Eurotanais seilacheri, Sanchez-Garcia & Penalver & Bird & Perrichot & Delclos, 2016

Sanchez-Garcia, Alba, Penalver, Enrique, Bird, Graham J., Perrichot, Vincent & Delclos, Xavier, 2016, Palaeobiology of tanaidaceans (Crustacea: Peracarida) from Cretaceous ambers: extending the scarce fossil record of a diverse peracarid group, Zoological Journal of the Linnean Society 178 (3), pp. 492-522 : 501-510

EUROTANAIS SEILACHERI SANCHEZ- GARCIA, PE NALVER ~ & PERRICHOT SP. NOV. ( FIG. 4 )

Etymology

Named in memory of Professor Adolf Seilacher (1925 – 2014), for his outstanding contributions to evolutionary and ecological palaeobiology, the study of trace fossils, and his well-known work on the Ediacaran assemblages.

Type material

Holotype and only known specimen IGR.GAR-61, ♂. Incomplete and ventrolaterally exposed. Body proportions cannot be easily measured as the dorsal view is oblique to the amber surface. The specimen shows some body areas that are blackened and somewhat altered as a result of fossilization, or hidden and poorly visible owing to the fossilization position (mostly the cephalothorax outline, eyes, antennae, and mouthparts). The pereon is cut diagonally, with the distal portion not preserved (also including pleopods, pleotelson, and uropods). Most pereopods are missing or badly preserved. It is preserved in syninclusion with fragments of an undetermined insect.

Occurrence

Late Cretaceous (Turonian) Vendean amber; La Robiniere, departmental road D32, about 2.5 km south-west of La Garnache, department of Vendee, north-western France ( Perrichot & Neraudeau, 2014).

Diagnosis

As for the genus with the following additions. Male. Antennule at least with ten articles, with numerous aesthetascs. Antenna with subequal articles, never square. Cheliped with inner surface of propodus bearing comb of about six long thin setae. Blunt tooth of cheliped fixed finger with an acuminate process, bearing three distinctive setae. Female. Unknown.

Description

Body ( Fig. 4A, B ) medium-sized, estimated total length 1.53 mm, width not measurable; subcylindrical, slightly flattened dorsoventrally. All observed setae simple.

Cephalothorax morphology and measurements uncertain because of the preservation; about 0.23 times total body length as estimated, and longer than combined length of pereonites 1 – 3, width not measurable. Rostrum and eyes not visible.

Pereon rather short, about 0.48 times total body length as estimated, width not measurable. All pereonites wider than long; pereonites 1 – 3 subequal in length; pereonites 4 – 6 the longest, subequal in length, each about 1.66 times the length of each pereonite 1 – 3.

Pleon and pleotelson not preserved.

Antennule ( Fig. 4D ) at least ten-articled (proximal area poorly visible), less slender than in E. pyrenaensis sp. nov., tapering distally, longer than cephalothorax as estimated (1.46 times); visible article 1 proximally concealed by cheliped, fairly stout, without visible setae; visible article 2 nearly twice as long as thick (1.84 times), fairly stout, without visible setae; article 3 about as long as thick, without visible setae; articles 4 – 9 slightly decreasing gradually in length and thickness towards the apex, with numerous aesthetascs on ventral margins; terminal article (article 10) 0.74 times the length of preceding article and thinner, 1.26 times as long as thick, bearing three short setae apically.

Antenna at least four-articled (proximal area poorly visible), approximately half the length of antennule and much thinner; visible article 1 almost completely concealed by cheliped, without visible setae; visible article 2 2.23 times longer than thick, without visible setae; visible article 3 1.31 times the length of preceding article, 2.98 times longer than thick, with one long outer seta distally; terminal article (visible article 4) only slightly longer than preceding article but thinner, 4.99 times longer than thick, bearing four short and four long unequal setae apically.

Mouthparts not visible.

