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6.12 Paradoxostoma sp. aff. hypselum
Mtiller, 1908
Paradoxostoma hypselum Miiller, 1908: pp. 118119, with 3 textfigs- Benson, 1964: p. 12, figs. 4,
5, pl. 1 fig. 2 - Neale, 1967: p. 9, pl. 1 figs g, kMcKenzie, 1972a: p. 161- Kornicker, 1975: p. 235
- Hartmann, 1986: p. 172- Hartmann, 1987: p.
131- Hartmann, 1989: p. 250, figs. 61,62- Hartmann, 1990: p. 210.
Carapace length -
females: 0.70-0.73 mm (Miiller, 1908)
males: 0.70-0.73 mm (Miiller, 1908)
Female. Carapace small-medium (for a podocopid), shape subrhomboid; height:length ratia
0.55-0.60, greatest height posteromedial; dorsal
margin strongly arched; ventral margin curved
upwards posteriorly to make a weak ca uda above
the midline with the postero-dorsal edge, but
slightly inflexed anteromedially; anterior more
narrowly rounded, trending antero-ventrally;
surface smooth; colour brownish-yellowish. Inner lamella broad, line of concrescence submarginal, vestibule large, extending from front to
rear; marginal pare canals few and short; normal
canals scattered, simple; central adductors in a
subvertical row of 4, set medially; hinge adont.
Alllimbs elongate and slender. Al 6-segmented;
A2 5-segmented (including protopod), flagellum
reaching beyond the terminal claws, with a large
spinneret gland proximally; mandible coxale
styliform, palp reduced, 2-segmented; oral cone
with a suctorial apparatus (generic character);
maxillule epipod with 14 strahlen, plus 2 downwards-pointing setae, palp missing, 3lobes slender; Pl pediform, protopod armed with a powerful dorsodistal unguiform spine (generic characOrder Podocopida
Planktonic/Benthic Podocopida
Family Paradoxostomatidae
ter); P2 and P3 also pediform but carrying bristles only on the protopods; posterior of the body
lobate, with a spinulose tip; eye large, located anterodorsally.
Male. Similar in many respects to the female, except that the posterior of the body is not as produced. Hemipenis with a large subovate posterior capsule, anterior process broadly triangular,
wedge-shaped.
Remarks
This species was identified in many samples, including some in which planktonic ostracods predominated; e.g. we found 64 specimens at St. 22
(52°40'5, 69°55'W). In a comment on symbiosis
among Ostracoda, McKenzie (1972a) noted that
he had identified as Paradoxostoma cf. hypselum
a specimen forwarded by Kornicker which had
been removed from inside the shell of the myodocopid Philomedes assimilis and near, " ... the
area of muscle of the protopodite of the second
antenna ... " (L.S. Kornicker, pers. comm. 16 December 1971). McKenzie (1972a) recorded further that this individual when dissected had
what appeared to be a piece of tissue attached
near its suctorial apparatus, with its styliform
mandibles both oriented correctly for suctorial
feeding, i.e. aligned near the mouth. This suggests that some paradoxostomatids may parasitize epibenthic myodocopids. In the Magellan
Straits samples collected by the Italian Antarctic
Expedition, however, none of the few philomedids proved to have P. hypselum within their
shells, so McKenzie's interesting earlier interpretation could not be tested further. Our abundant
material of this taxon is referred only tentatively
to P. hypselum because, although the shell shape
6.12 Paradoxostoma sp. aff. hypselum
Mtiller, 1908
Paradoxostoma hypselum Miiller, 1908: pp. 118119, with 3 textfigs- Benson, 1964: p. 12, figs. 4,
5, pl. 1 fig. 2 - Neale, 1967: p. 9, pl. 1 figs g, kMcKenzie, 1972a: p. 161- Kornicker, 1975: p. 235
- Hartmann, 1986: p. 172- Hartmann, 1987: p.
131- Hartmann, 1989: p. 250, figs. 61,62- Hartmann, 1990: p. 210.
Carapace length -
females: 0.70-0.73 mm (Miiller, 1908)
males: 0.70-0.73 mm (Miiller, 1908)
Female. Carapace small-medium (for a podocopid), shape subrhomboid; height:length ratia
0.55-0.60, greatest height posteromedial; dorsal
margin strongly arched; ventral margin curved
upwards posteriorly to make a weak ca uda above
the midline with the postero-dorsal edge, but
slightly inflexed anteromedially; anterior more
narrowly rounded, trending antero-ventrally;
surface smooth; colour brownish-yellowish. Inner lamella broad, line of concrescence submarginal, vestibule large, extending from front to
rear; marginal pare canals few and short; normal
canals scattered, simple; central adductors in a
subvertical row of 4, set medially; hinge adont.
Alllimbs elongate and slender. Al 6-segmented;
A2 5-segmented (including protopod), flagellum
reaching beyond the terminal claws, with a large
spinneret gland proximally; mandible coxale
styliform, palp reduced, 2-segmented; oral cone
with a suctorial apparatus (generic character);
maxillule epipod with 14 strahlen, plus 2 downwards-pointing setae, palp missing, 3lobes slender; Pl pediform, protopod armed with a powerful dorsodistal unguiform spine (generic characOrder Podocopida
Planktonic/Benthic Podocopida
Family Paradoxostomatidae
ter); P2 and P3 also pediform but carrying bristles only on the protopods; posterior of the body
lobate, with a spinulose tip; eye large, located anterodorsally.
Male. Similar in many respects to the female, except that the posterior of the body is not as produced. Hemipenis with a large subovate posterior capsule, anterior process broadly triangular,
wedge-shaped.
Remarks
This species was identified in many samples, including some in which planktonic ostracods predominated; e.g. we found 64 specimens at St. 22
(52°40'5, 69°55'W). In a comment on symbiosis
among Ostracoda, McKenzie (1972a) noted that
he had identified as Paradoxostoma cf. hypselum
a specimen forwarded by Kornicker which had
been removed from inside the shell of the myodocopid Philomedes assimilis and near, " ... the
area of muscle of the protopodite of the second
antenna ... " (L.S. Kornicker, pers. comm. 16 December 1971). McKenzie (1972a) recorded further that this individual when dissected had
what appeared to be a piece of tissue attached
near its suctorial apparatus, with its styliform
mandibles both oriented correctly for suctorial
feeding, i.e. aligned near the mouth. This suggests that some paradoxostomatids may parasitize epibenthic myodocopids. In the Magellan
Straits samples collected by the Italian Antarctic
Expedition, however, none of the few philomedids proved to have P. hypselum within their
shells, so McKenzie's interesting earlier interpretation could not be tested further. Our abundant
material of this taxon is referred only tentatively
to P. hypselum because, although the shell shape