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Actual and Alleged Freshwater Mussels (Mollusca: Bivalvia: Unionoida) from Madagascar and the Mascarenes, with Description of a New Genus, Germainaia


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Madagascar is widely recognized as a biodiversity hotspot, but the freshwater bivalves have received only limited recent attention. Based upon examination of records from 15 major museums and a literature review, at least nine species of freshwater mussels (Mollusca: Bivalvia: Unionoida) have been reported from either Madagascar or the Mascarene Islands (specifically, Reunion or Mauritius) in the Indian Ocean, east of Africa. The quality of the data, however, is generally poor. Seven of those species records are regarded as either erroneous reports of taxa known from other regions or as nomina dubia. No records from the Mascarenes are considered to be valid. The two remaining species, Etheria elliptica Lamarck 1807 and Unio geayi Germain 1911 (= Coelatura geayi) are both from Madagascar, and the latter is discussed in the context of two alternative hypotheses for the origin of the family Unionidae, nicknamed “Out of Africa” and “Into Africa.” Germainaia gen. nov. is introduced for Unio geayi to emphasize the distinction of that species from other Afrotropical freshwater mussel lineages. The possibility that Germainaia may represent the Hyriidae in Madagascar is discussed, but the new genus is left incertae sedis at the family-level in the absence of complete data. New taxon: Germainaia Graf and Cummings
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Freshwater mussels, or naiads (Bivalvia: Unionoida),
represent an ancient lineage known from all large, conti-
nental landmasses except Antarctica (Graf and Cummings
2006b, 2007b). This includes the island of Madagascar, but
the Malagasy mussel fauna is not well known. The wide-
spread Etheria elliptica Lamarck 1807 (Etheriidae) and
four endemic species of Coelatura (Unionidae) have been
reported from either Madagascar or the nearby Mascarene
islands of Mauritius and Reunion (Haas, 1969a; Fischer-
Piette and Vukadinovic, 1973; Daget, 1998), in addition
to other erroneous reports of species currently known to
reside elsewhere. These data are at odds with prevailing
hypotheses of unionoid biogeography, and the objectives
of this article are to reexamine and vet the available speci-
men records and to update the taxonomy of the unionoid
species reported from those landmasses in the southwest-
ern Indian Ocean.
Madagascar is a continental island of 587,000 km2
(4th largest on Earth, excluding Australia) located in the
southwestern Indian Ocean, less than 1000 km from the
southeastern coast of Africa but no closer than 400 km.
The island is almost entirely tropical, extending from -12°
to -25.6° latitude. Thieme et al. (2005) and Abell et al.
(2008) divided the subcontinent into five ecoregions based
upon fish diversity and other ecological patterns, but the
primary, east-west physiographic division is created by a
long backbone of highlands running parallel to the eastern
coast (Fig. 1). Precipitation is generally greatest east of the
mountains, up to 350 mm monthly. As a result, rivers in the
eastern lowlands flow year-round (Aldegheri, 1972). West
of the mountains, the climate is drier, with a precipitation
gradient decreasing from north (2500 mm yr-1) to south (<
500 mm yr-1). Compared to elsewhere on the island, the
streams of northwestern Madagascar have more constant
flow regimes, nearly neutral pH, higher levels of dissolved
carbonates, and a diverse fish fauna with 71 native species
(Sparks, 2005). Thus, this region may be most suitable for
sustaining freshwater mussels, given the aquatic mollusks’
need to maintain a calcareous shell and dependence upon
fishes as hosts for parasitic larvae (Wächtler et al., 2001).
Unfortunately, the freshwater bivalves of Madagascar
have been little studied, despite the intersection of a glo-
bally imperiled taxon (Bogan 1993, Lydeard et al., 2004;
Strayer, 2006) with a widely recognized biodiversity
hotspot (Myers et al., 2000; Goodman and Benstead, 2003;
Kremen et al., 2008).
Actual and alleged freshwater mussels (Mollusca: Bivalvia: Unionoida) from
Madagascar and the Mascarenes, with description of a new genus, Germainaia
Academy of Natural Sciences, 1900 Benjamin Franklin Parkway, Philadelphia PA 19103 USA. Current Address: University of
Alabama, MH Bryant Hall, Box 870345, Tuscaloosa AL 35487 USA
Illinois Natural History Survey, University of Illinois, 1816 S. Oak Street, Champaign IL 61820 USA
ABSTRACT.—Madagascar is widely recognized as a biodiversity hotspot, but the freshwater bivalves have received only
limited recent attention. Based upon examination of records from 15 major museums and a literature review, at least nine
species of freshwater mussels (Mollusca: Bivalvia: Unionoida) have been reported from either Madagascar or the Mascarene
Islands (specifically, Reunion or Mauritius) in the Indian Ocean, east of Africa. The quality of the data, however, is generally
poor. Seven of those species records are regarded as either erroneous reports of taxa known from other regions or as nomina
dubia. No records from the Mascarenes are considered to be valid. The two remaining species, Etheria elliptica Lamarck 1807
and Unio geayi Germain 1911 (= Coelatura geayi) are both from Madagascar, and the latter is discussed in the context of two
alternative hypotheses for the origin of the family Unionidae, nicknamed “Out of Africa” and “Into Africa.” Germainaia gen.
nov. is introduced for Unio geayi to emphasize the distinction of that species from other Afrotropical freshwater mussel lineages.
The possibility that Germainaia may represent the Hyriidae in Madagascar is discussed, but the new genus is left incertae sedis
at the family-level in the absence of complete data.
New taxon: Germainaia Graf and Cummings
Key words: Mauritius, Reunion, Unionidae, Etheriidae, biogeography
ISSN 0097-3157
The Mascarene Islands are located from 690 to 1260
km east of Madagascar. The three main islands of the group
(in addition to several smaller ones) from west to east, are
Reunion (formerly Bourbon Island), Mauritius (formerly
Île de France), and Rodrigues. The Mascarenes, in con-
trast to cratonic Madagascar, are oceanic islands formed
by volcanism. The islands were never part of Gondwana
(forming only 10 million years ago), and thus have lacked
direct terrestrial/freshwater connections to Madagascar or
any other continental body. There are a number of high-
gradient streams on the islands, but they are all less than 40
km in length (Abell and Brown, 2005).
As students of the evolution and diversity of the
Afrotropical freshwater mussel fauna, we have been
intrigued by the hypothesized presence of the family
Unionidae on Madagascar and the Mascarene Islands (Graf
and Cummings, 2007b). Although it has been suggested,
following inferences from phylogenetic topology, that
unionids may have arisen on Africa or elsewhere on
Gondwana (Hoeh et al., 2002) and then spread “Out of
Africa,” other evidence suggests that the ancestor of the
extant lineages occurred on the northern continents and
then subsequently dispersed south and diversified as
fragments of Gondwana collided with Eurasia (Kat, 1987;
Graf, 2000). This “Into Africa” hypothesis is derived from
the fossil and modern distributions of unionoid families.
Ignoring the dubious Cretaceous species from northwestern
Africa questionably assigned to the Unionidae by Mongin
(1963, 1977), unionid fossils are unknown from any of the
former Gondwanan continents (Antarctica, South America,
Africa, India, Australasia, and Madagascar) until the
Miocene (Haas, 1969b; Van Damme, 1984). The Recent
Unionidae is known only from North America, Eurasia
(including India), Africa, New Guinea and Madagascar
(Graf and Cummings, 2007b; Bogan and Roe, 2008).
The presence of unionid species on India, Africa and
New Guinea — all formerly parts of Gondwana — can
be explained by Eurasian lineages invading from the
north. Madagascar, however, has been isolated from the
northern continents since Pangaea disintegrated before the
end of the Jurassic (Scotese et al., 1988; Sanmartín and
Ronquist, 2004). Thus, the presence of three species of the
Fig. 1. Maps showing the location of Madagascar and the Mascarene Islands in the Indian Ocean and the reported collection localities of
Etheria elliptica in northwestern Madagascar. The darker shaded region on the background map shows the entire distribution of Etheria
elliptica on Africa and Madagascar. The inset shows Madagascar in detail. Thieme et al. (2005) divided the island into five freshwater
ecoregions based upon fish distributions. The Northwestern region (NW) includes the westward draining rivers, from the Mahavavy du
Sud to the northern tip of the island. The remaining western rivers, from the Andranomavo to the Onilahy, comprise the Western region
(W). Southward running streams are grouped as the Southern region (S). The upper reaches of the eastern flowing rivers comprise the
Eastern Highlands region (EH), and their lowest stretches are grouped as the Eastern Lowlands (EL) as a narrow strip of land along the
eastern coast.
otherwise African unionid genus Coelatura C. geayi
(Germain 1911), C. madagascariensis (Sganzin 1841) and
C. malgachensis (Germain 1911) — on Madagascar (Haas,
1969a; Fischer-Piette and Vukadinovic, 1973; Daget, 1998)
presents a challenge to the “Into Africa” hypothesis.
