken shell (Figures 24-26, <$) was dissected. Anatomy specific rank (ICZN, 1999: Article 45.6.4). In our view,
similar to Falsimohnia albozonata in most regards. Eyes both Bela polysarca var. minor Locard 1897 and Bela
,
large. Penis long, about the length of mantle cavity, dor- pyrrhogrammavar. minorLocard, 1897are nomina nuda
,
soventrally compressed, blunt distally with long but nar- as neither name is accompanied by a description or defi-
rowseminalpapillashiftedposteriorly, situated on dorsal nition of the taxon, nor by an indication (ICZN, 1999:
edge of penis (Figure 26). Proboscis of moderate length, Article 12). As nomina nuda these names are not avail-
,
cylindrical, taperingdistally. Radula (Figures 35-36) nar- able names and do not enter into homonomy (ICZN,
row (~60 pm wide), lateral teeth with broad base, elon- 1999: Article 54).
gated andweakly recurved outer edge, two strongcusps,
inner cusp shorter, emanating from middle and inner Type Locality: South GeorgiaIsland,outerCumberland
portions ofbase. Central tooth with nearly square basal Bay, 54°11' S, 36°18' W, 252-310 m, Swedischen
plate, its anterior edge V-shaped with indentation accom- Siidpolar-Expedition, sta. 34.
modatingsingle medial cusp emergingfrom rounderpos-
terior edge ofanteriorly adjacent tooth. Lateral edges of Type Material: 3 syntypes, SMNH Type-1057.
basal plate ofcentral tooth with thickened ridges parallel
tocentral cusp, possiblyvestiges oflateral cusps. Stomach Description: Shell small (to 6.5 mm), strong, moder-
with longposteriormixingarea. ately thick, with convex whorls and short broad canal,
with shallow but distinct notch. Protoconch bulbous,
Remarks: Thespecies is ratherdistinct, resemblingthe eroded on all specimens. Profile of whorls between
shell outline ofProbuccinumcostatum (Thiele, 1912), but suture and shoulder slightly concave. Axial sculpture of
differing from that taxon in having more numerous axial narrow, slightlysinuous, nearlyorthoeline ribs (14-15 on
ribs on the shell, and a different radula. In Probuccinum penultimate and last whorls), extending from suture to
the radula is typical buccinulid, with broad tricuspid suture on spire and suture to siphonal canal on last
central teeth and tricuspid lateral teeth that lack an elon- whorl. Spiral sculpture of low, sometimes indistinct,
gated outer basal plate. Falsimohniafulvicans appears to closely spaced spiral cords that are broader than inter-
be rare, as the only confirmed record since the origi- vening spaces. Aperture large (AL/SL = 0.54-0.61),
nal description is that of Zelaya (2005). The radula of moderately broad (AL/AW« 1.9), elliptical, inner lip
F.fulvicans is very similar to that of F. albozonata as is with narrow callus on columellar and parietal portions.
its penis morphology, both providing support for the Operculum oval, transluscent, with terminal nucleus,
transfer ofthis species to the genus Falsimohnia. shifted to left. Periostracum tightly adhering, beige to
In his discussion of F. albozonata Powell (1951:138) yellowish. Shell orange tobrownish beige, siphonal canal
,
considered the range of this species to include South andcolumellalighter, oftenwhitish. Radula (Figures 33-
Georgia Island. Two specimens from Discovery station 34) [narrow (~ 55 pm wide, 1.7% ofAL),] short. Lateral
149 that had been identified by Powell as F. albozonata teethwith longbasal platewithelongatedouteredge and
(NHMUK 1961499) were examined (Figure 27). The two strong, curved cusps, inner one slightly shorter.
similarity of these specimens to the lectotype of Basal plate ofcentral tooth nearly square, with shallow
Page 52 THE NAUTILUS, Vol. 127, No. 2
notcli in anterior margin to accommodate cusp or adja- Distribution: SouthGeorgia, Bellinghausen Sea,PeterI
cent tooth, and one strong, long medial cusp emanating Island, 90-310 m.
from posterior edge. Small denticle on left side ofcusp.
Remarks: Strebel (1908) attributedonlyvarietal status Falsimohnia anderssoni (Strebel, 1908)
to this taxon. We regard Falsimophnia minor to be a (Figures 39-41)
distinct species, differing from F. andersssoni in having
more pronounced, wider and more broadly spaced axial Bela anderssoni Strebel, 1908: 14—15, Taf. 2, fig. 24 a-d;
ribs, and far less distinct spiral sculpture. The morphol- Mellvill and Standen, 1912:355; Powell, 1951: 56;
ogy of the radula, which is nearly identical to that of Engl, 2012:180-181, pi. 73, fig. 6b.
F. albozonata and F. fulvicans, confirms the placement Type Locality: SE of Seymour Island, 64°20'S,
of this species in the bueeinulid genus Falsimohnia.
Conehologieally, F. minor resembles some speci- 56°38'W, 150 m, Swedischen Siidpolar-Expedition, sta. 5.
mens of Chlanidotella modesta (Martens, 1885) from Holotype: SMNH Type-1063.
South Georgia, but differs in its smaller shell size and
radular morphology. In C. modesta the lateral teeth have Description: Shell small (to 9.4 mm), fusiform, thick,
4-5 cusps and the central tooth bears three distinct with evenly rounded, convex whorls and short broad
cusps of similar size (Powell, 1951: fig. L80; unpub- canal. Protoconch bulbous, eroded. Axial sculpture of
lished observations). low, very narrow, slightlysinuous ribs (19 on penultimate
Figures39-45. SpeciesofFalsimohnia andStrebela newgenus.39—43. Falsimohniaanderssoni (Strebel, 1908). 39—41. Holotype
(SMNH Type-1063) (SL 9.4 mm). 42-43. USNM 870245, offElephant Island, South Shetland Islands, 220-240 m. 44-45. Type
species of Strebela newgenus: Bela notophila Strebel, 1908, holotype, (SMNH Type-1064), (SL8.1 mm), (radulaextracted).