An Updated Classification of the Recent Crustacea

animal phyla.’’ For the Crustacea, these characters
have been invoked mostly for resolving relationships
within the Eumalacostraca. This work is being
championed primarily by B. G. Jamieson and
C. Tudge and their colleagues. Some of the many
recent papers advocating sperm ultrastructural
characters in phylogeny are Guinot et al. (1994,
primitive crabs; 1997, freshwater crabs; 1998,
dromiacean crabs), Richer de Forges et al. (1997,
crabs), Jamieson (1989a, b, crabs; 1989c, stomatopods;
1990, primitive crabs; 1991a, overview of
crustacean sperm ultrastructure and phylogeny;
1991b, 1993, 1994, crabs), Jamieson et al. (1993a–
c, crabs; 1994a, b, 1995, 1996, 1997, crabs), Jamieson
and Tudge (1990, crabs), Jamieson, Tudge,
and Scheltinga (1993, primitive crabs), Jespersen
(1979, leptostracans), Grygier (1981, 1982, maxillopodans),
Storch and Jamieson (1992, pentastomids),
Tudge (1991, 1992, 1995, 1997a, b, 1999a,
b, anomuran decapods), Tudge et al. (1998a, lithodid
crabs; 1998b, hydrothermal vent crabs), and
Tudge et al. (2000, mud-shrimp families; 1999, hippoid
crabs). Many of these papers and their contributions
are discussed in the sections dealing with
the taxa in question.
Some of the revelations from the study of sperm
ultrastructure are not terribly surprising and in fact
support previous long-standing hypotheses of crustacean
relationships (e.g., peracarid unity; Jamieson,
1991a). Other results are more controversial
and include the alliance of the Remipedia with the
Maxillopoda on the basis of the shared ‘‘flagellate
condition’’ of their spermatozoon (Jamieson,
1991a) and placing the genus Lomis outside of, and
thalassinids within, the Anomura (Tudge, 1997a, b)
(in contrast with what Morrison and Cunningham,
1999, presented based on mitochondrial gene rearrangement
data). [As an aside, the congruence between
the phylogenetic diagrams of Jamieson
(1991a:111), based on sperm ultrastructure, and
Schram (1986), based on cladistic analysis of morphological
characters, is perhaps not so remarkable
as Schram and Hof (1998) suggest. Schram and
Hof (1998) refer to Jamieson’s figure and ask the
reader to ‘‘note the general correspondence with the
major classes as arranged in Fig. 6.1.A.’’ However,
Jamieson’s figure was in turn based on Schram
(1986) with a diagram of the spermatozoal ultrastructure
simply added to Schram’s tree; it is not an
independently derived phylogeny.] Continued use
of sperm ultrastructure in crustacean taxonomy
and systematics will almost certainly contribute significantly
to our understanding of crustacean phylogeny.
LARVAL MORPHOLOGY AND
CLASSIFICATION OF THE CRUSTACEA
The study of crustacean systematics and phylogeny
has involved larval characters from the very earliest
times. For many groups of crustaceans, a study of
systematic relationships is a study of the larvae, as
these are often the only characters, or the best characters,
that we have. For example, it could be argued
that, until recently, the history of studies in
barnacle phylogeny has been essentially a history
of comparisons of barnacle larvae, and to some extent
this is true for many groups. For some taxa, in
particular the Facetotecta, the larvae are all that we
know; the adult has yet to be recognized or described.
The reverse is also true: there are still some
important groups of crustaceans (the class Remipedia,
for example) for which the larval forms have
never been identified. Many of the classic treatments
of crustacean larvae were published prior to
the Bowman and Abele (1982) classification and
were thus available for consideration by those authors.
The summary of crustacean larval diversity
published by Williamson in that same series of volumes
(Williamson, 1982) remains a good entry
point for the literature on crustacean larvae and
relationships based on larval characters.
In the years following the Bowman and Abele
(1982) classification, there have been additional
and significant treatments of crustacean larval characters
and phylogeny. Indeed, nearly every modern
publication that describes a larval stage includes at
least some comments on the applicability of the
findings to relationships within the group. The
study of larval crabs, in particular, has been a rich
source of new characters for postulating higher level
relationships among the Brachyura (e.g., see
Rice, 1980, 1981, 1983, 1988; Martin, 1984,
1988; Martin et al., 1985; Felder et al., 1985, as a
few selected examples from a huge body of literature
on crab relationships based on larvae and postlarvae).
Williamson (1988a, b) has proposed rather
drastic changes in our understanding of various
pleocyemate groups (particularly the position of the
dromiid crabs relative to anomurans and true
crabs, the placement of the mysidaceans within the
Eucarida, and the separation of palinurid lobsters
from other eucarids based on their bizarre larvae).
Grygier (1987a–c) and others have used larval
characters to explore maxillopod phylogeny; within
the Maxillopoda, the work of Dahms (e.g., Dahms,
1990) could be mentioned for advancing our understanding
of copepod naupliar characters in phylogeny.
Discoveries of fossilized larvae, in particular
papers on the ‘‘Orsten’’ fauna, have added new
characters and new insights into the evolution of
early crustaceans and ‘‘stem-line’’ crustaceans (e.g.,
see Müller and Walossek, 1985a, 1986b; Walossek,
1993, 1995; Walossek and Müller, 1990, 1997).
Walossek and Müller (1997) recognize the Entomostraca,
and exclude from the Crustacea the Pentastomida,
in part based on larval evidence.
We have tried to mention studies based on larval
characters (where they have a bearing on classification
at the family level or higher) under each
crustacean taxon. A recent review of larval diversity
(Harvey et al., in press) provides additional material
geared primarily for the beginning student of
carcinology.
Contributions in Science, Number 39 General Introduction 9