Moreover, the occurrence of Coelatura cariei
(Germain 1919) and other species on the oceanic Mascarene
Islands (Barré et al., 1982; Daget, 1998) is contrary to
what is known of the life history and dispersal ability of
the Unionidae. Freshwater mussels of the order Unionoida
possess larvae with an obligate parasitic stage that infects
freshwater fishes (Wächtler et al., 2001). While the ecol-
ogy of this interaction is best understood for the freshwater
mussels of North America (Watters, 1994; Barnhart et al.,
2008), few observations are available for Afrotropical spe-
cies. Nevertheless, the observed generality of larval para-
sitism across all six unionoid families (Hoeh et al., 2002;
Graf and Cummings, 2006b) supports the presumption of
its occurrence in all species, except for a few known de-
rived exceptions among Neotropical species of the hyriid
genus Rhipidodonta and the African unionid Grandidieria
burtoni (Woodward 1859) (Kondo, 1990; Simone, 2006).
Freshwater mussels depend upon fishes for their dispersal,
and as a result they are incapable of breeching terrestrial
and oceanic barriers between river basins (van der Schalie,
1945; Graf, 2002). This characteristic makes freshwater
mussels useful for biogeographic studies: disjunctions
among taxa are strong evidence for past connections among
isolated water bodies. It is significant then that the reports
of unionid species on the Mascarene Islands represent
only the second example of freshwater mussels recently
reported from oceanic islands so distant from a continental
mass the other being Margaritifera (Margaritiferidae)
on Iceland, 850 km from Europe (Ziuganov et al., 1994).
Other freshwater bivalves of the families Sphaeriidae
and Corbiculidae (Veneroida) are known from Madagascar
and the Mascarenes, in addition to estuarine marine taxa
(Daget, 1998). The species of these freshwater families are
well known for their dispersal abilities and often-cosmo-
politan distributions, so they do not offer the same interest-
ing biogeographical problems as freshwater mussels. We
have not endeavored to explore those taxa further.
Our approach to addressing the distributions of fresh-
water mussels on Madagascar and the Mascarene Islands
was to reevaluate the original specimen records that form
their basis. This research was undertaken as part of a larger
project to revise the unionoid families of the southern,
Gondwanan continents: Australia, South America, India,
Africa and Madagascar. Southern-continent freshwater
mussel specimens from fifteen major museum collec-
tions in the USA, Europe and Australia have been exam-
ined to-date. However, only five of these had specimens
from Madagascar or the Mascarenes: the Academy of
Natural Sciences of Philadelphia, Pennsylvania (ANSP),
University of Michigan Museum of Zoology, Ann Arbor
(UMMZ), The (British) Natural History Museum, London
(BMNH), Museum für Naturkunde, Berlin (ZMB), and
Muséum National d’Histoire Naturelle, Paris (MNHN).
In addition, we found literature references to specimens
we have not studied in the Musée d’Histoire Naturelle,
Geneva (MHNG) and the Zoological Museum, University
of Copenhagen (ZMUC).
The specimen lots examined, including associ-
ated labels, were digitally photographed and incorpo-
rated with literature references into the MUSSEL Project
Database (MUSSELpdb) following the methods of Graf
and Cummings (2006a, 2007a). The MUSSELpdb was
developed in FileMaker Pro (FileMaker Inc., Santa Clara,
CA;, and a schematic of our
data model is available on the MUSSEL Project Web Site
( Those specimen and lit-
erature references form the basis of our revisions of the
species in question.
As far as we can determine, we have located and re-
ported on every primary literature record to the freshwa-
ter mussel species regarded as endemic to the study area.
For the taxa erroneously reported from Madagascar and
the Mascarene Islands, we have not endeavored to provide
complete synonymies, as they would be cumbersome for
the objectives of this article. Our intention is merely to
indicate the past taxonomic combinations of the specific
nomina discussed and to list helpful references to other
systematic works and figures. This is also true for the
widespread Etheria elliptica, a more complete synonymy
of which can be found in the references cited under that
As of October 2008, the MUSSEL Project Database
holds 16,755 specimen records, 4224 of which are from
the Afrotropical region, and 14 were labeled as from
Madagascar or the Mascarene Islands. In all, we have
found reports of nine species from specimen records or the
literature (Table 1), but only one species on Madagascar,
the widespread Etheria elliptica, is supported by multiple
collection records. A second Malagasy species, described
as Unio geayi Germain 1911, is known from only a sin-
gle lot of 2 + ½ specimens. Recent arrangements have
placed the latter in the otherwise African genus Coelatura
(Fischer-Piette and Vukadinovic, 1973; Daget, 1998), but
it should be regarded in its own genus, Germainaia gen.
Table 1. Freshwater Mussel Species Reported from Madagascar and the Mascarene Islands.
Nominal Taxon Island Status
Etheria elliptica Lamarck 1807 Madagascar valid in Etheriidae (Africa & Madagascar)
Unio geayi Germain 1911 Madagascar valid as Germainaia geayi, family incertae sedis
Unio madagascariensis Sganzin 1841 Madagascar nomen dubium
Unio malgachensis Germain 1911 Madagascar nomen dubium
Nodularia cariei Germain 1919 Reunion = Coelatura aegyptiaca (Cailliaud, 1827)
(West Africa & the Nile Basin)
Unio sinuata Lamarck 1819 Reunion = Margaritifera auricularia (Spengler 1793)
(Western Europe & Morocco)
Unio brevialis Lamarck 1819 Mauritius = Potomida littoralis (Cuvier 1798)
Unio mauritianus Lea 1859 Mauritius = Simpsonella purpurea (Valenciennes 1821)
Unio fluctiger Lea 1859 Mauritius = Diplodon fluctiger (South America)
nov. (described below), given its distinctiveness from other
known Afrotropical species. We consider the seven other
reported species from Madagascar and the Mascarene
Islands dubious or erroneous.
Class Bivalvia
Subclass Palaeoheterodonta
Order Unionoida
Family ETHERIIDAE s.s.
Genus Etheria Lamarck, 1807
Etheria elliptica Lamarck
Figure 2
Etheria elliptica Lamarck, 1807. Ann. Mus. Hist. Nat. 10:
401, pl. 29; pl 31, fig. 1; 1819, Hist. Natur. Anim. sans
Vert. 6: 99. Holotype MNHN 21209. Published local-
ity: “... de la mer des Indes...” — Pilsbry & Bequaert,
1927, Bull. Amer. Mus. Nat. Hist. 53: 449, pl. 46, figs.
1-1a; pl. 30, figs. 2-2a. — Pain & Woodward, 1961, J.
Conch. 25: 3. — Haas, 1936, Abh. Senck. Naturf. Ges.
431: 101; 1969a, Superf. Unionacea: 602. — Fischer-
Piette & Vukadinovic, 1973, Malacologia 12: 369.
— Daget, 1998, Cat. Moll. Bivalves d’Eau Douce
Africains: 159. — Graf & Cummings, 2007b, J. Moll.
Stud. 73: 313.
Etheria trigonula Lamarck, 1807. Ann. Mus. Hist. Nat. 10:
403, pl. 30; pl. 31, fig. 2; (1819), Hist. Natur. Anim.
sans Vert. 6: 99. Holotype MNHN 21210. Published
locality: “On prétend que cette espèce habite dans les
mêmes mers que la précédente [= E. elliptica].”
Etheria semilunata Lamarck, 1807. Ann. Mus. Hist. Nat.
10: 404, pl. 32, figs. 1-2; (1819), Hist. Natur. Anim.
sans Vert. 6: 100. Holotype MHNG (Madagascar) fide
Daget (1998: 159).
Etheria transversa Lamarck, 1807. Ann. Mus. Hist. Nat.
10: 406, pl. 32, figs. 3-4; (1819), Hist. Natur. Anim.
sans Vert. 6: 100. Holotype MHNG (Madagascar) fide
Daget (1998: 159).
Ætheria elliptica Lamarck. — Germain, 1907, Bull. Mus.
Hist. Nat. 13: 225; (1918), Bull. Mus. Hist. Nat. 24:
35. — Fischer-Piette, 1945, Bull. Mus. Hist. Nat. 17:
Material examined.
Unknown locality: MNHN 21209 (1 spec.); MNHN 21210
(1 spec.).
Madagascar [without more specific locality data]: UMMZ
112672 (2 spec.); ZMB 109101 (2 spec.); ZMB
111979 (3 spec.).
