The Pachynidae fam. nov. (Crustacea: Amphipoda: Lysianassoidea) 3246
Author
Lowry, J. K.
Author
Stoddart, H. E.
text
Zootaxa
2012
2012-03-23
3246
1
1
69
https://biotaxa.org/Zootaxa/article/view/zootaxa.3246.1.1
journal article
10.11646/zootaxa.3246.1.1
11755334
5249007
Ultimachelium nichollsi
(
Lowry, 1984
)
(
Figs 44
,
45
)
Pachychelium antarcticum
. ―
Nicholls, 1938: 14
, fig. 3. ―
Bellan-Santini, 1972: 215
, pl. 28. ―
Lowry & Bullock, 1976: 101
(in part). ―
Lowry, 1982: 320
.
Pachychelium nichollsi
Lowry, 1984: 103
. ―
Barnard & Karaman, 1991: 510
. ―
De Broyer & Jazdzewski, 1993: 72
.
Ultimachelium nichollsi
. ―
De Broyer
et al
., 2007: 158
.
Material examined.
One
?female,
12 mm
,
USNM 1156710
, off
South Georgia
,
Southern Ocean
,
54°51'S
35°03'W
,
168–173 m
, trawl,
10 December 1986
,
Professor Siedlecki
,
USARP
cruise 601, stn 74. –1?male, 10.0 mm,
USNM 1157037
, unknown locality, stn AH 4-30. –1?male,
11.5 mm
,
USNM 1157039
, unknown locality, stn AH 4-40
.
Diagnostic description.
Head
lateral cephalic lobe large, narrowly rounded; ventral margin subsigmoidal.
Antenna 1
peduncular article 1 without posterodistal spine; accessory flagellum 2-articulate, article 1 long; flagellum with strong callynophore in specimens of unknown sex.
Mandible
lacinia mobilis absent; lamina dentata absent; accessory setal row absent; molar absent; palp attached distally; palp article 2 broad, as long as article 3; article 3 tapered distally.
Maxilla 1
outer plate with 6 setal-teeth in 3/3 arrangement, setal-teeth smooth; palp absent.
Maxilliped
inner plate absent; outer plate medium size; palp 4-articulate, article 4 large.
Gnathopod 1
subchelate;
ischium smaller than propodus
;
merus with anterior margin
; carpus extremely compressed; propodus length about 1.9 × breadth, posterior margin extremely reduced, with produced corner, corner of palm without robust seta; dactylus reaching to corner of palm.
Gnathopod 2
palm minute, obtuse.
Pereonite 4
without dorsal spines.
Pereonite 5
without dorsal spines.
Pereopod 5
merus without posteroproximal shoulder.
Pereopod 6
basis with posteroventral lobe weakly produced; merus longer than broad, without posteroproximal shoulder.
Pereopod 7
basis subrectangular, posterodistal corner subquadrate
, posterior margin weakly dentate;
merus, length of anterior margin 2.6 × proximal breadth
.
Epimeron 3
posterior margin without projections, posteroventral corner subacute.
Uropod 3
biramous, inner ramus just reaching base of article 2 or extending beyond article 1 of outer ramus.
Telson
slightly shorter than broad, entire.
Remarks.
Ultimachelium barnardi
and
U. nichollsi
both have six setal-teeth on the outer plate of maxilla
1 in
a 3/3 arrangement. They differ in the shape of mandibular palp article 3 (subparallel sides in
U. barnardi
, tapering distally in
U. nichollsi
); and gnathopod 1 ischium (swollen posteroproximally in
U. nichollsi
, not swollen in
U. barnardi
).
Distribution.
South Georgia
, Southern Ocean and Adelie Coast,
Antarctica
;
46–732 m
depth.