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
Pachychelium
Stephensen, 1925
Pachychelium
Stephensen, 1925: 121
. ―
Schellenberg, 1926: 296
. ―Schellenberg, 1931: 18. ―K.H.
Barnard, 1932: 75
. ―J.L.
Barnard, 1969a: 354
. ―
Lowry, 1984: 99
. ―
Barnard & Karaman, 1991: 509
.
Type
species
.
Pachychelium davidis
Stephensen, 1925
, by monotypy.
Diagnostic description.
Body shape slender.
Head lateral cephalic lobe large, narrowly rounded
. Antenna 1 peduncular article 1 without posterodistal spine; accessory flagellum article 1 long; [callynophore not known for female]. Mandible with accessory setal row absent; left lamina dentata absent; palp attached distally; palp article 2 broad, article 3 with subparallel margins or distally tapered. Maxilla 1 outer plate setal-teeth smooth, at least one inner row setal-tooth absent; palp absent.
Maxilliped inner plate absent
; outer plate medium size;
palp 3-articulate (article 4 absent)
.
Gnathopod 1 ischium smaller than propodus
; corner of palm with simple robust seta or without any robust seta. Gnathopod 2 palm obtuse.
Epimeron 3 posteroventral corner broadly rounded
. Uropod 3 biramous.
Remarks.
With the new species described from the boreal eastern North Pacific and the tropical western South Pacific and the reassignment of some species to
Ultimachelium
, the distribution of the previously bipolar genus
Pachychelium
is changed significantly. The sister taxon of
Pachychelium
appears to be
Ultimachelium
. The genera differ in the number of articles in the maxillipedal palp (article 4 absent in
Pachychelium
, large and well developed in
Ultimachelium
) and in epimeron 3 which has a broadly rounded posteroventral corner in
Pachychelium
, projecting and narrowly rounded in
Ultimachelium
.
Species composition.
Pachychelium davidis
Stephensen, 1925
;
P. fucaensis
sp. nov.
;
P. tropicalis
sp. nov.
Pachychelium antarcticum
Schellenberg, 1926
, is regarded as an unidentifiable taxon.