16
South and East Asia, and from the latter area, a rather
recent dispersal to North America.
During a comparative study of the North American
species with those from Africa, Europe, and India, we
found that the morphology of the peduncle of the distal
antennal outgrowth and the binamous ovaries developed in seven North American species can be useful
for understanding the probable phylogeny of the New
World species. The results of our phylogenetic analysis support the thesis proposed by Belk (1984), and
solve the incongruent species relationships of Spicer
(1985). Thus, the objectives of the present study are
(1) to update the diagnosis of the New World species,
(2) to describe three new species, (3) to elaborate a key
to the species, and (4) to discuss the phylogeny ofthe
group.
Material and methods
The material examined came from collections deposited at several institutions and from one private collection, viz Museo de Zoologia, Escuela Nacional
de Estudios Profesionales, Iztacala, UNAM, Mexico (ENEP), Hornonitrianske Muzeum Prievidza, Slovakia (HMPS), Natural History Museum of Los Angeles County, California, USA (LACM), Laboratory of
Animal Ecology, University of Ghent, Belgium (UG),
Escuela Superior de Biologia, Universidad Juarez del
Estado de Durango, Mexico (UJED), National Museum of Natural History, Smithsonian Institution, USA
(USNM), and Dr D. Belk's collection (DB). Holotypes,
allotypes, and paratypes of the new species are deposited at the Smithsonian Institution. Paratypes are also
deposited at the Universidad de Durango, University
of Ghent and in D. Belk's collection. We follow the
classification of the Streptocephalus species and the
method to measure and to name the parts and regions
of the body proposed by Maeda-Martinez et al. (1995;
this volume). The references for synonymy are limited
to the original one of each name, and include only those
references of comprehensive studies on the distribution
and diagnosis of the species, and identification keys.
The descriptions of cyst morphology are according to
Mura (1992). In the taxonomic account, measures of
the total length are given. In most samples with three
or more specimens, the average and range are given.
The measurements were carried out with an eye-piece
micrometer on a stereo microscope Wild M3. Total
length was measured to the nearest 0.18 mm, ventral side up. For scanning electron micrographs, fixed
specimens were critical-point dried, coated with gold
(9 nm, Balzers Union SCD 040) and analyzed under a
JEOL JSM 840 (SEM) at 10 kYo
The phylogeny of the group is discussed on the
basis of (1) the systematic approach presented by
Maeda-Martinez et at. (1995; this volume) and (2) a
cladistic study. Two cladistic analyses were carried out
with the aid of the HennigI86 computer program. In the
first one, the 13 New World species with 21 characters
were included. In the second one, besides the former
species, seven African forms (S. dendyiBarnard, 1929,
S. rothschildi Daday, 1908, S. zeltneri Daday, 1910, S.
distinctus Thiele, 1907, S. ovamboensis Barnard, 1924,
S. rubricaudatus (Klunzinger, 1867) and S. torvicornis (Waga, 1842)) with 25 characters were analyzed.
The character state polarities were established upon
the ontogeny (Kitching, 1992; Nelson, 1978; Spicer,
1985) of S. dichotomus, S. proboscideus (Frauenfeld,
1873) and S. torvicornis, all of them cultured in the
Laboratory of Animal Ecology, University of Ghent,
Belgium (Maeda-Martinez et at., 1995), and on the
postembryonic development of S. torvicornis and S.
sealii as described by Claus (1886) and Baqai (1963).
Only the character polarity of the ovaries was defined
by in-group commonality. As spicer (1985) indicated,
the use of an outgroup for comparison is not possible,
because most of the characters used are from the distal antennal outgrowth, and no other anostracan group
exhibits such a complex process. The morphological
characters and their states used for obtaining cladograms are as follows (a = apomorphic, p = plesiomorphic): l.-Peduncle of distal antennal outgrowth; short
or intermediate (p), long (a). For coding the character
into discrete states, we used the "gap coding" method
(Archie, 1985). Fifty nine samples containing 3 or up to
12 specimens, were classed according to their peduncle type (Maeda-Martinez et al., 1995). Thus, three
groups were formed, i.e. group 1, with 98 specimens
within species with short peduncles; group 2, with 67
specimens within 6 species with intermediate ones;
and group 3, with 28 specimens within 15 species with
long peduncles. Of each sample the average values of
the ratio pd/sl (peduncle/standard length) were calculated. The mean of the averages of the samples of each
group, and the pooled within-group standard deviation
were calculated. Given that the averages of groups 1
and 2 were separated by a gap smaller than one pooled
within-group standard deviation (i.e. the selected critical gap size), both groups were determined a being
in the plesiomorphic state (Fig. 14). In contrast, group
3 was defined to be in apomorphic state, because the
South and East Asia, and from the latter area, a rather
recent dispersal to North America.