Ambongo [Mahajanga]: BMNH 20080837 (1 spec.) [This
specimen was collected by Perrier de la Bathie, who
also collected MNHN 21214 and other specimens
from the Mahavavy River (Germain, 1907), both
located in the District d’Ambongo of Mahajanga
Province (Lloyd, 1850).]
Sahondra River [Mahajanga]: MNHN 21215, 21214 (2
lots, 1 spec. each).
Betsiaka River [Antsiranana]: MNHN 21216 (2 spec.).
Diagnosis.Etheria elliptica is easily distinguished
from all other Malagasy freshwater bivalves by its large
size, irregular shape and cementing habit.
Distribution.Etheria elliptica is widespread in the
Afrotropics, including West Africa, the Nile and Congo
Basins, southward to the Cunene River in Angola (Graf
and Cummings, 2006a, 2007a-b). In Madagascar, the spe-
cies has only been reported from a few localities in the
Northwestern and Western ecoregions on the island (Fig.
1). In addition to the records listed above, Germain (1907)
discussed specimens from the Mahavavy du Sud Basin, in-
cluding the Androtsy River (Fischer-Piette, 1945; Fischer-
Piette and Vukadinovic, 1973), and the type locality re-
ported for each of Etheria semilunata and E. transversa
was given as Madagascar (specimens not seen).
Remarks.E. elliptica is the only freshwater mus-
sel species reported from Madagascar based upon multiple
collections. Specimens, however, are still relatively rare,
with only seven different specimen lots located in our mu-
seum survey (not counting those published records we did
not locate). The presence of E. elliptica on both Africa and
Madagascar has interesting biogeographical implications,
discussed below.
Family incertae sedis
Germainaia, new genus
Description.— Characters of the type species, known
only from the type series from Madagascar. Elongate, cy-
lindrical valves with unsculptured, brown periostracum.
Umbo/juvenile sculpture unknown (eroded in all speci-
mens). Hinge teeth weakly developed. Soft-anatomy un-
Type species.Unio (Nodularia) geayi Germain 1911.
Etymology.— This freshwater mussel (i.e., naiad)
genus is named for Louis Germain (b. 1878, d. 1942), who
served as both Professeur de Malacologie and Directeur
during his tenure at the Muséum National d’Histoire
Naturelle in Paris (Fischer-Piette, 1947), and who also de-
scribed the type species.
Remarks. A new genus for Unio geayi Germain
1911 is a phylogenetic hypothesis, formalized by the rules
Fig. 2. Etheria elliptica Lamarck 1807. MNHN 21215. Sahondra River, Mahajanga, Madagascar.
of binomial nomenclature. Historically, this species has
been variously treated in the genera Unio, Nodularia and
Coelatura. During the earliest part of the 20th century (e.g.,
Simpson, 1900), the former two genera were far more
inclusive than they are currently applied. Today, Unio
and Nodularia refer to restricted groups of species in the
Western and Eastern Palearctic, respectively (Graf, 2007;
Graf and Cummings, 2007b). The use of Coelatura in
this instance, a widespread and morphologically variable
African genus, has generally been by default and without
confidence (Simpson, 1914; Haas, 1969a; Daget, 1998;
Graf and Cummings, 2007b), except that Fischer-Piette
and Vukadinovic (1973), without justification, restricted
the species to a specific subgenus, C. (Zairia) geayi. Zairia
is otherwise known from western Africa (Haas, 1969a). By
placing Unio geayi Germain 1911 into any one of these
genera, we would be making a phylogenetic hypothesis.
However, the available data and our hypotheses about the
relationships among the Afrotropical freshwater mussels
(discussed below) are inconsistent with the phylogenies
congruent with those traditional arrangements (e.g., that
the African species of Coelatura plus Unio geayi Germain
1911 form an exclusive clade).
We hypothesize that Unio geayi Germain 1911 is phy-
logenetically distinct from the African Coelatura, although
the available data are insufficient to suggest an unambigu-
ous sister group for this species. Rather than leave it with-
out a genus, we have opted to call the species Germainaia
geayi to formalize this hypothesis. As discussed below, the
available data are, in fact, insufficient to confidently place
G. geayi into a family, its shell morphology consistent with
both the Unionidae and the Hyriidae. Thus, we have treated
Germainaia as incertae sedis at the family-group level.
Germainaia geayi (Germain)
Figure 3
Unio (Nodularia) geayi Germain, 1911. Bull. Mus. Hist.
Nat. 17: 137, pl. 1, figs. 1-2, 6-7. Lectotype (here sel-
ected) MNHN 1704 (Madagascar). — Haas, 1936,
Abh. Senck. Naturf. Ges. 431: 90.
Nodularia (Cælatura) [sic] geayi (Germain). — Simpson,
1914, Descr. Cat. Naiades: 1033.
Nodularia geayi (Germain). — Germain, 1918, Bull. Mus.
Hist. Nat. 24: 36.
Caelatura [sic] geayi (Germain) [in part]. — Haas, 1969a,
Superf. Unionacea: 187.
Caelatura [sic] (Zairia) geayi (Germain). — Fischer-Piette
& Vukadinovic, 1973, Malacologia 12: 368.
Coelatura geayi (Germain). — Daget, 1998, Cat. Moll.
Bivalves d’Eau Douce Africains: 51. Graf &
Cummings, 2007b, J. Moll. Stud. 73: 309.
Material examined. Madagascar [without more
specific locality data]: MNHN 1704 (1 spec.), MNHN
21211 (2 spec.).
Diagnosis. Germainaia geayi can be distin-
guished from all other bivalve species thought to occur on
Madagascar by its dark brown periostracum and weakly
developed schizodont hinge dentition.
Distribution.— The species is known only from the
vague type locality, Madagascar.
Remarks. The hypothesized phylogenetic rela-
tionships of Germainaia geayi have interesting biogeo-
graphic and evolutionary implications for the entire Order
Unionoida, as discussed below.
Dubious Species and Those Erroneously
Attributed to Madagascar or the Mascarene Islands
Unio madagascariensis Sganzin” nomen dubium
Unio madagascariensis Sganzin, 1841. Mém. Soc. Hist. Nat.
Strasbourg 3: 8. Type material unknown. Published
locality: “...elle se trouve assez abondamment dans
le Mahoupa, rivière située près de Tamatave, île de
Madagascar.”— Simpson, 1900, Proc. U.S. Nat. Mus.
22: 862; 1914, Desc. Cat. Naiades: 1193. — Germain,
1907, Bull. Mus. Hist. Nat. 13: 227; 1911, Bull. Mus.
Hist. Nat. 17: 137; 1918, Bull. Mus. Hist. Nat. 24:
37. — Kobelt, 1910, Abh. Senck. Naturf. Ges. 32:
92. — Haas, 1936, Abh. Senck. Naturf. Ges. 431: 89.
— Fischer-Piette & Vukadinovic, 1973, Malacologia
12: 368.
Caelatura [sic] madagascariensis (Sganzin). Haas,
1969a, Superf. Unionacea: 187.
Coelatura madagascariensis (Sganzin). — Daget, 1998,
Cat. Moll. Bivalves d’Eau Douce Africains: 62.
Graf & Cummings, 2007b, J. Moll. Stud. 73: 309.
Material examined.— None. Known only from the
original description.
Distribution. The reported type locality is the
Mahoupa River, near Tamatave, Madagascar. Tamatave
is known to be near the Ivondro River, whereas Tintingue
was near the Mahoupa (Barbié du Bocage, 1858). Both riv-
ers drain to the east.
Remarks.— This species was introduced by Sganzin
(1841) without a figure or adequate description (“...elle est
verte et d’une contexture très-fragile”). It has been treated
as valid (or questionably valid) in recent treatments of glo-
bal or Afrotropical unionoid diversity (Haas, 1969a; Daget,
1998; Graf and Cummings, 2007b), but Fischer-Piette and
Vukadinovic (1973) reported no freshwater bivalves from
the published locality on the eastern coast of Madagascar.
Unio malgachensis Germain” nomen dubium
Figure 4
Unio (— ?) malgachensis Germain, 1911. Bull. Mus. Hist.
Nat. 17: 139, pl. 1, figs. 3-5; 1918, Bull. Mus. Hist.
Nat. 24: 36. Holotype (by monotypy) MNHN 20832
(Madagascar; Geay!). Simpson, 1914, Desc. Cat.
Naiades: 719. — Haas, 1936, Abh. Senck. Naturf.
Ges. 431: 90.
Caelatura [sic] geayi (Germain) [in part]. — Haas, 1969a,
Superf. Unionacea: 187.
Caelatura [sic] (?) malgachensis (Germain). — Fischer-
Piette & Vukadinovic, 1973, Malacologia 12: 368.
Coelatura malgachensis (Germain). — Daget, 1998, Cat.
