6.11 Philomedes cubitum Kornicker, 1975
Philomedes cubitum Kornicker, 1975: pp. 289293, figs. 132, 178, 179.
Carapace length -
females: 1.39-1.40 mm (Kornicker, 1975)
males: 1.59 mm
Female. Carapace mediumsized, subovate;
height about 2/3 the length; rostrum curved and
overhanging, with a flattened tip; incisure narrow and deep; no trace of a cauda; dorsal margin
more or less evenly rounded but steeply truncate
in the rear; ventral margin evenly rounded from
the broadly subacuminate posterior to the incisure. Infold broad; rostral infold carrying about
21 bristles; anterior infold finely striate with
ah out 9 short bristles; postero-ventral and posterior infold bearing about 25 bristles; selvage
forming a right-angled elbow on the posteroventral infold of both valves ( species character).
Al sensory bristle without long filaments. A2 endopod 2-jointed. 7th limb with 3 dorsal and 2
ventral distal bell bristles, plus a total of 17 proximal bell bristles. Furca lamellar, with 5 stout followed by 5 weaker claws. Lateral eyes minute,
each with 2 ommatidia; medial eye large. Upper
lip hirsute, bearing a single elongate process.
Rod-shaped organ long and slender, 2-jointed,
with a rounded tip (Kornicker 1975).
Male. Carapace similar to that of the female except that the incisure is more open. Al sensory
with long filaments, 'c' and 'f' bristles extremely
long. A2 endopod 3-jointed. Maxilla reduced
compared with that of the female.
Remarks
Kornicker (1975) described only the female and
an N -1 male of this species, because there were
no mature males in the RV Hero cruise 69-5 type
material, nor did the species occur in any other
collections which he examined. Our only specimen, recognized by the elbow-like bend in the
posterior selvage as belonging to P. cubitum, was
a mature male close to the size limit set by Kornicker (1975) for the species. This unique specimen has been donated to the United States Museum of Natural History: Smithsonian Institution, Washington, D.C., USA (USNM Catalogue
No. 194145). Unfortunately, because of the thin
shell, attempts to carry out SEM photography of
the specimen were unsuccessful (Kornicker,
pers. comm.). It is ofinterest to add that the Antarctic and Subantarctic are areas of greatest diversity for the genus Philomedes (Kornicker
1975, figs. 132, 135).
Distribution
The material described by Kornicker (1975) was
collected by RV Hero at two stations in the Straits
of Magellan (53°32'5, 72°29'W, and 53°41'
40"S, 72°45"W) and from depths of 21.328.0 m. Our mature male was collected at St. 21
(52° 52 'S, 70° 30'W). Since there are no other records, the species appears tobe confined to shallow depths in the Straits and the Magellanic subregion of the sub-Antarctic, as defined by Kornicker (1975).
Philomedes cubitum Kornicker, 1975: pp. 289293, figs. 132, 178, 179.
Carapace length -
females: 1.39-1.40 mm (Kornicker, 1975)
males: 1.59 mm
Female. Carapace mediumsized, subovate;
height about 2/3 the length; rostrum curved and
overhanging, with a flattened tip; incisure narrow and deep; no trace of a cauda; dorsal margin
more or less evenly rounded but steeply truncate
in the rear; ventral margin evenly rounded from
the broadly subacuminate posterior to the incisure. Infold broad; rostral infold carrying about
21 bristles; anterior infold finely striate with
ah out 9 short bristles; postero-ventral and posterior infold bearing about 25 bristles; selvage
forming a right-angled elbow on the posteroventral infold of both valves ( species character).
Al sensory bristle without long filaments. A2 endopod 2-jointed. 7th limb with 3 dorsal and 2
ventral distal bell bristles, plus a total of 17 proximal bell bristles. Furca lamellar, with 5 stout followed by 5 weaker claws. Lateral eyes minute,
each with 2 ommatidia; medial eye large. Upper
lip hirsute, bearing a single elongate process.
Rod-shaped organ long and slender, 2-jointed,
with a rounded tip (Kornicker 1975).
Male. Carapace similar to that of the female except that the incisure is more open. Al sensory
with long filaments, 'c' and 'f' bristles extremely
long. A2 endopod 3-jointed. Maxilla reduced
compared with that of the female.
Remarks
Kornicker (1975) described only the female and
an N -1 male of this species, because there were
no mature males in the RV Hero cruise 69-5 type
material, nor did the species occur in any other
collections which he examined. Our only specimen, recognized by the elbow-like bend in the
posterior selvage as belonging to P. cubitum, was
a mature male close to the size limit set by Kornicker (1975) for the species. This unique specimen has been donated to the United States Museum of Natural History: Smithsonian Institution, Washington, D.C., USA (USNM Catalogue
No. 194145). Unfortunately, because of the thin
shell, attempts to carry out SEM photography of
the specimen were unsuccessful (Kornicker,
pers. comm.). It is ofinterest to add that the Antarctic and Subantarctic are areas of greatest diversity for the genus Philomedes (Kornicker
1975, figs. 132, 135).
Distribution
The material described by Kornicker (1975) was
collected by RV Hero at two stations in the Straits
of Magellan (53°32'5, 72°29'W, and 53°41'
40"S, 72°45"W) and from depths of 21.328.0 m. Our mature male was collected at St. 21
(52° 52 'S, 70° 30'W). Since there are no other records, the species appears tobe confined to shallow depths in the Straits and the Magellanic subregion of the sub-Antarctic, as defined by Kornicker (1975).