During a comparative study of the North American
species with those from Africa, Europe, and India, we
found that the morphology of the peduncle of the distal
antennal outgrowth and the binamous ovaries developed in seven North American species can be useful
for understanding the probable phylogeny of the New
World species. The results of our phylogenetic analysis support the thesis proposed by Belk (1984), and
solve the incongruent species relationships of Spicer
(1985). Thus, the objectives of the present study are
(1) to update the diagnosis of the New World species,
(2) to describe three new species, (3) to elaborate a key
to the species, and (4) to discuss the phylogeny ofthe
group.
Material and methods
The material examined came from collections deposited at several institutions and from one private collection, viz Museo de Zoologia, Escuela Nacional
de Estudios Profesionales, Iztacala, UNAM, Mexico (ENEP), Hornonitrianske Muzeum Prievidza, Slovakia (HMPS), Natural History Museum of Los Angeles County, California, USA (LACM), Laboratory of
Animal Ecology, University of Ghent, Belgium (UG),
Escuela Superior de Biologia, Universidad Juarez del
Estado de Durango, Mexico (UJED), National Museum of Natural History, Smithsonian Institution, USA
(USNM), and Dr D. Belk's collection (DB). Holotypes,
allotypes, and paratypes of the new species are deposited at the Smithsonian Institution. Paratypes are also
deposited at the Universidad de Durango, University
of Ghent and in D. Belk's collection. We follow the
classification of the Streptocephalus species and the
method to measure and to name the parts and regions
of the body proposed by Maeda-Martinez et al. (1995;
this volume). The references for synonymy are limited
to the original one of each name, and include only those
references of comprehensive studies on the distribution
and diagnosis of the species, and identification keys.
The descriptions of cyst morphology are according to
Mura (1992). In the taxonomic account, measures of
the total length are given. In most samples with three
or more specimens, the average and range are given.
The measurements were carried out with an eye-piece
micrometer on a stereo microscope Wild M3. Total
length was measured to the nearest 0.18 mm, ventral side up. For scanning electron micrographs, fixed
specimens were critical-point dried, coated with gold
(9 nm, Balzers Union SCD 040) and analyzed under a
JEOL JSM 840 (SEM) at 10 kYo
The phylogeny of the group is discussed on the
basis of (1) the systematic approach presented by
Maeda-Martinez et at. (1995; this volume) and (2) a
cladistic study. Two cladistic analyses were carried out
with the aid of the HennigI86 computer program. In the
first one, the 13 New World species with 21 characters
were included. In the second one, besides the former
species, seven African forms (S. dendyiBarnard, 1929,
S. rothschildi Daday, 1908, S. zeltneri Daday, 1910, S.
distinctus Thiele, 1907, S. ovamboensis Barnard, 1924,
S. rubricaudatus (Klunzinger, 1867) and S. torvicornis (Waga, 1842)) with 25 characters were analyzed.
The character state polarities were established upon
the ontogeny (Kitching, 1992; Nelson, 1978; Spicer,
1985) of S. dichotomus, S. proboscideus (Frauenfeld,
1873) and S. torvicornis, all of them cultured in the
Laboratory of Animal Ecology, University of Ghent,
Belgium (Maeda-Martinez et at., 1995), and on the
postembryonic development of S. torvicornis and S.
sealii as described by Claus (1886) and Baqai (1963).
Only the character polarity of the ovaries was defined
by in-group commonality. As spicer (1985) indicated,
the use of an outgroup for comparison is not possible,
because most of the characters used are from the distal antennal outgrowth, and no other anostracan group
exhibits such a complex process. The morphological
characters and their states used for obtaining cladograms are as follows (a = apomorphic, p = plesiomorphic): l.-Peduncle of distal antennal outgrowth; short
or intermediate (p), long (a). For coding the character
into discrete states, we used the "gap coding" method
(Archie, 1985). Fifty nine samples containing 3 or up to
12 specimens, were classed according to their peduncle type (Maeda-Martinez et al., 1995). Thus, three
groups were formed, i.e. group 1, with 98 specimens
within species with short peduncles; group 2, with 67
specimens within 6 species with intermediate ones;
and group 3, with 28 specimens within 15 species with
long peduncles. Of each sample the average values of
the ratio pd/sl (peduncle/standard length) were calculated. The mean of the averages of the samples of each
group, and the pooled within-group standard deviation
were calculated. Given that the averages of groups 1
and 2 were separated by a gap smaller than one pooled
within-group standard deviation (i.e. the selected critical gap size), both groups were determined a being
in the plesiomorphic state (Fig. 14). In contrast, group
3 was defined to be in apomorphic state, because the