Moll. Bivalves d’Eau Douce Africains: 62. — Graf &
Cummings, 2007b, J. Moll. Stud. 73: 309.
Material Examined.—Madagascar [without more
specific locality data]: MNHN 20832(1 spec.).
Distribution.— Known only from the reported local-
ity of the type, Madagascar.
Remarks.— The sole specimen is <12 mm in length,
immature and unidentifiable. Haas (1969a) treated it as
merely a juvenile specimen of G. geayi.
Fig. 3. Germainaia geayi (Germain 1911). A. Lectotype MNHN 1704. Madagascar. B-C. Paralectotypes MNHN 21211. Same locality.
Caelatura [sic] cariei (Germain). — Haas, 1969a, Superf.
Unionacea: 187.
Nodularia carieri [sic] (Germain). — Barré et al., 1982,
Rev. Elev. Méd. Vét. pays Trop. 35: 36. Error for N.
cariei Germain.
Coelatura cariei (Germain). — Daget, 1998, Cat. Moll.
Bivalves d’Eau Douce Africains: 45. Graf &
Cummings, 2007b, J. Moll. Stud. 73: 309.
Material examined.— None. Known only from the
original description.
Distribution.— Reported from Reunion Island.
Remarks.As suggested previously by Haas (1969a),
Germain’s figure of this species (1921: pl. 3, figs. 33-34)
matches Coelatura aegyptiaca from the Nile and West
Africa (Fig. 5) (Graf and Cummings, 2007a). We regard
this nominal species to be the result of a label mix-up and
not to be a distinct, valid species.
Margaritifera auricularia (Spengler)
Unio auricularius Spengler, 1793. Skr. Naturhist. Selsk.
3: 54. Lectotype (selected by Falkner, 1994) ZMUC
BIV-315 (Berlingen near Unterseen, Switzerland)
(Knudsen et al., 2003).
Unio sinuata Lamarck, 1819. Hist. Natur. Anim. sans Vert. 6:
70. Syntypes (4 spec.) MHNG (the Rhine, the Loire and
other rivers of continental Europe) fide Johnson (1953:
93). Sganzin, 1841, Mém. Soc. Hist. Nat. Strasbourg
3: 8. — Germain, 1911, Bull. Mus. Hist. Nat. 17: 137.
Pseudunio sinuatus (Lamarck). — Haas, 1910, Nachr. Bl.
Dtsch. Malak. Ges. 42: 183.
Fig. 4. Unio malgachensis Germain 1911. MNHN 20832.
Madagascar. Scale bar equals 5 mm.
Nodularia cariei Germain”
Subjective junior synonym of Coelatura aegyptiaca
(Cailliaud 1827)
Figure 5
Nodularia (Cælatura) [sic] cariei Germain, 1919. Bull.
Mus. Hist. Nat. 25: 122; 1921, Faun. Malac. Terr.
et Fluv. Iles Mascareignes: 403, pl. 3, figs. 33-34.
Holotype (monotypy) figured specimen, presum-
ably MNHN, not found. Published locality: “Île de
la Réunion: Plaine des Cafres.” — Haas, 1936, Abh.
Senck. Naturf. Ges. 431: 90.
Fig. 5. Comparison of the umbo structure of Nodularia cariei with
Coelatura aegyptiaca. A. Reproduction of the original figure of
the lectotype of N. cariei (Germain, 1921: pl. 3, figs. 33-34). B. C.
aegyptiaca. UMMZ 232490. Egypt. Scale bar equals 1 cm.
Moll. Stud. 73: 309.
Material examined.—“Mauritius”: MNHN 21212 (1
Distribution. Circum-Mediterranean; from the
Maghreb in northern Africa, and southern Europe to the
Levant. The erroneous type locality reported for the junior
synonym Unio brevialis Lamarck 1819 is the Île de France
(= Mauritius).
Remarks.— The lectotype of U. brevialis is un-
doubtedly the Palearctic species recognized as Potomida
littoralis. Lamarck, however, introduced enough confusion
Margaritana sinuata (Lamarck). — Ortmann, 1912, Ann.
Carnegie Mus. 8: 232.
Margaritana auricularia (Spengler). — Germain, 1931,
Faune de France 22: 718
Margaritifera auricularia (Spengler). — Haas, 1940, Zool.
Ser. Field Mus. Nat. Hist. 24: 119; Daget, 1998, Cat.
Moll. Bivalves d’Eau Douce Africains: 16. — Graf &
Cummings, 2007b, J. Moll. Stud. 73: 312.
Margaritifera (Pseudunio) auricularia (Spengler).
Haas, 1969a, Superf. Unionacea: 13.
Pseudunio auricularia (Spengler). Smith in Bauer &
Wächtler, 2001, Ecol. Evol. Unionoida: 42.
Material examined.— None.
Distribution. Mediterranean southwestern Europe
and the Maghreb of northern Africa. Unio sinuata Lamarck,
1819 was erroneously reported by Sganzin (1841) from
Reunion Island.
Remarks.— According to Sganzin (1841: 9), “Cette
mulette [Unio sinuata Lamarck], qui m’a été donnée par M.
Fabert, chef de bataillon d’infanterie, comme se trouvant à
Saint-Paul, île Bourbon, me paraît douteuse, et je crains
que cet officier, qui recevait souvent des envois de l’Inde,
n’ait confondu les pays.” As even Sganzin (and everyone
since) did not recognize this record from Reunion Island, it
must be considered erroneous.
Potomida littoralis (Cuvier)
Figure 6
Unio littoralis Cuvier, 1798. Tab. Elem. Hist. Nat. Anim.:
425. Syntypes (6 spec.) MHNG (France, common
in the Seine) fide Johnson (1953: 91). Lamarck,
1801, Sys. Anim. sans Vert.: 114; 1819, Hist. Natur.
Anim. sans Vert. 6: 76.
Unio brevialis Lamarck, 1819. Hist. Natur. Anim. sans
Vert.: 73. Lectotype (here selected; listed as "holo-
type" by Johnson, 1952: 65) MNHN 21212 (l’Isle
de France). Sganzin, 1841, Mém. Soc. Hist. Nat.
Strasbourg 3: 8. Germain, 1911, Bull. Mus. Hist.
Nat. 17: 137. — Haas, 1936, Abh. Senck. Naturf. Ges.
431: 90.
Unio (Lymnium) littoralis (Lamarck). Simpson, 1900,
Proc. U.S. Nat. Mus. 22: 661; 1914, Desc. Cat.
Naiades: 554.
Psilunio littoralis (Lamarck). — Haas, 1940, Zool. Ser.
Field Mus. Nat. Hist. 24: 134.
Caelatura [sic] brevialis (Lamarck). Haas, 1969a,
Superf. Unionacea: 187.
Potomida littoralis (Cuvier). Haas, 1969a, Superf.
Unionacea: 271. — Graf & Cummings, 2007b, J.
Fig. 6. Potomida littoralis (Cuvier). Western Palearctic. A.
MNHN 21212, lectotype of Unio brevialis Lamarck 1819. “l’Isle
de France.” B. MNHN 21213. France.
by listing the locality as “l’Isle de France” that Haas
(1936, 1940, 1969a) consistently treated Unio brevialis
as both a synonym of P. littoralis and a potentially valid
species from Mauritius. Haas, however, also noticed that
Lamarck’s reference to “l’Isle de France” may be to Paris
and the surrounding suburbs rather than an oceanic island.
According to Sganzin (1841: 8), “Lamarck mentionne, je
crois à tort, cette espèce comme se trouvant dans les rivières
de l’Isle-de-France. Les amateurs que j’ai consultés dans
le pays, m’ont assuré qu’elle n’existait pas, et c’est sans
doute par suite de faux renseignements de localités qu’on
lui a donné Maurice pour patrie.” Daget (1998) did not treat
Unio brevialis among the available, Afrotropical/Malagasy
nominal species, and the geographical range of P. littoralis
clearly does not include the Mascarene Islands.
Simpsonella purpurea (Valenciennes)
Figure 7
Anodonta purpurea Valenciennes, 1821. Recueil Observ.
Zool. Anat. Comp. 2: 236, pl. 48 bis, 3a-b. Type speci-
mens unknown. Published locality, “Habitat in insulis
Unio mauritianus Lea, 1859. Proc. Acad. Nat. Sci. Phila.
11: 152; 1860, Jour. Acad. Nat. Sci. Phila. 4: 257,
pl. 40, fig. 138. Holotype (by monotypy) BMNH
1965157 (Mauritius).
Dalliella purpurea (Valenciennes). — Simpson, 1900,
Proc. U.S. Nat. Mus. 22: 833.
Simpsonella purpurea (Valenciennes). — Simpson, 1914,
Desc. Cat. Naiades: 1071. — Haas, 1914, Conch. Cab.
