Species Card of Copepod
Calanoida ( Order )
    Clausocalanoidea ( Superfamily )
        Scolecitrichidae ( Family )
            Pseudoamallothrix ( Genus )
Pseudoamallothrix obtusifrons  (Sars, 1905)   (F)
Syn.: Amallophora obtusifrons Sars, 1905 b (p.22, Rem.F); Pearson, 1906 (p.17, Rem.); Bradford, 1973 (p.143); Bradford & al., 1983 (p.78, Rem.); Lapernat, 2000 (tabl.3, 4);
Amallothrix obtusifrons : Sars, 1925 (p.179, figs.F, [no M]); Sewell, 1929 (p.221, Rem.); Rose, 1933 a (p.153, figs.F, [no M]); Wilson, 1942 a (p.171); Lysholm & al., 1945 (p.28); Sewell, 1948 (p.349, 502, 546, 550, 567); C.B. Wilson, 1942 a (p.171, fig.F); 1950 (p.162, figs.F); Grice, 1963 a (p.495); Grice & Hulsemann, 1967 (p.16); Björnberg, 1973 (p.384); Deevey & Brooks, 1977 (p.256, tab.2, Station "S"); Lozano Soldevilla & al., 1988 (p.58); Bradford-Grieve & al., 1999 (p.881, 931, figs.F); Razouls & al., 2000 (p.343, Appendix); Vives & Shmeleva, 2007 (p.736, figs.F,M, Rem.);
? Scolecithricella curticauda A. Scott, 1909 (p.94, figs.F);
Scolecithrix obtusifrons : van Breemen, 1908 a (p.75); no Farran, 1908 b (p.54, Rem.);
? Scolecithricella tydemani A. Scott, 1909 (p.93, figs.F); Wilson, 1932 (p.79);
no Scaphocalanus obtusifrons : With, 1915 (p.194); Lysholm & Nordgaard, 1921 (p.21);
Scolecithricella obtusifrons : Park, 1980 (p.66, figs.F, Rem.); Park & Ferrari, 2009 (p.143, Table 4, Appendix 1, biogeography); no A. Scott, 1909 (p.92, figs.F); ? Guangshan & Honglin, 1984 (p.118, tab.);
no Scolecithrix emarginata Farran, 1905 (p.36, figs.F);
? Amallothrix optusiformis : Dowidar & El-Maghraby, 1970 (p.267);
Scolecithricella (Amallothrix) obtusifrons : Björnberg, 1973 (p.332)
Vyshkvartzeva, 2000 (p.228, Rem.)
Species Pseudoamallothrix obtusifrons - Plate 1 of morphological figuresissued from : T. Park in Antarct. Res. Ser. Washington, 1980, 31 (2). [p.65, Fig.21]. As Scolecithricella obtusifrons.
Female: a, forehead (lateral); b, last thoracic segments and urosome (lateral left side); c, genital segment (lateral left side); d, rostrum (anterior); e, A2; f, Md; g, Mx1; h, distal part of Mx2; i, Mxp; j, P1 (anterior); k, P2 (posterior); l, P3 without two distal exopodal segments (oosterior); m, P5 (posterior).

Nota: Articulation suture separing 4th and 5th metasomal segments almost complete. Ventral margin of genital segment posterior to genital opening not strongly curved (as in P. emarginata); spermathecal vesicle (fig.21c) not fully inflated and without a separate distal sac

Species Pseudoamallothrix obtusifrons - Plate 2 of morphological figuresIssued from : G.O. Sars in Résult. Camp. Scient. Prince Albert I, 69, pls.1-127 (1924). [Pl.L, figs.1-14]. As Scolecithrix obtusifrons.
Female (NE Atlantic): 1, habitus (dorsal); 2, idem (lateral left side); 3, rostrum; 4, rostral filament (enlarged); 5, A2; 6, Md; 7, Mx1; 8, Mx2; 9, Mxp; 10, P1; 11, P2; 12, P3; 13, endopodal segments of P4; 14, P5.

Nota Female:
- Head and 1st pedigerous segment fused, 4th and 5 th thoracic segments fused.
- Rostrum relatively strong and short, with attached 2 stong filaments ribbon-like, ending by 2 little pointed.
- Posterolateral corners of the last thoracic segment short and obtusely rounded.
- Urosome length about 1/4 of prosome.
- Genital segment about as long as the two following segments together; slightly swollen ventrally and anteriorly in the segment.
- Caudal rami slightly longer than wide , slightly obliquely truncate at apex.
- A1 shorter than the body, extens about to the anal segment.
- A2 endopod longer and more thick than exopod.
- Md strong, gnathobase with number teeth closeup.
- Mx1 with the inner lobe 1 (arthrite) orotruded and narrow.
- Mx2 of the same structure than in Amallothrix gracilis with the same sensory filaments.
- Mxp slender, distal part about as long as the 2nd basal segment.
- Swimming legs barely unlike those Amallothrix gracilis.
- P5 distinctly bisegmented with the distal segment more than 2 times as long as the proximal and slightly narrowed in the middle.; extremity conical with 3 spines: 1 inner very strong , 1 little at apex, and generally a little tooth outside, and 1 more little external. Surface of the segments without rows of hairs.

NZ: 10 + 1 doubtful

Distribution map of Pseudoamallothrix obtusifrons by geographical zones
Antarct. (SE Atlant., S Pacif.), sub-Antarct. (Indian, SE Pacif.), off NW Cape Verde Is., Canary Is., Ibero-moroccan Bay, ? E Medit. (Alexandria), Azores, Bay of Biscay, off Bermuda: Station "S" (32°10'N, 64°30'W), Sargasso Sea, Woods Hole, W Indian, Philippines, Pacif. (W equatorial), Galapagos, Peru, N Chile
N: 16
(1) F: 5,6; (523) F: 6,35-5,25; {F: 5,25-6,35}
Rem.: Bathypelagic. Sargasso Sea: 1000-2000 m (Deevey & Brooks, 1977, station "S");
Certain locality records are questionable because of the possible confusion with Pseudoamallothrix emarginata. For Park (1980, p.67) the two species are distinguishable by the form of the spermatheca and details of the Md, Mx1 and Mx2.
Last update : 21/03/2017
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 Any use of this site for a publication will be mentioned with the following reference :

Razouls C., Desreumaux N., Kouwenberg J. and de Bovée F., 2005-2024. - Biodiversity of Marine Planktonic Copepods (morphology, geographical distribution and biological data). Sorbonne University, CNRS. Available at http://copepodes.obs-banyuls.fr/en [Accessed May 29, 2024]

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