Eudorella paramonodon, Mühlenhardt-Siegel, 2025

Eudorella paramonodon sp. nov.

( Figures 5–8 View FIGURE 5 View FIGURE 6 View FIGURE 7 View FIGURE 8 )

Material:

Holotype: 1 non-ovigerous female ( ZMH K 64945 View Materials ) ( 15 July 2009); SW Atlantic, Argentine Basin, FS “Meteor”cruise Me 79/1, station #533, 36° 00.20'S 49° 01.96'W, 4602 m depth; gear: EBS. GoogleMaps

Paratypes:

Argentine Basin:

# 533—EBS: 1 subadult male with developing pleopods ( 5.2 mm long, dissected, ZMH K 64946 View Materials ) .

#533—EBS: 1 non-ovigerous female, damaged (ZMH K 64971 View Materials ).

# 534—EBS: 1 juvenile male (no dorsal tooth), 1 adult male, pleon missing (pleonite 3 and onwards) ( ZMH K 64972 View Materials ) .

Brazil Basin:

#604—EBS: 1 non-ovigerous female (front part damaged) (ZMH K 64973 View Materials ).

#609—EBS: 1 manca (ZMH K 64974 View Materials ).

Etymology. — The new species is named “ paramonodon ” because of its similar appearance to E. monodon Calman, 1912 .

Diagnosis.—Anterior margin of carapace with tooth formula: 7 up, 0 down (above antennal notch), 2 down (below antennal notch); second article of the A1 peduncle not dilated.

Description.—Based on holotype ( Figure 5 View FIGURE 5 ), non-ovigerous female, 5.3 mm long ( ZMH K 64945 View Materials ). Carapace little shorter (0.9 times) than free thoracic segments, with a single tooth middorsally immediately behind frontal lobe; pseudorostral lobes short, directed upwards; siphonal tube not protruding; ocular lobe reduced, eye lenses missing.

Antennal notch small, anterolateral tooth not pronounced; anterior margin of carapace with tooth formula: 6 up, 0 down (above antennal notch), 2 down (below antennal notch); anteroventral margin serrate ( Figure 8 View FIGURE 8 ); integument whitish. Five free thoracic segments visible, the first smallest.

Pleon 1.3 times longer than carapace plus free thoracic segments.

Pleotelson 1.4 times longer than wide.

Appendages: subadult male, paratype, 5.2 mm long ( ZMH K 64946 View Materials ) .

Antenna 1 ( Fig. 6 View FIGURE 6 , A 1 View FIGURE 1 ): relative length of peduncle articles 1 to 3 not given, article 1 broken during dissection, article 2 about as long as article 3; accessory flagellum 0.8 times as long as basal article of main flagellum, with 3 simple setae terminally; main flagellum 3-articulated.

Antenna 2 ( Fig. 6 View FIGURE 6 , A 2 View FIGURE 2 )

Maxilliped 2 ( Fig. 6 View FIGURE 6 , Mxp2): B/R ratio 0.4, relative length of articles I to D: 10/32/26/21/11; basis with 2 pappose setae; ischium unarmed; merus with one plumose seta; carpus with 3 plumose setae and 8 simple setae; propodus with one long plumose seta and 11 simple setae; dactylus with one terminal and 3 sub terminal simple setae.

Maxilliped 3 ( Fig. 6 View FIGURE 6 , Mxp3): B/R ratio 0.9, relative length of articles I to D: 7/21/31/19/21; basis distally widened, with 3 long plumose setae on extension; ischium with one pappose seta; merus with one long pappose seta on outer distal edge, 3 pappose setae along inner margin; carpus with 8 pappose setae along inner margin; propodus with 4 pappose setae on distal margin; dactylus with one terminal and 4 sub terminal simple setae, one pappose seta subterminally; exopod present.