Martini Chemn. 9: 213; 1969a, Superf. Unionacea:
384. — Graf & Cummings, 2007b, J. Moll. Stud. 73:
Material examined.—“Mauritius”: BMNH 1965157
(1 spec.).
Distribution.— Luzon, The Philippines. The reported
type locality of Unio mauritianus Lea, 1859 was errone-
ously listed as “Island of Mauritius.”
Remarks.— Both Simpson (1900, 1914) and Haas
(1914, 1969a) regarded U. mauritianus to be synonymous
with Simpsonella purpurea from the Philippines.
Diplodon fluctiger (Lea)
Figure 8
Unio fluctiger Lea, 1859. Proc. Acad. Nat. Sci. Phila. 11:
152; 1860, Jour. Acad. Nat. Sci. Phila. 4: 250, pl. 39,
fig. 130. Holotype (by monotypy) BMNH 1965169
(locality unknown). — Küster, 1861, Conch. Cab.
Fig. 7. Simpsonella purpurea (Valenciennes). The Philippines.
A. BMNH 1965157, holotype of Unio mauritianus Lea 1859. B.
USNM 5926, type of Unio verecundus Gould 1850.
Fig. 8. Diplodon fluctiger (Lea). South America. A. ANSP 125774.
Labeled as coming from “Mauritius.” B. BMNH 1965169,
holotype of Unio fluctiger. Locality unknown.
Martini Chemn. 9: 237, pl. 80, fig. 1. — Sowerby,
1866, Conch. Icon. 16: pl. 42, sp. 299. Parodiz,
1968, Sterkiana 30: 5.
Nodularia (Nodularia) fluctiger (Lea). — Simpson, 1900,
Proc. U.S. Nat. Mus. 22: 814; 1914, Desc. Cat.
Naiades: 991.
Nodularia (Scabies) fluctigera (Lea). Haas, 1911,
Conch. Cab. Martini Chemn. 9: 107, pl. 10, fig. 8;
1924, Abh. Senck. Naturf. Ges. 38: 191.
Diplodon fluctiger (Lea). — Haas, 1919, Senckenbergiana
1: 190.
Diplodon guaranianus fluctiger (Lea). — Haas, 1930,
Senckenbergiana 12: 187.
Ecuadorea fluctiger (Lea). Modell, 1950, Archiv
Mollusk. 79: 143, pl. 11, fig. 2.
Diplodon (Diplodon) guaranianus fluctiger (Lea). — Haas,
1969a, Superf. Unionacea: 520.
Diplodon fluctiger (Lea). — Simone, 2006, Land Freshw.
Moll. Brazil: 259, fig. 975. — Graf & Cummings,
2007b, J. Moll. Stud. 73: 312.
Material examined.
Unknown locality: BMNH 1965169 (1 spec.).
“Mauritius”: ANSP 125774 (1 spec.).
Distribution. Diplodon fluctiger has been re-
ported from the Yuruari River of Guyana and Venezuela
(Simpson, 1914; Modell, 1950), but the only specimen
of known locality figured by Simone (2006) was ANSP
125774, labeled as from “Mauritius.” Simpson (1900,
1914) and Haas (1911, 1924) regarded Unio fluctiger to
be a Southeast Asian form, although Haas (1919, 1930,
1969a) later regarded it as Neotropical.
Remarks.Unio fluctiger Lea has been a long-
standing source of confusion. It began the 20th century as
a species of Scabies according to Simpson (1900). Haas
(1930, 1969a) later treated it as a subspecies of Diplodon
guaranianus (d’Orbigny 1835), although Parodiz (1968)
disowned it from the Neotropical assemblage. In our opin-
ion, the status of Unio fluctiger has not been settled, but
the record from “Mauritius” is considered to be erroneous
as it is based upon data of poor quality and has not been
substantiated by subsequent collecting.
Any discussion of the freshwater mussels reported
from Madagascar and the Mascarene Islands must be
predicated on the knowledge that the data are extremely
poor. The available information is derived from a small
number of specimen records, and most of them have not
been corroborated by subsequent sampling. Simpson
(1900) and Kobelt (1910) listed no credible species
records from the Mascarenes, and only two species were
listed from Madagascar (Etheria elliptica and Unio
madagascariensis). Except for E. elliptica, most of the
remaining records were subsequently added by Germain
(1911, 1918, 1919, 1921) and through miscellaneous mus-
eum lots of dubious identification. Despite more-recent
sampling on those islands, no additional unionoid mussels
have been recovered on Madagascar or the Mascarenes
(Fischer-Piette and Vukadinovic, 1973; Barré et al.,
1982; Daget, 1998). Most authors have considered those
published records of Germain to be specious. Fischer-
Piette and Vukadinovic (1973: 368) leveled the following
complaint against Germain and his methods:
“Germain ne prenait vraiment aucun soin des
matériaux qu’il avait étudiés, ne leur mettant
bien souvent pas d’étiquettes, ou encore
les mélangeant ainsi que leurs étiquettes
ou les dispersant dans bien des cas, non
seulement n’importe où au Muséum, mais
aussi bien dans son appartement de Paris, sa
villa d’Angers ou le Musée d’Angers. Il en
résulte que beaucoup de ses types passent
maintenant inaperçus, et il se pourrait qu’un
certain nombre soit définitivement perdu.
Le professeur Fischer-Piette tient à faire
connaître clairement cette situation pour ne
pas en être tenu responsable.”
Their statement does little to assuage our concerns about
the quality of the available material.
The records of five species attributed to Mauritius
and Reunion are each the result of single specimens
or only published reports. Four of these are regarded as
representatives of other species, known (or suspected)
from elsewhere: Margaritifera auricularia (+ sinuata),
Potomida littoralis (+ brevialis), Simpsonella purpurea
(+ mauritianus), and Diplodon fluctiger (Simpson,
1914; Haas, 1969a). The fifth, Coelatura cariei, so
resembles Coelatura aegyptiaca from the Nile and West
Africa (Fig. 5) that this record too must be considered
a case of mistaken locality. Thus, it would seem that no
records of the Unionoida from the Mascarene Islands are
viable (Table 1), but this is actually to be expected. The
Mascarenes are oceanic islands, having never been part of
a continental landmass and arising nearly 700 km from the
nearest craton, Madagascar (Abell and Brown, 2005). As
stated above, freshwater mussels are generally regarded as
incapable of breaching long-distance oceanic barriers due
to their parasitic larval stage and dependence upon their
host freshwater fishes for dispersal.
Two of the four reported Malagasy species, Coelatura
madagascariensis and C. malgachensis, are nomina dubia
(Table 1). That leaves only two species to be considered
from Madagascar: Etheria elliptica and Germainaia geayi.
Etheria elliptica is widespread in the Afrotropics,
and therefore its reported occurrence in northwestern
Madagascar might appear insignificant (Fig. 1). It is just
another example of a lineage shared between Africa and
Madagascar (Yoder and Nowak, 2006). However, this
biogeographical pattern is actually quite interesting. The
disjunction of E. elliptica across the Mozambique Channel
could have resulted from two different biogeographical
processes: vicariance or dispersal. Under a vicariance sce-
nario, E. elliptica inhabited Gondwana at least 120 Mya
ago, and when that supercontinent rifted apart (Sanmartín
and Ronquist, 2004), the species persisted on both Africa
and Madagascar, with little (if any) morphological diver-
gence between the isolates. Or, E. elliptica was transplant-
ed from Africa to Madagascar by its host fish (unknown)
or perhaps anthropogenic motives. The evidence currently
available does little to resolve these alternatives, although
it is clear that Etheria is old enough for vicariance.
The global distribution and phylogeny of the
Etheriidae, the family to which Etheria belongs, reflects
the disintegration of Gondwana. Three etheriid genera
Etheria, Acostaea and Pseudomulleria — are each
monotypic and each occurs on a fragment of Gondwana
(Graf and Cummings, 2007b). According to the phylog-
eny of Graf and Cummings (2006b), the relationships
among these genera are as follows: (Etheria, (Acostaea,
Pseudomulleria)). Acostaea and Pseudomulleria are ex-
tremely similar morphologically (Yonge, 1978), and the
major distinction between them is that while Acostaea
is endemic to the Magdalena Basin of Colombia,
Pseudomulleria is known only from southern India (Pain
and Woodward, 1961). Thus, the common ancestor of
the (Acostaea, Pseudomulleria) clade was present on
Gondwana before terrestrial connections between South
America and India were severed. This could have been as
early as 120 Mya when Africa and South America first dis-
sociated from the Madagascar-India block (Sanmartín and
Ronquist, 2004) or as late as 100 or 80 Mya when southern
South America and India-Madagascar may have been con-
nected via Antarctica (Hay et al., 1999; Krause, 2003; Rage,
2003; Evans et al., 2008). It follows from the phylogeny
of the Etheriidae that if the (Acostaea, Pseudomulleria)
lineage was present on Gondwana before South America
and Africa separated from Madagascar and India (as well
as Antarctica, Australia and New Zealand), then so was
Etheria. Thus, the biogeography of the Etheriidae does not
contradict the hypothesis that the disjunction of Etheria
elliptica across the Mozambique Channel is the result of
ancient tectonic action.
