An Updated Classification of the Recent Crustacea

parasites of early fish-like vertebrates as represented
by the conodonts, many of which were present in
the Cambrian.
The classification we follow for the pentastomids
is from Riley (1986; see also Riley et al., 1978).
This classification has been questioned recently by
Almeida and Christoffersen (1999), who do not
consider pentastomes to be crustaceans. Almeida
and Christoffersen suggest, based on a cladistic
analysis of available genera, the recognition of the
Raillietiellida as a new order to contain their new
family Raillietiellidae (for the genus Raillietiella),
the recognition of the Reighardiida as a new order
to contain the family Reighardiidae, and the dissolution
of the family Sambonidae. Additionally,
the Porocephalida was partitioned by them into
two superfamilies. We have not followed the Almeida
and Christoffersen (1999:702) classification
here.
Authority for the taxon name Pentastomida was
somewhat difficult to decipher. Riley (pers. comm.)
informs us that the name ‘‘Pentastomum’’ was first
employed by Rudolphi (1819) to refer to a single
species, and several workers (e.g., Almeida and
Christoffersen, 1999) credit the taxon name Pentastomida
to Rudolphi. We have been unable to locate
a work by Rudolphi in 1819 and suspect that
Rudolphi, 1809, was the intended reference, as Rudolphi
described the genus Pentastoma and used
the group name Pentastomata in this 1809 work
(L. Holthuis, pers. comm.). Diesing (1836) first
used it (as Pentastoma) for the entire group, although
the rank was not given. Elevation to phylum
status was not suggested until 1969 (Self,
1969), although his evidence and reasoning were
flawed (Riley, pers. comm.). Prior to that, there
were various spellings and ranks assigned (e.g., by
Heymons, 1935; Fain, 1961; and others; see Riley,
1986). Thus, because Diesing was the first to use
the name Pentastoma for the entire assemblage, we
have attributed the authorship of the Pentastomida
to him.
Riley (1986) also was of the opinion that pentastomids
were allied with arthropods and probably
with crustaceans, noting that ‘‘the available evidence
overwhelmingly indicates that pentastomids
are euarthropods and, more specifically, that their
affinities are closer to crustaceans than uniramians.’’
More recently, however, he has indicated that
the return to the status of separate phylum is probably
warranted (pers. comm., 1998). Riley’s (1986)
classification (his table 1), which we have followed,
recognized nine families in two orders. Two suborders
of the Porocephalida are mentioned in Riley’s
text, but he chose not to recognize them in his
table, and we have followed his lead.
The inclusion of pentastomids among the Crustacea
takes the known morphological diversity and
lifestyle extremes of the Crustacea—already far
greater than for any other taxon on earth—to new
heights. How many other predominantly marine invertebrate
taxa can claim to have representatives
living in the respiratory passages of crocodilians,
reindeer, and lions?
SUBCLASS MYSTACOCARIDA, ORDER
MYSTACOCARIDIDA
To our knowledge, there have been no suggested
changes in the classification of, or in our understanding
of the phylogeny of, the mystacocarids
since Bowman and Abele (1982). The subclass continues
to be represented by a single extant order
(Mystacocaridida) and family (Derocheilocarididae).
In their review of crustacean relationships
based on 18S rDNA, Spears and Abele (1997) noted,
within the maxillopodan groups, that ‘‘the long
branch leading to the first lineage, the Mystacocarida,
indicates extensive divergence relative to other
crustaceans.’’ Schram et al. (1997) suggest a mystacocarid
copepod lineage; a relationship with
copepods has also been suggested by Boxshall and
Huys (1989) and Walossek and Muller (1998). The
group was most recently reviewed by Boxshall and
Defaye (1996) and Olesen (2001).
SUBCLASS COPEPODA
What could have been a truly daunting task for us
has been made considerably easier by the relatively
recent publication of Copepod Evolution by Huys
and Boxshall (1991), by Damkaer’s (1996) list of
families of copepods (along with their type genus),
and by three recent treatments of copepods by Razouls
(1996, free-living copepods), Raibaut (1996,
parasitic copepods), and Razouls and Raibaut
(1996, phylogeny and classification). Our acceptance
of the Huys and Boxshall classification resulted
in 26 families that have been added, while
18 families recognized by Bowman and Abele have
been replaced, resulting in a net gain of 8 families.
Additional families have been described or recognized
since then (listed below). Huys and Boxshall
(1991) proposed some rather sweeping changes in
some of the higher taxonomic levels as well. Indeed,
most of the suborders and superfamilies appearing
in the Bowman and Abele (1982) list have been
suppressed. This tack was taken also by Damkaer
(1996), although he does not cite Huys and Boxshall.
Where the two classifications differ, we tended
to follow Huys and Boxshall (1991), and readers
are referred to that tome for arguments underlying
these changes. However, we must also point out
that not everyone has accepted the changes suggested
by Huys and Boxshall (1991) (see especially
the critique by Ho, 1994a). Indeed, Huys continues
to use the superfamily concept in some instances
(see Huys and Lee, 1999, for the Laophontoidea)
even though it was not used in Huys and Boxshall
(1991). W. Vervoort (pers. comm.) reminds us that
‘‘a subdivision of a subclass the size as that of the
Copepoda will always remain a matter of personal
choice,’’ and indeed some of the changes advocated
by Huys and Boxshall have been corrected by these
same authors in subsequent personal communica-
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