20
mm used for SEM), and 5 Q Q 21.2 (20.0- 22.0)
mm; HMPS VII/a-2770 Fort Collins, Colorado, USA
20" 0"19.6,21.8 mm, 2 Q Q 20.9,21.8 mm; USNM
91857 Alton, St. Tammany Parish, Louisiana, USA
50" 0"18.8 (18.3-19.4) mm, 5 Q Q 17.4 (17.2-17.9)
mm.
Diagnosis. Male. Peduncle of distal outgrowth of intermediate type; rotation of hand not more than 40°; inner
side of proximal part of peduncle without protuberances, peduncle with pulvinus; spur acuminate; inner
lamella medioventrall y produced forming a cavity; distal part of thumb inerm, geniculate, apex acuminate;
finger bigeniculate two teeth on inner dorsal side of
proximal part; proximal tooth semi-triangular, distal
one digitiform; apex of finger inerm and acuminate;
frontal appendage simple and usually bilobed at tip;
genitalia with a pair of lateral linguiform outgrowths;
scleroid cercopods, fused with telson and spinose distally; anus ventrally subterminal.
Female. Ovaries uniramous; cysts sphaerical, ornamented by ribs forming polygonal areas.
Differential diagnosis. The distinction between S.
sealii and the two American species of the same group,
S. similis and S. woottoni, is based upon the number
and shape of the teeth of the finger, the linguiform
genital outgrowths, and the cercopods. S. sealii has
two teeth, and a pair of linguiform outgrowths (Fig.
2 C, D), while S. similis has three teeth, two on the
inner dorsal side, and a small one on the dorsal side,
and no linguiform outgrowths (Fig. 3 C, D). S. woottoni presents the linguiform outgrowths (Fig. 4 D) and
two teeth on the finger. However, while in S. sealii
the proximal tooth is semi-triangular (Saunders, 1981,
Figs 24,25; Eng et al., 1990, Fig. 5 a), and the distal
one digitiform (Fig. 2 C), in S. woottoni the proximal
tooth is spatulate and the distal one semi-rectangular
(Fig. 4 C). S. sealii, like S. similis, has spinose cercopods, while S. woottoni has setose ones. The main
differences of the African species of the sealii group
with respect to S. sealii are: S. bourquinii Hamer &
Appleton, 1993, presents a long, ridge-like distal tooth
and setose cercopods; S. distinctus Thiele, 1907, and S.
spinosus Daday, 1908, similarly to S. bourquinii bear a
ridge-like distal tooth, and the three species have genitalia without linguiform outgrowths (Maeda-Martinez
etat., 199).
Distribution. S. sealii is currently recognized as the
most widely distributed anostracan in the New World
(Moore, 1966; Eng et aI., 1990). It has been recorded
from Canada in Alberta, and Saskatchewan, from the
United States in Alabama, Arizona, California, Colorado, Florida, Georgia, Illinois, Kansas, Kentucky,
Louisiana, Maryland, Minnesota, Missouri, Montana,
North Carolina, North Dakota, New Jersey, New York,
Nebraska, Oklahoma, Oregon, South Carolina, Texas,
Virginia, Washington, and from Mexico in Veracruz
(Dexter, 1959; Belk, 1975) and Chiapas (Belk et ai.,
1990).
Remarks. Because of its extensive geographical range,
Moore (1966) stressed the need for a morphological
study of populations from different regions. However, no differences between populations from Virginia
and Mississipi were found by Creaser (1930), nor from
Louisiana, Mississipi, Florida Oklahoma and Kansas
by Moore (1966). We found, only in males, differences in a pair of conical protuberances, dorsolaterally
located on the posterior border of genital and abdominal segments. Yet, this character is variable within
populations and deserves further study. Eight males
from Leon, Florida (DB 1092), present only one pair
of these protuberances on abdominal segment 1; five
males from Alton, Louisiana (USNI 91857) also bear a
pair on abdominal segment 1, but two of them present
another pair on genital segment 2, and one male from
Blanco, Texas (DB 263), bears a pair of protuberances
on genital segments 1 & 2, and on abdominal segment 1. Because of the diversity of habitats where S.
sealii has been collected, and the differences in hatching temperature and egg size between melt pool and
rain pool populations, Belk et al. (1990) and Eng et
al. (1990) suggested that this species is either physiologically labile, composed by physiological races, or
constitutes a complex of sibling species.
Streptocephalus similis Baird, 1852
(Fig. 3 A-E)
Streptocephalus similis Baird, 1852; Packard,
1883; Daday, 1910; Creaser, 1930; Mackin, 1942;
Moore, 1958, 1966; Dexter, 1959; Brtek, 1974; Belk,
1975; Spicer, 1985; Pennak, 1989; Maeda-MartInez,
1991.
Type material. Deposited at the British Museum.
Type locality. Santo Domingo, Hispaniola Island.