However, these biogeographical interpolations pro-
vide no basis to reject the hypothesis that Etheria elliptica
dispersed (or was dispersed) from Africa to Madagascar
at some point (or multiple points) over the last 120 My.
Unfortunately, the fossil record is of little help in this par-
ticular case, as the oldest Etheria fossil globally is only
Miocene in age (Haas, 1969b; Van Damme, 1984). In our
opinion, the absence of older Etheria fossils has less to
do with a possible relatively recent origin for the lineage
and more to do with the limited record of fluvial paleofau-
nas in the Afrotropics (Van Damme, 1984; Kat, 1987; Van
Bocxlaer et al., 2008).
An alternative evolutionary scenario for the Etheriidae
argued by Bogan and Hoeh (2000) and Bogan and Roe
(2008) provides no support for a vicariance hypothesis to
explain the reported disjunction of Etheria populations on
Africa and Madagascar. Employing a dataset composed of
a portion of cytochrome oxidase subunit I mtDNA from
33 freshwater mussel species, including one sequence
each from Etheria, Acostaea, and Pseudomulleria, Bogan
and Hoeh (2000) recovered the Etheriidae as polyphylet-
ic. While Etheria and Acostaea were weakly placed
as a paraphyletic grade at the base of the Neotropical
Mycetopodidae, the position of Pseudomulleria was re-
covered near the base of the Unionidae clade. From this,
a revision of the Etheriidae has been proposed wherein
Etheria elliptica is the solitary representative of that fam-
ily, Acostaea is moved to the Mycetopodidae (along with
Bartlettia, the fourth traditional genus of the Etheriidae)
and Pseudomulleria is classified among the Unionidae
(Bogan and Roe, 2008). Under this scenario, there is no
Gondwanan disjunction among the genera of the Etheriidae
because that family is monotypic — the disjunction across
the Mozambique Channel not withstanding. However, as
we have argued elsewhere (Graf and Cummings, 2006b),
we consider that dataset insufficient to reach such a con-
clusion, and that placement of Pseudomulleria contradicts
a number of otherwise well-supported morphological
synapomorphies supporting the family-level phylogeny of
the Unionoida. These incompatible alternative scenarios
for the evolution of the Etheriidae as well as the shortcom-
ings of the known fossil record leave the problem of the
origins of Malagasy Etheria unresolved.
The state of the available data is even more meager
for Germainaia geayi, but the biogeographical and evo-
lutionary implications for the presence of this species on
Madagascar are even more interesting. This is assuming,
of course, that the three, dead, well-worn specimens (Fig.
3) from an unknown locality in Madagascar actually rep-
resent a distinct Malagasy freshwater mussel species. The
case of G. geayi is distinct from the other freshwater mus-
sels attributed to Madagascar or the Mascarenes by single
specimens or literature records in that the latter could be
regarded as either locality errors for other taxa or unrecog-
nizable. G. geayi has adult types and an adequate descrip-
tion, yet no one has explained away the species.
Germainaia geayi has traditionally been treated as a
member of the family Unionidae. Africa and Madagascar
are not the only Gondwanan fragments inhabited by unio-
nids. India harbors a diverse assemblage of unionid species
(Subba Rao, 1989), and New Guinea also has two species of
the genus Haasodonta, which have historically been classi-
fied as unionid (McMichael and Hiscock, 1958). While we
find it plausible (and beyond the scope of this paper) that a
single lineage of Unionidae may have breeched Wallace’s
Line to invade Australasia from the Sunda Islands, it is
unlikely that any unionid species dispersed across the
substantial oceanic barriers surrounding Madagascar to
colonize the island. Thus, Germainaia geayi (like Etheria
elliptica) presumably represents a vicariant lineage held
over from Madagascar’s tenure as a small, central portion
of the larger Gondwana during the Mesozoic.
The alleged presence of the Unionidae on Madagascar
presents a real challenge to the “Into Africa” hypoth-
esis. That theory argues that the African species of the
Unionidae are the descendants of Eurasian lineages that
spread south following the closure of the Tethys Sea dur-
ing the Miocene (Scotese et al., 1988; Rögl, 1999; Stewart,
2001). As Madagascar has remained isolated from the
northern continents since the break-up of Pangaea during
the Jurassic (Scotese et al., 1988; Sanmartín and Ronquist,
2004), the “Into Africa” hypothesis would predict that
Germainaia geayi arrived on Madagascar by dispersal,
presumably from Africa. Recently, G. geayi has been
treated as a species of the African unionid genus Coelatura
(Daget, 1998; Graf and Cummings, 2007b). Fischer-Piette
and Vukadinovic (1973) went a step further to arrange it
in the subgenus Zairia, otherwise restricted to species like
Coelatura stagnorum (Dautzenberg 1890) of the Lower
Congo in western Central Africa (Fig. 9A) (Graf and
Cummings, 2006a). While the occurrence of a species of
the Unionidae on Madagascar contradicts the “Into Africa”
hypothesis based upon the global biogeography of the fam-
ily, the assumed dispersal abilities of freshwater mussels,
and the currently-available fossil record for these taxa, it
does support the “Out of Africa” hypothesis proposed by
Hoeh et al. (2002) based upon their molecular phyloge-
netic analyses.
We may also be under-emphasizing the role of disper-
sal, as has been common in previous studies of Gondwanan
taxa (Waters and Craw, 2006; Yoder and Nowak, 2006).
Some freshwater mussels, with the aid of their more vagile
host species, may be capable of breeching short oceanic
barriers. Examples include widespread species distributed
across multiple coastal basins on the Eastern Atlantic Slope
of North America (Johnson, 1970; Sepkoski and Rex,
1974) and Anodonta and Margaritifera on the Kuril and
Aleutian islands in the northern Pacific (Starobogatov et
al., 2004). Margaritifera margaritifera is also known from
Iceland, which is quite distant from the European mainland
(Ziuganov et al., 1994). Other explanations besides disper-
sal can be invoked to explain the disjunct distributions of
unionoids on the Atlantic Slope and Pacific archipelagos
such as stream-head piracy or dispersion during low
sea-level periods but M. margaritifera on Iceland was
distributed by its anadromous host salmonids (or by some
other conveyance). Among freshwater mussel species, the
case with Germainaia geayi is distinct in that the process
would have resulted in an island endemic (i.e., disjunction
above the species level). These kinds of dispersal hypoth-
eses are notoriously difficult to falsify.
But what if Germainaia geayi is not actually a member
of the Unionidae? The species was originally assigned to
that family by its description in the genus Unio (Germain,
1911), and subsequent authors have tended to punt with re-
gard to this taxon. The genus Coelatura has been treated as
a catch-all, default genus for Afrotropical unionid species
not assignable to other, more distinctive genera (Mandahl-
Fig. 9. Comparative samples from the Lower Congo and
Australia. A. Coelatura stagnorum (Dautzenberg 1890). ANSP
134032. Boma, Bas-Congo, Congo (DRC). B. Hyridella depressa
(Lamarck 1819). MNHN 4088, type of Unio depressa. Australia.
Barth, 1988; Scholz and Glaubrecht, 2004). Madagascar is
geographically closest to Africa, and Unio geayi Germain
1911 lacks distinctive shell characters, so it was tentatively
placed in Coelatura. It is significant that the arrangement
of this species predated consideration of continental drift
or even the evolutionary implications of supra-specific
classification in malacology. This is a general problem
with the current classification of the Unionoida, and New
Zealand, Australia, and the genus Hyridella, for one exam-
ple, provides an analogous system to Madagascar, Africa,
and Coelatura (Graf and Ó Foighil, 2000; Fenwick and
Marshall, 2006).
An alternative interpretation is that Germainaia
geayi may be a member of the family Hyriidae (Graf and
Cummings, 2007b). The Hyriidae is currently known
from South America and Australasia (McMichael and
Hiscock, 1958; Simone, 2006), as well as the Triassic
of North America (Henderson, 1935; Good, 1998).
Phylogenetically, the Hyriidae is placed in the superfamily
Etherioidea, which has a strictly Gondwanan distribu-
tion, except for a few species of mycetopodids that have
spread north into Mexico from the Neotropics (Graf, 2000;
Graf and Cummings, 2006b). The presence of a hyriid on
Madagascar would be consistent with the prevailing hy-
potheses of freshwater mussel evolution and biogeogra-
phy, and it would remove the need for the “Out of Africa”
or “Into Africa” hypotheses of the origin of the Unionidae
to explain the presence of G. geayi on Madagascar.
