An Updated Classification of the Recent Crustacea

Cunningham (1999) data, which suggest placement
in the galatheoid clade), Galatheoidea, Paguroidea,
and Hippoidea (spermatozoal characters of which
are described by Tudge et al., 1999). The paguroids
(which in our scheme include the former coenobitoids)
and hippoids should be considered sister taxa
and together are the sister taxon to the Galatheoidea,
according to Morrison and Cunningham
(1999) and C. Morrison (pers. comm.).
INFRAORDER BRACHYURA
Subsequent to the Bowman and Abele (1982) classification,
there has been relatively widespread use
of a scheme first suggested by Guinot (1977, 1978,
1979; see also Saint Laurent, 1979; Guinot and
Bouchard, 1998) that recognizes three morphological
‘‘grades’’ of brachyuran crabs (which she called
the Podotremata, Heterotremata, and Thoracotremata)
based mostly on the coxal vs. sternal location
of the male and female genital apertures. Although
Abele (1991) and Spears et al. (1992) found no molecular
support for these divisions, some spermatological
data seemed to support them (e.g., see Jamieson,
1994; Jamieson et al., 1994a, b, 1995). The
latter two groups (Heterotremata and Thoracotremata)
were treated jointly as the Eubrachyura by
Saint Laurent (1980a, b), and various authors (e.g.,
Schram, 1986) have followed this arrangement as
well. At the same time, there is also growing evidence
from molecular sequence data (e.g., Spears et
al., 1992; Abele and Spears, 1997; Spears and
Abele, 1999; Spears, pers. comm.) and from mitochondrial
gene rearrangement data (Morrison and
Cunningham, 1999; Morrison, pers. comm.) that
the true crabs (Brachyura) can be divided into two
major clades, one containing the dromiacean families
and the other containing all ‘‘higher’’ crabs,
and including the raninids. The two ideas are not
totally incompatible, but at the same time, they
cannot be completely reconciled. The main areas of
disagreement concern the limits of the ‘‘true’’ crabs,
the placement of several families traditionally
thought of as being ‘‘primitive’’ (dromiids and raninids
in particular), and the recognition of various
assemblages (tribes, sections, etc.) within the major
divisions. Evidence brought to bear on these issues
has come from many fields, such as larval morphology
(e.g., Rice, 1980, 1983, 1988; Martin,
1988, 1991), sperm morphology (e.g., Jamieson,
1991a, b, 1994), adult morphology (e.g., Števčić,
1995, 1998; McLay, 1991, 1999; Guinot and Bouchard,
1998), and molecular sequence data (e.g.,
Spears et al., 1992).
Guinot (1977, 1978) originally defined the section
Podotremata as containing the dromioids,
homoloids, raninoids, and tymoloids. The Podotremata
was suggested to be monophyletic on the basis
of sperm ultrastructure (Jamieson, 1994) and yet
paraphyletic on the basis of rRNA sequences
(Spears and Abele, 1988; Spears et al., 1992). To
quote Guinot and Bouchard (1998), ‘‘Monophyly
versus paraphyly of the Podotremata and their possible
placement as the sister group of the heterotreme-thoracotreme
assemblage remain open questions.’’
Within the Podotremata, Guinot (1977,
1978) recognized a subsection Dromiacea to contain
two superfamilies, Dromioidea and Homolodromioidea,
and a subsection Archaeobrachyura to
contain the superfamilies Raninoidea, Homoloidea,
and Tymoloidea. The molecular data (e.g., Spears
et al., 1992; Spears and Abele, 1999; Morrison and
Cunningham, 1999; Spears, pers. comm.) do not
support this arrangement. Although one group of
crabs, corresponding to the Dromiacea of Guinot
and earlier workers, does appear separate from other
‘‘higher’’ crabs, nearly all evidence to date points
to the fact that the raninids are not members of this
dromioid clade (in contrast with the conclusions of
Števčić, 1973, 1995, 1998), and thus the Podotremata
cannot be recognized as originally envisioned.
Instead, the raninids appear to be basal members
of the second ‘‘higher crab’’ clade.
Thus, we have decided to abandon the concept
of the Podotremata. The Brachyura is herein depicted
as being composed of two major clades. The
groups formerly treated as ‘‘podotremes’’ are split,
with dromiaceans in one major clade and all other
crabs in the other major clade. We are referring to
the first clade as the section Dromiacea, a name
that has much historical usage and that is well
known among brachyuran researchers. This clade
(section Dromiacea) is the sister group to all of the
higher crab families. In our treatment, it contains
the superfamily Homolodromioidea and its sole
family Homolodromiidae, the superfamily Dromioidea
containing the families Dromiidae and Dynomenidae,
and the superfamily Homoloidea containing
the Homolidae, Latreilliidae, and Poupiniidae
(the latter established by Guinot, 1991).
The second major clade (all other crab families
and superfamilies) is then treated collectively as the
section Eubrachyura, a name coined by Saint Laurent
(1980a, b) for this assemblage (but now including
the raninoids, which were excluded by
Saint Laurent). We note, however, that Števčić
(1973, 1995, 1998) would retain raninids with
dromiids, and Jamieson et al. (1994b) argue, based
on sperm morphology, against any raninid/higher
crab sister group relationship. Inclusion of the raninoids
among the Eubrachyura also might be questioned
on the basis of the fact that they lack the
‘‘sella turcica’’ of the endophragmal system (see Secretan,
1998). Within this enormous clade Eubrachyura,
we are recognizing three subsections.
First, we are treating the raninids and their allies
(the former tymolids, now treated as the Cyclodorippoidea;
see below) as the subsection Raninoida.
We could have used for this group the name Archaeobrachyura,
a name that has been used previously
for the assemblage that contained raninoids,
homoloids, and tymoloids (Saint Laurent 1980a, b)
while they were still considered members of the
‘‘podotreme’’ lineage. However, use of the name Ar-
Contributions in Science, Number 39 Rationale 49