Cheliped ( Fig. 4C ) robust; sclerite not visible; basis fairly robust, widening distally, 1.85 times longer than thick, 0.86 times the length of carpus, without visible setae; merus subtriangular, with up to three long setae ventrally; carpus rectangular, nearly twice as long as thick (1.90 times), slightly longer than propodus, without visible setae; propodus robust, more massive than carpus, fixed finger deflexed almost perpendicular to palm, with dactylus directed medially; inner surface of propodus bearing comb of at least six long thin setae becoming progressively longer ventrally, and one conspicuous seta near the base of fixed finger; fixed finger and dactylus unequal in length, widely separated at base forming a distinct gap between them (i.e. forcipate); fixed fin- ger with three conspicuous inner setae subdistally arising from a blunt tooth with an acuminate process, and one ventral seta medially, terminating in unguis; dactylus strongly developed, extending beyond fixed finger, 1.90 times the length of fixed finger, gradually curving, with rounded end, unguis not visible.

Pereopods with coxa present (visible on left pereopods 1 – 4); basis fairly slender and cylindrical on pereopods 1 – 3 to fairly robust and inflated on pereopods 4 – 6 (only visible at left pereopod 4); ischium short (visible on left pereopods 1 and 2); merus and carpus apparently subequal in size, not widening distally, propodus and dactylus measurements and details uncertain because of the preservation.

Pleopods not preserved. Uropods not preserved.

Remarks

As noted above, this species has the general appearance of the genus Eurotanais . The diagnostic shape of the cheliped – fixed finger with a prominent blunt tooth and unequally and widely separated from the dactylus, thereby forming a distinct gap between them – places E. seilacheri sp. nov. in this genus. Its form approaches that of extant leptocheliids such as Konarus Bamber, 2006 , Parakonarus Bird, 2011 , and Pseudoleptochelia Lang, 1973 (see Bamber, 2013), but the fixed finger is better developed than in those taxa; the forcipate nature and long dactylus also resemble those of the extant nototanaids Nototanais antarcticus (Hodgson, 1902) and Nototanais dimorphus (Beddard, 1886) .

The body and the cephalothorax morphology of the holotype are mostly opaque and can thus be seen only in profile. However, it is noticeable that the multi-articled antennule is well preserved, and has at least ten articles instead of the eight in E. terminator Sanchez-Garcıa, Pe nalver ~ & Delclos, 2015, and E. pyrenaensis sp. nov. Unfortunately, the pleon and uropods are not preserved at all, meaning that it is impossible to determine whether the individual possessed a plesiomorphic highly segmented uropod like that of E. pyrenaensis .

We originally considered placing the species in a new genus but decided that the specimen can be placed in Eurotanais pending the examination of any additional material. This is the only species known from Vendean amber (La Garnache) ascribable to the family Alavatanaidae .

FAMILY INCERTAE SEDIS

GENUS ARMADILLOPSIS SANCHEZ- GARCIA, PE NALVER ~ & PERRICHOT GEN. NOV

Type species

Armadillopsis rara Sanchez-Garcıa, Pe nalver ~ & Perrichot sp. nov. by monotypy.

Etymology

The generic name is a combination of armadill- (meaning ‘little armoured one’ and reflecting the similarity in shape to the isopod genus Armadillidium ) and the Greek suffix opsis (meaning, ‘sight, appearance’; thus ‘looking like’).

Diagnosis

Male. Body very small and stout, less than four times as long as wide. Cephalothorax subtriangular when viewed dorsally (ratio length/width close to 1). Eyes very large (> 26% of cephalothorax surface). Pereon very short (less than 0.4 times the body length), with pereonites 1 and 2 very short compared with its width (c. as long as pereopod basis width). Pleon greatly elongated, slightly longer than pereon (more than 0.4 times the body length), weakly demarcated with five free pleonites about the same general size and appearance as pereonites 4 – 6. Antennule with at least six articles. Mouthparts not reduced. Cheliped somewhat robust; fixed finger and dactylus unequally developed, widely separated at base forming a distinct gap between them (i.e. forcipate); inner surface of propodus bearing comb of about nine to ten short, thick setae; carpus short (ratio length/width close to 1). Pereopod coxa present in all pereopods; pereopods 4 – 6 heavily armed with straight spines, with dactylus plus unguis very long (as in pereopods 1 – 3), not claw-like. Uropod biramous, relatively long and stout, endopod about 1.3 times the length of exopod; endopod and exopod with two articles; exopod reaching half the length of distal endopodal article. Female. Unknown.