Contrary to the paleontological literature, no concho-
logical characteristics have been identified that can defini-
tively diagnose a basal hyriid from a basal unionid (Graf
and Cummings, 2006b). Extant members of certain derived
lineages in each family do indeed have diagnostic shell
characters. For example, Neotropical genera like Diplodon
and Castalia have coarse, radial umbo sculpture. However,
other hyriids have zigzag sculpture or no sculpture at all,
and the same is true for many Old World unionids. It has
previously been observed how similar some of the sculp-
tured unionids of southeastern Asia are to the sculptured
hyriids of South America. For example, Harmandia vs.
Triplodon (= Prisodon), Hyriopsis vs. Prisodon, and
Scabies vs. Diplodon (see the example of Diplodon flucti-
ger above). The family-level placement of all these genera
could readily be settled after examination of diagnostic
characters of the soft-parts (Graf and Cummings, 2006b).
However, no soft-parts are available for Germainaia geayi,
and the unsculptured shells with which we have to work
betray little about the phylogenetic affinities of this fresh-
water mussel.
Based upon the general shell shape, texture of the per-
iostracum and degree of development of the hinge teeth, G.
geayi bears a similarity to Australian hyriid species, like
Hyridella depressa (Lamarck 1819) (Fig. 9B). Other taxa
both plants and animals also reflect this same pat-
tern: Malagasy lineages with closer phylogenetic affinities
to Australasia and southern South America than to either
Africa or India (Sanmartín and Ronquist, 2004). Two spe-
cific examples are rainbow fishes (Melanotaenioidei) and
the recent discovery of Beelzebufo, the giant ceratophryine
anuran, from the upper Cretaceous of Madagascar (Sparks
and Smith, 2004; Evans et al., 2008). The data for the
Unionoida, however, are so meager and of such poor qual-
ity that we can reach no confident conclusion. Thus, we
have classified Germainaia as incertae sedis at the family
Hopefully, our reexamination of the actual and alleged
freshwater mussels of Madagascar and the Mascarene
Islands has clarified the evolutionary and biogeographical
context of those records, even if we have left a number of
important questions unanswered. In our defense, we were
the ones that asked the questions in the first place, and we
consider it an improvement in the quality of knowledge
to make explicit both the knowns and unknowns of any
problem. We feel confident that freshwater mussels do not
occur on the oceanic islands of Reunion and Mauritius,
but the issue of Etheria elliptica and Germainaia geayi
on Madagascar will only be settled by further sampling.
At the most basic level, biotic surveys are necessary to
corroborate these reports of freshwater mussels and de-
termine the distributions of these mollusks on the island.
In the absence of also finding well-dated fossil material,
fresh specimens will also be useful for both (1) compara-
tive anatomical studies and (2) molecular analyses of re-
lationships and estimations of divergence times between
the Malagasy species and their sister groups. While these
interesting questions have been moldering for over a cen-
tury, the threatened nature of Madagascar’s freshwaters
now provides an urgency to finally take up the challenge.
We would like to thank Delphine Brabandt, Jean-
Pierre Rocroi, Virginie Héros and Philippe Bouchet of the
MNHN for their assistance in various capacities, includ-
ing (but not limited to) help navigating the collections and
library in their charge, granting work space during three
separate visits from 2006-2008 and providing digital imag-
es of Unio malgachensis (used in Fig. 4). Anthony Geneva
brought the distribution of Beelzebufo to our attention,
and drafts of this paper were read and improved by Mark
Sabaj Pérez, Jon Gelhaus, Tim Pearce, and an anonymous
reviewer. This research was funded by grants to the authors
from the National Science Foundation (DEB-0316125,
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... The origin of this subfamily is a matter of long-term discussion (Graf & Cummings, 2009;Graf & Cummings, 2011;Graf et al., 2014;Bolotov et al., 2017a). However, a modern biogeographical modelling reveals that it probably arose in East Gondwana in the Jurassic and that its members arrived in Asia using the Indian Plate and Burma Terrane as two 'biotic ferries' (Bolotov et al., 2022). ...
... The Parreysiinae is subdivided into five tribes: Coelaturini Modell, 1942from Africa, and Indochinellini Bolotov, Pfeiffer, Vikhrev & Konopleva, 2018, Lamellidentini Modell, 1942, Leoparreysiini Vikhrev, Bolotov & Kondakov, 2017, and Parreysiini Henderson, 1935 South and Southeast Asia . Whereas the African Coelaturini still needs a thorough modern reappraisal from a taxonomic point of view (Graf & Cummings, 2009;Graf et al., 2014;Ortiz-Sepulveda et al., 2020), the genus-and species-level taxonomy of the Asian Parreysiinae is sufficiently known and is based on modern integrative revisions (Graf, 2013;Bolotov et al., 2017b;Bolotov et al., 2018;Pfeiffer et al., 2018;Bolotov et al., 2020;Bolotov et al., 2022). Recently, several new genera were described from tropical Asia, namely Indochinella Bolotov et al., 2018, Leoparreysia Vikhrev, Bolotov & Aksenova, 2017, Scabiellus Bolotov et al., 2020, and Trapezidens Bolotov, Vikhrev & Konopleva, 2017(Bolotov et al., 2017bBolotov et al., 2018;Bolotov et al., 2020). ...
1. The Western Indochina Subregion (Myanmar) represents a freshwater biodiversity hotspot of worldwide significance and houses a plethora of endemic freshwater species, among which are amphibians, fish, and various aquatic invertebrates. 2. The freshwater mussel (Bivalvia: Unionidae) fauna of western Indochina is characterized by high taxonomic richness, with almost all species and several genera being endemic to the subregion. Furthermore, there are a number of species endemic to a single basin or even to a single tributary of a larger river system (the so-called intra-basin endemic taxa). 3. Here, the discovery of three new, narrowly endemic freshwater mussel species from northern Myanmar is presented: Radiatula kachinensis sp. nov., Trapezidens mogaungensis sp. nov. (upper Ayeyarwady basin), and Lamellidens chindwinensis sp. nov. (upper Chindwin basin). All the new species are upland river specialists, which are under high human pressure as a result of habitat degradation, deforestation, oil palm expansion, river damming, and biological invasions. 4. A nearly complete lack of data on the life cycles and fish hosts should be considered the most striking gap in recent knowledge of tropical Asian freshwater mussels. Here, available data on 27 species belonging to the genera Radiatula, Trapezidens, and Lamellidens are revised. It is shown that certain fish hosts are known for two species only. 5. Further spread of the alien Chinese pond mussels (Sinanodonta woodiana species complex) in Indochina may be considered one of the significant threats to native freshwater mussel populations. Here, it is shown that the temperate invasive lineage of S. woodiana is established in at least three non-native populations in the Ayeyarwady and Salween basins. Moreover, the first arrival of the tropical invasive lineage of S. woodiana to Myanmar is announced, although it has been predicted previously. This lineage was found at two sites on the Shan Plateau (Ayeyarwady basin) close to the Chinese border.
... Examples of such forms are caecilians 55 , frogs 56,57 and freshwater crabs 58 . The origin of the African Coelaturini clade and its sister relationships with Oriental taxa have been under long-term discussions in light of two primary hypotheses: "Into Africa" and "Out of Africa" 32,37,59,60 . With respect to the "Into Africa" hypothesis, the presence of the Unionidae in the Indian subcontinent and Africa can be explained by an invasion of the same Asiatic lineage when these continents contacted Eurasia during the Eocene (India) and Miocene (Africa) 37,59,60 . ...
... The origin of the African Coelaturini clade and its sister relationships with Oriental taxa have been under long-term discussions in light of two primary hypotheses: "Into Africa" and "Out of Africa" 32,37,59,60 . With respect to the "Into Africa" hypothesis, the presence of the Unionidae in the Indian subcontinent and Africa can be explained by an invasion of the same Asiatic lineage when these continents contacted Eurasia during the Eocene (India) and Miocene (Africa) 37,59,60 . By contrast, the "Out of Africa" hypothesis predicts that the Unionidae arose on Gondwana, populating the northern continents from the south 37, 59, 60 . ...
