Planche 1 issued from : E. Suarez-Morales & V.V. Ivanenko in Arctic, 2004, 57 (1). [p.43, Fig.8].
Female (from outside Trondheimsfjord, Norway): A, cephalothorax (lateral); B, 5th pedigerous somite and genital double-somite (lateral); C, idem (ventral); D, 2nd, 3rd and 4th pedigerous somites (4th separated; lateral); E, last part of urosome and caudal rami.

Planche 2 issued from : E. Suarez-Morales & V.V. Ivanenko in Arctic, 2004, 57 (1). [p.43, Fig.9].
Female: A, cephalic area with part of A1 (dorsal); B, exopod of P1; C, two distal segments of exopod of P2, P3 or P4; D, urosome (lateral, another specimen); E, cephalic area (dorsal, from second specimen); F, idem (ventral; from the first specimen).

Planche 3 issued from : E. Suarez-Morales & V.V. Ivanenko in Arctic, 2004, 57 (1). [p.42, Table 1].
Comparison of taxonomic features and morphometry in females of selected species of Monstrillopsis.
A1 = antennule; AN = anal somite; CT = cephalothorax; FP = 1st pediger; GS = genital double-somite; LA = last antennular segment; TL = total length; UR = urosome. All ratios are presented in percentage form.

Planche 4 issued from : G.O. Sars in An Account of the Crustacea of Norway, with short descriptions and figures of all the species, 1921 a, 8. [Pl. XIV]. As Monstrillopsis dubia.
Female and Male (from Bejan: outside of Trondhjem Fjord).
Female: Nota: Cephalic segment exceeding the remaining part of the body by 1/3 of its length.
Eye very conspicuous, with dark pigment and all 3 lenses well developed.
A1 4-segmented, exceeding somewhat in length 1/3 of the cephalic segment; the last segment is fully as long as the other 3 combined, none of the setae ramified.
Oral tubule well marked, located near the frontal part of the head.
natatory legs with the exopod considerably longer than endopod; P5 rather narrow at the base, but considerably widdening towards the end, which is produced to a conical lappet, across the base of which 3 slender setae are attached, inner edge of the leg produced to a similar lappet, which is quite smooth.
Genital segment a little longer than the other 2 segments combined.
Ovigerous spines of moderate length.
Anal segment somewhat flattened and sharply defined from the rather small middle segment.
Caudal rami exceeding somewhat in length the 2 preceeding segments combined, slightly divergent, each ramus with 4 setae, 1 about in the middle of the outer edge, 2 at the apex, and 1 inside at some distance from the end.

Male: Nota: Cephalic segment somewhat club-shaped, and scarcely exceeding half the length of the body.
Eye more developed than in female, with the ventral lens prominent and highly refractive.
A1 5-segmented, considerably exceeding half the length of the cephalic segment; the last segment very mobile segment abruptly attenuated distally.
Abdomen 4-segmented, the first of which is produced below to a rather large copulative appendage divided at the end into 2 diverging subcylindral rami.

Planche 5 Issued from : E. Suarez-Morales, A. Bello-Smith & S. Palma in Zool. Anz., 2006, 245. [p.103, Table 1]. Structural characteristics.
Morphological characters for comparative morphology of the species assigned to the genus Monstrillopsis by different authorities. See : dubia, M. fosshageni, M. reticulata, M. sarsi, Cymbasoma gracilis, M. ferrari, M. zernovi, M. angustipes, Monstrillopsis sp.

Key for the identification of the currently known species of Monstrillopsis (female only) after Suarez-Morales & al. (2006, p.105):
1 - Outer (exopodal) lobe of P5 with distal elongation; last antennular segment relatively long, more than 50% of A1 length; large species (more than 3 mm) ..... 2.
2 - Genital doubble-somite relatively long, representing more than 55% of urosome length; A1 length about or less than 20% of total bopdy length, element 1 (on 1st segment) reduced; caudal rami elongate 2.2 times longer than wide.