An Updated Classification of the Recent Crustacea

that the trichodactylids may represent an independent
lineage from any of the other freshwater crab
families and that they are descended from portunoid
stock is supported by a number of independent
studies using morphological data (e.g., Rodriguez,
1982; Magalhães and Türkay, 1996a–c;
Sternberg, 1997; Sternberg et al., 1999; and Sternberg
and Cumberlidge, in press). Possible corroboration
from preliminary molecular evidence (18S,
16S, and 12S rDNA), which is admittedly based on
only a handful of freshwater and marine crab species,
neither strongly supports nor falsifies this relationship
(Abele et al., 1999; Spears et al., 2000).
Based on the totality of the evidence available to
us, we have transferred the freshwater crab family
Trichodactylidae to the marine superfamily Portunoidea.
Superfamily Bythograeoidea
Since the discovery of crabs at hydrothermal vents
and the erection of a new superfamily and family
(Bythograeidae) to accommodate them (Williams,
1980), there has been much discussion concerning
the origins and affinities of these crabs (e.g., see
Guinot, 1988, 1990; Hessler and Martin, 1989).
Williams (1980) noted morphological similarities
between bythograeids and portunoids, xanthoids,
and potamoids. Guinot (1988) argued for a recent
derivation of the hydrothermal crab fauna. Bythograeids
are morphologically similar to certain xanthoids,
and there are some spermatozoal similarities
as well (Tudge et al., 1998). It may be that, at some
point, the bythograeids should be transferred to the
Xanthoidea. For now, we have left them in their
own superfamily.
Superfamily Xanthoidea
The former xanthids are now treated as a superfamily
containing 11 families, a recognition of the
group’s diversity that many workers feel is long
overdue. The former family Xanthidae contained a
wide variety of disparate forms and was the largest
single family of the Decapoda, with an estimated
130 genera and over 1,000 species (Rice, 1980;
Martin, 1988). Manning and Holthuis (1981) list
no fewer than 32 family and subfamily names that
have been proposed for various assemblages within
the family. Our elevation of the former subfamilies
follows mostly the recommendations of Guinot
(1977, 1978). A similar subdivision was provided
by Serène (1984), although his treatment was restricted
to those taxa found in the Red Sea, and so
some xanthoid groups (such as the Panopeidae)
were not considered by him. Serène (1984) recognized
a Xanthoidea containing only five families
(Xanthidae, Trapeziidae, Pilumnidae, Carpiliidae,
and Menippidae), most with a fairly large number
of subfamilies, some of which we are now treating
as families. There is recent molecular evidence suggesting
that at least some of these former subfamilies
are indeed distinct and warrant separate family
status (e.g., see Schubart et al., 2000b, for the Panopeidae).
Coelho and Coelho Filhol (1993) suggested
splitting the former Xanthidae into four
families (Carpiliidae, Xanthidae [containing the
subfamilies Menippinae, Platyxanthinae, Xanthinae,
and Eucratopsinae], Eriphiidae, and Pilumnidae
[with subfamilies Trapeziinae and Pilumninae]).
One of the problems in elevating the various
xanthid groups is that currently there are no published
lists of which genera should be included in
which family. The field worker who previously
could place any xanthoid crab in the Xanthidae is
now faced with the rather challenging task of wading
through a large amount of primary literature to
locate the appropriate family; a further problem is
that the primary literature often does not contain
all of this information either. Like so many other
groups of crustaceans, the ‘‘xanthoid’’ crabs are in
need of revision, both taxonomic and phylogenetic
(see also Coelho and Coelho Filhol, 1993).
Peter Ng (pers. comm.) feels that the name Eriphiidae
MacLeay, 1838, is a senior synonym and
should be used instead of Menippidae Ortmann,
1893, for this family, and indeed some workers
(e.g., Ng, 1998) have employed the name Eriphiidae.
Serène (1984) and other workers have occasionally
treated the Eriphiinae as a subfamily of the
Menippidae. The family Oziidae Dana, 1852, is apparently
a senior synonym of Menippidae as well,
as pointed out by Holthuis (1993b), and probably
should be used in place of Menippidae if Ozius and
Menippe are both considered members of this
group. However, we continue to use Menippidae in
this case because the current (fourth) edition of the
ICZN allows continued recognition of a name that
is enjoying ‘‘prevailing use,’’ and in our estimation,
replacing Menippidae with Oziidae or Eriphiidae
would cause more confusion than maintaining use
of Menippidae. Hendrickx (1998) elevated the former
goneplacid subfamily Pseudorhombilinae to
family status to accommodate six goneplacid-like
genera; hence, our inclusion of the family Pseudorhombilidae
Alcock, 1900, among the xanthoids.
The Eumedonidae, a family of crabs symbiotic
on echinoderms, has at times been recognized as a
distinct family (Lim and Ng, 1988; Števčić et al.,
1988; and P. Ng, pers. comm.; see Chia and Ng,
2000), and it is often placed within the Xanthoidea,
although exactly where it belongs in relation to other
crab families is still somewhat uncertain. Most
workers are in agreement that early attempts to
place it among the parthenopoids were misguided
(e.g., see Van Dover et al., 1986; Števčić et al.,
1988; Ng and Clark, 1999, 2000) and that it is
probably a xanthoid (Števčić et al., 1988). Daniele
Guinot (pers. comm.), who earlier listed the family
in its own superfamily, the Eumedonoidea Miers
(see Guinot, 1985), now also suggests that it might
belong in the Xanthoidea, possibly close to the Pilumnidae,
a view shared by Van Dover et al. (1986)
based on larval evidence. Most recently, Ng and
Clark (1999, 2000) have arrived at the conclusion
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