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The concept of long-lived (ancient) lakes has had a great influence on the development of evolutionary biogeography. According to this insight, a number of lakes on Earth have existed for several million years (e.g., Baikal and Tanganyika) and represent unique evolutionary hotspots with multiple intra-basin radiations. In contrast, rivers are usually considered to be variable systems, and the possibility of their long-term existence during geological epochs has never been tested. In this study, we reconstruct the history of freshwater basin interactions across continents based on the multi-locus fossil-calibrated phylogeny of freshwater mussels (Unionidae). These mussels most likely originated in Southeast and East Asia in the Jurassic, with the earliest expansions into North America and Africa (since the mid-Cretaceous) following the colonization of Europe and India (since the Paleocene). We discovered two ancient monophyletic mussel radiations (mean age ~51–55 Ma) within the paleo-Mekong catchment (i.e., the Mekong, Siam, and Malacca Straits paleo-river drainage basins). Our findings reveal that the Mekong may be considered a long-lived river that has existed throughout the entire Cenozoic epoch.
... Mussels of the family Unionidae with 680 described species [1] are important components of freshwater ecosystems. Alarmingly, the International Union for Conservation of Nature and Natural Resources Red List identifies almost 200 species of this family as extinct, endangered, or threatened [2] which makes unionids one of the most endangered groups of invertebrates in the world [3,4]. ...
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Mussels of the family Unionidae are important components of freshwater ecosystems. Alarmingly, the International Union for Conservation of Nature and Natural Resources Red List of Threatened Species identifies almost 200 unionid species as extinct, endangered, or threatened. Their decline is the result of human impact on freshwater habitats, and the decrease of host fish populations. The Thick Shelled River Mussel Unio crassus Philipsson, 1788 is one of the examples that has been reported to show a dramatic decline of populations. Hierarchical organization of riverine systems is supposed to reflect the genetic structure of populations inhabiting them. The main goal of this study was an assessment of the U. crassus genetic diversity in river ecosystems using hierarchical analysis. Different molecular markers, the nuclear ribosomal internal transcribed spacer ITS region, and mitochondrial DNA genes (cox1 and ndh1), were used to examine the distribution of U. crassus among-population genetic variation at multiple spatial scales (within rivers, among rivers within drainages, and between drainages of the Neman and Vistula rivers). We found high genetic structure between both drainages suggesting that in the case of the analyzed U. crassus populations we were dealing with at least two different genetic units. Only about 4% of the mtDNA variation was due to differences among populations within drainages. However, comparison of population differentiation within drainages for mtDNA also showed some genetic structure among populations within the Vistula drainage. Only one haplotype was shared among all Polish populations whereas the remainder were unique for each population despite the hydrological connection. Interestingly, some haplotypes were present in both drainages. In the case of U. crassus populations under study, the Mantel test revealed a relatively strong relationship between genetic and geographical distances. However, in detail, the pattern of genetic diversity seems to be much more complicated. Therefore, we suggest that the observed pattern of U. crassus genetic diversity distribution is shaped by both historical and current factors i.e. different routes of post glacial colonization and history of drainage systems, historical gene flow, and more recent habitat fragmentation due to anthropogenic factors.
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This paper discusses the life and works of Richard Irwin Johnson (1925-2020), who made significant contributions to our knowledge of the Unionidae (Mollusca: Bivalvia) through his numerous publications and his curation of the sizable collections of freshwater bivalves at the Museum of Comparative Zoology, Harvard University. Johnson also published extensively on the history of malacology, including biographical accounts and museum histories. His 135 publications on mollusks spanned 74 years (from 1941 at age 16 to 2015 at age 90), nearly setting a record for malacology, and his membership in the American Malacological Union / Society for 79 years (1941 to 2020) outlasted any other current or former member. Johnson amassed one of the largest ever private libraries of books and journals on mollusks, and contributed significantly to the growth of the MCZ Malacology Library.
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The tribes Contradentini and Rectidentini (Unionidae) comprise a diverse clade of freshwater mussels endemic to South-east Asia. Our understanding of the diversity and phylogeny of this radiation has improved dramatically in recent years, but this systematic transformation has not yet benefited from comprehensive museum sampling or phylogenomic methods. A synthetic taxonomic revision of the Contradentini+Rectidentini that leverages these useful and accessible methods is needed. We set out to (1) generate a phylogenomic reconstruction of the supraspecific relationships of the Contradentini+Rectidentini using anchored hybrid enrichment, (2) revise the taxonomy and geographic boundaries of the generic and species-level diversity of the radiation, and (3) identify patterns of freshwater mussel diversity and distribution in this clade and discuss the processes that may have precipitated them. Our phylogenomic reconstruction using over 1600 loci, with a total alignment length of over a half a million nucleotides, recovers a well supported phylogeny of the clade that resolves four independent multispecies radiations endemic to the Mekong drainage. We examined, digitised, and imaged 1837 records from 15 natural history museums that provided the necessary data to document the morphological variation and geographic distributions of the focal taxa. We also analysed 860 COI sequences, 519 of which were generated in this study, to better understand the species boundaries and geographic distributions of the recovered clades. We recognise 54 valid species in the tribes Contradentini and Rectidentini, including 9 described herein as new to science. Out of this revision emerged several interesting biogeographic patterns that appear to have resulted from recent stream capture, historical confluence, and intradrainage barriers to dispersal. We hypothesise that these phenomena shaped the diversity and distribution of the Contradentini+Rectidentini, contributing to the formation of several characteristic freshwater mussel provinces in South-east Asia.
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The objective of this review is to update our previously published checklist of Recent freshwater mussel species and genera (Graf & Cummings, 2007, J. Molluscan Stud.: 291–314) to reflect the new data and research findings that have accumulated over the last decade. The MUSSEL Project Database was developed to synthesize the available taxonomic nomenclature, species ranges and published taxonomic hypotheses on genus–species combinations and synonymy. We have found 4,988 available species-group level nominal species representing 958 valid species in 192 genera worldwide, an increase of 118 species since 2007. The current patterns of species richness are discussed with regard to both taxonomy and geography, as is the general flux in the number of species recognized over time. A checklist is provided herein, with a bibliography to key faunistic and taxonomic references. The full dataset is maintained and updated on the MUSSEL Project Web Site (
The Indotropical freshwater mussel assemblage has more genera of uncertain subfamily-level position (i.e. genera incertae sedis) than all other regional faunas. Of the 16 genera incertae sedis in the Indotropics, only two, Harmandia and Unionetta, are distributed in the mainland southeast Asia subregion. Resolving the enigmatic systematic position of Harmandia and Unionetta would finally establish a complete subfamily-level classification for the freshwater mussel genera of southeast Asia and facilitate more comprehensive evaluation of regional freshwater mussel diversity and distribution. Molecular phylogenetic reconstructions using the nuclear–encoded large ribosomal subunit rRNA (28S) and the mitochondrial protein-coding cytochrome c oxidase subunit I (COI) recovered Harmandia and Unionetta in the Indo-Afrotropical subfamily Parreysiinae, and more specifically as members of the tribe Indochinellini (formerly Oxynaiini). Harmandia is shown to be polyphyletic with its former species belonging to three distantly related clades of the Unionoida (i.e. Parreysiinae, Rectidentinae and Hyriidae). Unionetta was likewise not recovered as monophyletic, despite the strong morphological similarities and close geographic proximity of the sequenced individuals. Based on a synthesis of molecular, morphological and biogeographic data, the taxonomy and geographic distributions of Harmandia and Unionetta are revised. These results are discussed in the context of the dispersal of the Parreyssiinae into Southeast Asia and the species-level diversity of the Indochinellini in the Mekong River.
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The International Union for Conservation of Nature (IUCN) is the premier global biodiversity conservation organization. Its Red List is a rigorous vehicle for assessing the conservation status of plant and animal species. However, although all animal and bird species recognized by IUCN have been evaluated , only a tiny fraction of invertebrates have been evaluated. As a measure of the numbers of extinct species (since around the year 1500) the Red List is probably quite accurate for birds and mammals, but severely underestimates the numbers for invertebrates. Nonetheless, molluscs stand out as the major group most severely impacted by extinction, with 297 of the 744 animal species listed as extinct in the third issue of the 2016 Red List. Here we review efforts to obtain a more realistic , albeit less rigorous, assessment of the numbers of extinct mollusk species. Our approach has been based on biblio-graphic research and consultation with experts, rather than following the highly detailed but restrictive IUCN Categories and Criteria. In 2009, this led to an assessment that 533 mol-lusk species were extinct, far more than the number on the Red List. In the present study we revisited this approach and here list 638 species as extinct, 380 as possibly extinct, and 14 as extinct in the wild, a total of 1,032 species in these combined categories, and more than twice as many as listed by IUCN in these categories. However, this approach only considers species for which information is available; it is therefore biased. In a study published in 2015 we developed an alternative approach, based on a random global sample of land snails, and estimated that 3,000–5,100 mollusk species have gone extinct. We review the main reasons for these extinctions: habitat destruction, impacts of introduced species, exploitation and collecting, and, potentially, climate change, and discuss relevant case studies.