ARMADILLOPSIS RARA SANCHEZ- GARCIA, PE NALVER ~ & PERRICHOT SP. NOV. ( FIGS 5 , 6 )

Etymology

Named to reflect the peculiar morphology of this species and the problems in assigning it to a family (from the Latin adjective rara meaning ‘peculiar’).

Type material

Holotype and only known specimen MNHN. F.A51531, ♂. The specimen, preserved with high fidelity, is embedded in a small, dark-orange piece of amber, slightly clouded by organic debris. The sample belongs to the piece #FOU-6, with syninclusions detailed above.

Occurrence

Middle Cenomanian Pyrenean amber, near Fourtou village, Aude department, north-eastern Pyrenees, southern France ( Girard et al., 2013).

Diagnosis

As the genus is monotypic so far, the diagnosis is identical to that of the genus.

Description

Body ( Figs 5A , 6A ) very small, total length 0.64 mm; stout and compact, 3.94 times longer than wide; subcylindrical, slightly flattened dorsoventrally. All observed setae simple.

Cephalothorax ( Fig. 5B ) subtriangular when viewed dorsally, gradually narrowing anteriorly (i.e. without a lateral constriction), slightly wider than long (ratio length/width 0.94); 0.27 times total body length, nearly as long as combined length of pereonites 1 – 5, lateral margins convex, posterior margin rounded. Rostrum absent. Eyes well developed, very large, diameter 0.44 times the cephalothorax length, slightly bulging, anterolaterally placed on cephalothorax.

Pereon ( Fig. 6B ) very short, 0.35 times total body length. All pereonites wider than long, with weakly convex lateral margins when viewed dorsally, rectangular when viewed laterally, tergite and sternite overlapping with succeeding pereonite; combined lengths of pereonites 1 – 3 significantly shorter than pereonites 4 – 6, 0.34 times pereon length; pereonites 1 and 2 much shorter than subsequent pereonites, reduced to a band as long as the width of pereopod basis, 7.15 times wider than long; pereonite 3 slightly longer than preceding pereonites, 1.43 times the length of pereonite 1; pereonites 4 – 6 the longest, subequal in size, about 1.54 times the length of pereonite 1, 3.85 times wider than long.

Pleon ( Fig. 5D ) greatly elongated, slightly longer than pereon, 0.45 times total body length, weakly demarcated, showing continuity with the pereon, with five free subequal pleonites each bearing pairs of pleopods; pleonites about the same general size and appearance as pereonites 4 – 6, progressively narrower posteriorly. Pleotelson short, as long as last pleonite, gradually tapering distally, with somewhat acute posterior margin.

Antennule ( Fig. 6B ) at least six-articled (proximal area poorly visible), fairly stout at base, tapering distally although the general appearance of the articles is fairly stout (exact measurements of thickness are not possible owing to preservation), nearly as long as cephalothorax (0.97 times); article 1 fairly stout, about 0.57 times the length of antennule, expanded dorsally, with one long outer seta distally; article 2 about 0.23 times the length of article 1 (measurement possibly underestimated), with one long outer seta distally; articles 3 – 6 subequal in length, decreasing in thickness towards the apex, but not easily measurable because of its foreshortened position; articles 3 and 4 with one outer seta subdistally; terminal article (article 6) with up to six long and quite thick setae apically.

Antenna poorly visible, at least four-articled, shorter than antennule and much thinner; proximal articles without visible setae; terminal article shortest, with four long setae apically.

Maxilliped endites and basis poorly visible. Endites unfused, without visible setae. Maxilliped palp articles not clearly discernible, relatively stout; terminal article with inner row of four thick setae distally.