Pereiopod 1 ( Fig. 6 View FIGURE 6 , P 1 View FIGURE 1 ): B/R ratio 0.7, relative length of articles I to D: 11/18/24/28/19; basis with 8 teeth along inner margin, 7 pappose setae, one simple seta on inner distal corner, 2 pappose setae on outer distal edge; ischium with one simple seta; merus with 2 simple setae, one pappose seta; carpus with 4 simple setae; propodus with 7 simple setae; dactylus with one terminal simple seta, 5 simple setae along inner margin, 3 short simple setae on outer margin; exopod present.

Pereiopod 2 ( Fig. 6 View FIGURE 6 , P 2 View FIGURE 2 ): B/R ratio 1, relative length of articles I to D: 0/28/33/13/25; basis with 4 pappose and 2 simple setae; ischium fused to basis; merus with one pappose seta, 2 short simple setae; carpus with one simple seta; propodus unarmed; dactylus with 9 simple setae; exopod present.

Pereiopod 3 ( Fig.7 View FIGURE 7 , P 3 View FIGURE 3 ): B/R ratio 1.7, relative length of articles I to D: 15/28/28/20/9; basis with 6 simple setae, one pappose seta on distal margin; ischium with one pappose seta; merus with one simple and one pappose seta; carpus with 3 simple setae; propodus with one simple seta on outer distal corner; dactylus with one strong simple seta terminally; exopod present.

Pereiopod 4 ( Fig. 7 View FIGURE 7 , P 4 View FIGURE 4 ): B/R ratio 1.8, relative length of articles I to D: 18/29/24/22/7; basis with 5 simple setae; ischium unarmed; merus with one pappose and one simple seta; carpus with one simple seta and 2 pappose setae; propodus with 2 simple setae; dactylus with 2 simple seta terminally, exopod present.

Pereiopod 5 ( Fig. 7 View FIGURE 7 , P 5 View FIGURE 5 ): B/R ratio not given, basis damaged during dissection, relative length of articles I to D: 21/21/29/21/7; basis, ischium and merus unarmed; carpus with one pappose seta, 3 simple setae on distal margin; propodus unarmed; dactylus with one strong terminal seta.

Uropods ( Fig. 7 U View FIGURE 7 ), peduncle 0.9 times as long as pleonite 6, subequal in length to basal article of endopod; exopod slightly shorter than endopod; endopod 2 articulated, basal article 3.4 times longer than second article, with 8 (one broken in the present specimen) cuspidate setae along inner margin; second article with 3 cuspidate setae along inner margin, one simple seta terminally.

Distribution: Argentine and Brazil Basin, 4601 to 5180 m.

Remarks: The specimens assigned here to Eudorella paramonodon sp. nov. are in poor condition, but the arrangements of the teeth on the anterior margin of the carapace indicates that they all belong to the same species ( Fig. 8 View FIGURE 8 ).

There is only one known Eudorella species with a mediodorsal tooth on the carapace behind the exhalant hole, E. monodon Calman, 1912 from the Gulf of Mexico. Calman (1912) stated for this species “Anterior margin most nearly resembling that of E. hirsuta Sars , but the antero-lateral tooth is more prominent and the serrations on the upper part of the margin (anterior margin of the pseudorostral plate) point downward.

Among the present specimens is only one undamaged non-ovigerous female, the holotype, with a dorsal anteriorly curved tooth as in E. monodon , but the antero-lateral serration ( Figure 8 View FIGURE 8 ) is different: in E. monodon the more dorsal 4 spines are directing downward, in the present specimens they are pointing forward. In E. monodon the second article of the A1 peduncle is dilated, in the present specimens it is not. There is 1 species, Eudorella helenae Brito & Serejo, 2023 , from the Brazil Basin ( 25–392 m depth), which is not conspecific with the new species because the terminal seta of the uropod endopod is fused to the last article, in the new species it is articulated, and the middorsal tooth on the carapace is located before the frontal fissure in E. helenae , but it is located behind the frontal lobe fissure in the new species.

In both species, E. paramonodon sp. nov. and E. monodon , the middorsal tooth is located at one-third of the carapace just behind the frontal lobe, whereas in E. truncatula and E. helenae this tooth is contiguous to the respiratory opening.