Material examined. DB 965 Kenedy, Texas, USA 4 0"
0"17.8 (17.4-18.5)mm, 2 Q Q 17.5,18.5 mm; HMPS
mm used for SEM), and 5 Q Q 21.2 (20.0- 22.0)
mm; HMPS VII/a-2770 Fort Collins, Colorado, USA
20" 0"19.6,21.8 mm, 2 Q Q 20.9,21.8 mm; USNM
91857 Alton, St. Tammany Parish, Louisiana, USA
50" 0"18.8 (18.3-19.4) mm, 5 Q Q 17.4 (17.2-17.9)
mm.
Diagnosis. Male. Peduncle of distal outgrowth of intermediate type; rotation of hand not more than 40°; inner
side of proximal part of peduncle without protuberances, peduncle with pulvinus; spur acuminate; inner
lamella medioventrall y produced forming a cavity; distal part of thumb inerm, geniculate, apex acuminate;
finger bigeniculate two teeth on inner dorsal side of
proximal part; proximal tooth semi-triangular, distal
one digitiform; apex of finger inerm and acuminate;
frontal appendage simple and usually bilobed at tip;
genitalia with a pair of lateral linguiform outgrowths;
scleroid cercopods, fused with telson and spinose distally; anus ventrally subterminal.
Female. Ovaries uniramous; cysts sphaerical, ornamented by ribs forming polygonal areas.
Differential diagnosis. The distinction between S.
sealii and the two American species of the same group,
S. similis and S. woottoni, is based upon the number
and shape of the teeth of the finger, the linguiform
genital outgrowths, and the cercopods. S. sealii has
two teeth, and a pair of linguiform outgrowths (Fig.
2 C, D), while S. similis has three teeth, two on the
inner dorsal side, and a small one on the dorsal side,
and no linguiform outgrowths (Fig. 3 C, D). S. woottoni presents the linguiform outgrowths (Fig. 4 D) and
two teeth on the finger. However, while in S. sealii
the proximal tooth is semi-triangular (Saunders, 1981,
Figs 24,25; Eng et al., 1990, Fig. 5 a), and the distal
one digitiform (Fig. 2 C), in S. woottoni the proximal
tooth is spatulate and the distal one semi-rectangular
(Fig. 4 C). S. sealii, like S. similis, has spinose cercopods, while S. woottoni has setose ones. The main
differences of the African species of the sealii group
with respect to S. sealii are: S. bourquinii Hamer &
Appleton, 1993, presents a long, ridge-like distal tooth
and setose cercopods; S. distinctus Thiele, 1907, and S.
spinosus Daday, 1908, similarly to S. bourquinii bear a
ridge-like distal tooth, and the three species have genitalia without linguiform outgrowths (Maeda-Martinez
etat., 199).
Distribution. S. sealii is currently recognized as the
most widely distributed anostracan in the New World
(Moore, 1966; Eng et aI., 1990). It has been recorded
from Canada in Alberta, and Saskatchewan, from the
United States in Alabama, Arizona, California, Colorado, Florida, Georgia, Illinois, Kansas, Kentucky,
Louisiana, Maryland, Minnesota, Missouri, Montana,
North Carolina, North Dakota, New Jersey, New York,
Nebraska, Oklahoma, Oregon, South Carolina, Texas,
Virginia, Washington, and from Mexico in Veracruz
(Dexter, 1959; Belk, 1975) and Chiapas (Belk et ai.,
1990).
Remarks. Because of its extensive geographical range,
Moore (1966) stressed the need for a morphological
study of populations from different regions. However, no differences between populations from Virginia
and Mississipi were found by Creaser (1930), nor from
Louisiana, Mississipi, Florida Oklahoma and Kansas
by Moore (1966). We found, only in males, differences in a pair of conical protuberances, dorsolaterally
located on the posterior border of genital and abdominal segments. Yet, this character is variable within
populations and deserves further study. Eight males
from Leon, Florida (DB 1092), present only one pair
of these protuberances on abdominal segment 1; five
males from Alton, Louisiana (USNI 91857) also bear a
pair on abdominal segment 1, but two of them present
another pair on genital segment 2, and one male from
Blanco, Texas (DB 263), bears a pair of protuberances
on genital segments 1 & 2, and on abdominal segment 1. Because of the diversity of habitats where S.
sealii has been collected, and the differences in hatching temperature and egg size between melt pool and
rain pool populations, Belk et al. (1990) and Eng et
al. (1990) suggested that this species is either physiologically labile, composed by physiological races, or
constitutes a complex of sibling species.
Streptocephalus similis Baird, 1852
(Fig. 3 A-E)
Streptocephalus similis Baird, 1852; Packard,
1883; Daday, 1910; Creaser, 1930; Mackin, 1942;
Moore, 1958, 1966; Dexter, 1959; Brtek, 1974; Belk,
1975; Spicer, 1985; Pennak, 1989; Maeda-MartInez,
1991.
Type material. Deposited at the British Museum.
Type locality. Santo Domingo, Hispaniola Island.
Material examined. DB 965 Kenedy, Texas, USA 4 0"
0"17.8 (17.4-18.5)mm, 2 Q Q 17.5,18.5 mm; HMPS