Cheliped ( Fig. 6B ) somewhat robust; sclerite not visible; basis rounded in lateral view, about 1.72 times longer than thick, 1.23 times the length of carpus, without visible setae; merus subtriangular, well developed, without visible setae; carpus short, rounded in lateral view, 1.15 times longer than thick, slightly shorter than propodus (0.96 times), without visible setae; propodus with fixed finger and dactylus unequal in length, widely separated at base forming a distinct gap between them (i.e. forcipate); inner surface of propodus bearing comb of about nine to ten short thick setae; fixed finger with slightly convex incisive margin, without visible setae, terminating in unguis; dactylus somewhat developed, slightly extending beyond fixed finger, 1.57 times the length of fixed finger, gradually curving, with extremely acute end, unguis not visible.

Pereopods 1 – 3 badly preserved, overall as pereopods 4 – 6 (see description below) except slender basis and setation not observed.

Pereopods 4 – 6 ( Fig. 5C ) sturdier than pereopods 1 – 3; coxa present; basis fairly robust, more inflated than in pereopods 1 – 3, about 2.59 times longer than wide, about as long as merus and carpus combined, without visible setae; ischium well developed, bearing up to two short and thin setae; merus and carpus subequal in size, widening distally; merus with two almost straight long spines distally; carpus with three to five almost straight long spines distally; propodus longer than carpus, tapering distally, with three almost straight long spines distally; dactylus and unguis not fused, not claw-like, slightly curved, and very long, combined length about as long as propodus (1.06 times).

Pleopods ( Fig. 5D ) all alike; basal article rounded, without visible setae; endopod and exopod subovate, with long terminal setae difficult to enumerate as preserved, bundled together under the pleon.

Uropod ( Figs 5E , 6C ) biramous, the endopod about 1.27 times the length of exopod; basal article subtriangular, widening distally, fairly short and stout, slightly shorter than exopod article 1, without visible setae. Endopod relatively long and stout, with two subequal articles; article 1 with one inner seta distally, article 2 ending with up to five long setae. Exopod relatively long and stout, just slightly thinner than endopod, reaching half the length of distal endopodal article, with two subequal articles; article 1 slightly shorter than endopod article 1, with two outer setae distally, article 2 ending with one long visible seta.

Remarks

The unique combination of its at least six-articled antennule, cheliped with inner propodal comb of about nine to ten thick spines at dactylus insertion, straight and enlarged simple spines on pereopods 4 – 6, dactylus plus unguis length subequal to the propodus length in all pereopods, and stout uropod with both rami two-articled, justify the erection of a new genus for this morphotype, but make the attribution to a suprageneric taxon somewhat difficult.

Besides the above-mentioned characters, a highly characteristic body shape marks out this taxon from most other species. Armadillopsis rara gen. et sp. nov. is remarkable in possessing an almost oniscoid body. i.e. a weakly demarcated pleon with pleonites about the same general size and appearance as pereonites 4 – 6, which gives the body a continuous appearance between pereon and pleon. The enlarged pleon, somewhat longer than the pereon and progressively narrower posteriorly, amounts to nearly half of the body length, whereas the pereon has pereonites 1 – 2 strongly reduced.

In this respect Arm. rara closely resembles some described extant males of the family Paratanaidae Lang, 1949 , and particularly the genus Paratanais Dana, 1852 (for which the male morph is known for 11 species, see table 1, p. 66 in Morales-Nu nez ~ & Heard, 2014), along with (1) its small body, (2) relatively shorter pereonites, (3) pleonites more developed, of almost similar size and appearance as pereonites, (4) very large and well-developed eyes (> 20% of cephalothorax), (5) antennule with more than five articles (following Larsen, 2001), (6) dactylus and unguis of pereopods 4 – 6 not modified to a claw, and (7) pleopods well developed, with long setae. Unlike paratanaid males, Arm. rara has welldeveloped mouthparts (vs. degenerate), and unequal cheliped fingers (vs. with relatively short and small fingers). In addition, Arm. rara has not been recorded with antennulae densely packed with aesthetascs, but this character can be easily overlooked. Regarding the variable uropodal configuration within the paratanaidins (other genera as well as Paratanais ), the presence of stouter uropods with both rami two-articled appears to distinguish Arm. rara from most paratanaids ( Bird, 2011).

