Hydrobiologia 298: 241-243, 1995.
D. Belk, H. J. Dumont & G. Maier (eds j, Studies on Large Branchiopod Biology and Aquaculture II.
© 1995 Kluwer Academic Publishers.
241
Uncovering the Laurasian roots of Eubranchipus
Denton Belk
Biology Department, Our Lady of the Lake University of San Antonio, San Antonio, TX 78207-4666, USA
Key words: anostracan genera, generic characters
Abstract
The species of the anostracan genus Eubranchipus Verrill, 1870 can be recognized as belonging to the same taxon
and unambiguously distinguished from all other taxa in the family Chirocephalidae Daday, 1910 by the common
morphology of their eversible penes. These reproductive structures are short, fat, and cylindrical with a single long,
thin spine on the lateral margin at the tip of each penis. This ends the erroneous perception of Eubranchipus as a
New World genus and recognizes it as an old taxon with members distributed across the modern continents that
once comprised Laurasia.
Introduction
Linder (1941) built a strong foundation under the taxonomy of higher categories in the Anostraca by focusing on the importance of genital morphology. Applying
this approach, he united a number of natural groupings
which Daday (1910) had separated as a result of his
reliance on antennal morphology to the neglect of genital characters. The work Linder started is, however,
not yet complete. For many species and several genera
we still have major gaps in our knowledge of genital
morphology.
In one case I think needs correcting, Brtek (1962)
favored antennal characters over genital morphology when he elevated Simon's (1886) subgenera
Drepanosurus and Siphonophanes to generic ranking.
The full exposition of his reasoning is presented in
Brtek (1966) where he grouped all of the species in the
family Chirocephalidae having short, fat, cylindrical
penes with a single long thin spine on the lateral margin at the tip of each penis (Fig. 1) into the subfamily
Eubranchipodinae Daday, 1910. In doing this, he overlooked what I consider the significant fact that all of the
other genera he recognized in his important monograph
on Chirocephalidae have uniform eversible penis morphology. There is one caveat to this last statement; the
eversible penis morphology of the monotypic genus
Phallocryptus Biraben, 1951 remains unknown.
Defining anostracan genera
In deciding how genera should be delineated within
the Anostraca, I think we are well served by carefully
considering Alain Dubois' treatise on the meaning of
the genus in zoology (Dubois, 1988). Dubois points
out that while most zoologists would agree 'a genus
groups together species closer to each other than to
species of other genera'; the problem comes in defining what is meant by 'close'. He thus concludes, ' ... the
whole "genus problem" boils down to deciding which
information must be carried by the generic name.' To
improve the information content of the genus category
in anostracan taxonomy, I think we need to pay attention to how the structures we use in diagnosing genera
function in anostracan biology. While doing this, we
need to keep in mind another of Dubois' points, 'The
genus, contrary to the species, is a collective unit, and
the first function of the generic name is to express
similarity, not difference.'
In male anostracans, structures of the antennae,
nonretractile penes, and probably the first three legs in
Dendrocephalus and the spines found on various parts
of the abdomen of species in several genera, function
in mate recognition. I review the experimental evidence supporting this in Belk (1991). I suggested in the
1991 paper that for females other than Artemia some
stimulus provided by the eversible penis during copulation may function to trigger the movement of ripe
D. Belk, H. J. Dumont & G. Maier (eds j, Studies on Large Branchiopod Biology and Aquaculture II.
© 1995 Kluwer Academic Publishers.
241
Uncovering the Laurasian roots of Eubranchipus
Denton Belk
Biology Department, Our Lady of the Lake University of San Antonio, San Antonio, TX 78207-4666, USA
Key words: anostracan genera, generic characters
Abstract
The species of the anostracan genus Eubranchipus Verrill, 1870 can be recognized as belonging to the same taxon
and unambiguously distinguished from all other taxa in the family Chirocephalidae Daday, 1910 by the common
morphology of their eversible penes. These reproductive structures are short, fat, and cylindrical with a single long,
thin spine on the lateral margin at the tip of each penis. This ends the erroneous perception of Eubranchipus as a
New World genus and recognizes it as an old taxon with members distributed across the modern continents that
once comprised Laurasia.
Introduction
Linder (1941) built a strong foundation under the taxonomy of higher categories in the Anostraca by focusing on the importance of genital morphology. Applying
this approach, he united a number of natural groupings
which Daday (1910) had separated as a result of his
reliance on antennal morphology to the neglect of genital characters. The work Linder started is, however,
not yet complete. For many species and several genera
we still have major gaps in our knowledge of genital
morphology.
In one case I think needs correcting, Brtek (1962)
favored antennal characters over genital morphology when he elevated Simon's (1886) subgenera
Drepanosurus and Siphonophanes to generic ranking.
The full exposition of his reasoning is presented in
Brtek (1966) where he grouped all of the species in the
family Chirocephalidae having short, fat, cylindrical
penes with a single long thin spine on the lateral margin at the tip of each penis (Fig. 1) into the subfamily
Eubranchipodinae Daday, 1910. In doing this, he overlooked what I consider the significant fact that all of the
other genera he recognized in his important monograph
on Chirocephalidae have uniform eversible penis morphology. There is one caveat to this last statement; the
eversible penis morphology of the monotypic genus
Phallocryptus Biraben, 1951 remains unknown.
Defining anostracan genera
In deciding how genera should be delineated within
the Anostraca, I think we are well served by carefully
considering Alain Dubois' treatise on the meaning of
the genus in zoology (Dubois, 1988). Dubois points
out that while most zoologists would agree 'a genus
groups together species closer to each other than to
species of other genera'; the problem comes in defining what is meant by 'close'. He thus concludes, ' ... the
whole "genus problem" boils down to deciding which
information must be carried by the generic name.' To
improve the information content of the genus category
in anostracan taxonomy, I think we need to pay attention to how the structures we use in diagnosing genera
function in anostracan biology. While doing this, we
need to keep in mind another of Dubois' points, 'The
genus, contrary to the species, is a collective unit, and
the first function of the generic name is to express
similarity, not difference.'
In male anostracans, structures of the antennae,
nonretractile penes, and probably the first three legs in
Dendrocephalus and the spines found on various parts
of the abdomen of species in several genera, function
in mate recognition. I review the experimental evidence supporting this in Belk (1991). I suggested in the
1991 paper that for females other than Artemia some
stimulus provided by the eversible penis during copulation may function to trigger the movement of ripe