Lastly, the extant family Nototanaidae Sieg, 1976 , includes some minute male forms with a combination of characters that largely agree with those found in our specimen, and some nototanaid males probably represent the smallest known adult tanaidaceans (less than 0.5 mm; Heard, Hansknecht & Larsen, 2004). Armadillopsis rara bears a particularly close superficial similarity to the extant unidentified taxa ‘Nototanaid? sp. A’ illustrated and tentatively placed in the Nototanaidae by Heard et al. (2004), in having (1) a very short, minute, compressed body, (2) eyes very large and well developed, (3) antennule with six apparent articles, with basal article massive and inflated, (4) cheliped not overly developed, (5) all pereopods with coxa, (5) pereopods with dactylus and unguis not fused into a claw, (6) uropod with both rami biarticulated, and (7) uropodal exopod elongated, about three-quarters length of endopod, distinctly longer than article 1 of endopod. Both the presence of coxa and the unfused dactylus – unguis in pereopods 4 – 6 are rare amongst the Nototanaidae . Armadillopsis rara differs further in the (apparent) absence of antennular aesthetascs, stout pereopods (vs. slender and delicate), well-developed mouthparts (vs. degenerate), unequal cheliped fixed finger and dactylus (vs. relatively short and small), and stout uropods (vs. slender).

The morphological convergence between some Nototanaidae and Paratanaidae minute males was described in Heard et al. (2004). Usually, highly dimorphic natatory Recent males are similar in body shape and have little differentiation between pereon and pleon segments, as the pleon is more ‘important’ for supporting the larger pleopods needed for the males to swim about and find females.

Thus, we have recognized this form as a distinct taxon that might be convergent with some paratanaid and nototanaid male forms.

GENUS TYTTHOTANAIS SANCHEZ- GARCIA, PE NALVER ~ & PERRICHOT GEN. NOV

Type species

Tytthotanais tenvis Sanchez-Garcıa, Pe nalver ~ & Perrichot sp. nov. by monotypy.

Etymology

The generic name is a combination of the Greek word tytthos, meaning ‘small’ or ‘young’, and Tanais , a genus name used widely as a suffix in the Tanaidomorpha .

Diagnosis

Male. Unknown. Female. Body slender, about seven times as long as wide. Cephalothorax suboval when viewed dorsally (much longer than wide) with pointed rostrum. Eyes large (<9% of cephalothorax surface). Pereon rather short (about 0.5 times the body length). Pleon rather short (less than 0.3 times the body length); pleonites with one large lateral seta on each side. Antennule with four articles. Cheliped not robust; fixed finger and dactylus subequally developed, not widely separated at base, without forming a distinct gap between them (i.e. nonforcipate); carpus relatively short (ratio length/width close to 2). Uropod biramous, very short and thin, endopod about 1.5 times the length of exopod; endopod and exopod with two articles; exopod not reaching half the length of distal endopodal article.

TYTTHOTANAIS TENVIS SANCHEZ- GARCIA, PE NALVER ~ & PERRICHOT SP. NOV. ( FIGS 7 , 8 )

Etymology

Named after the delicate appearance of this species (from the Latin adjective tenvis meaning ‘thin’ or ‘slender’).

Type material

Holotype and only known specimen MNHN.F.A51530, ♀. The specimen, nearly complete and with some parts hidden or poorly visible, is embedded in a small piece of clear orange amber. The distal article of the right antennule is missing and the mouthparts and antennae are concealed by chelipeds and antennulae. Most pereopods are badly preserved or hidden and the setation pattern is difficult to discern and so could easily be overlooked. Clearing of the pleon cuticle allowed observation of the pleopods. The sample belongs to the amber piece #FOU-6, with syninclusions detailed above.

Occurrence

Middle Cenomanian Pyrenean amber, near Fourtou village, Aude department, north-eastern Pyrenees, southern France ( Girard et al., 2013).

Diagnosis

As the genus is monotypic so far, the diagnosis is identical to that of the genus.

Description

Body ( Fig. 7A, C ) small, total length 1.00 mm; slen- der, 7.05 times longer than wide; subcylindrical, slightly flattened dorsoventrally. All observed setae simple.

Cephalothorax ( Fig. 8A, D ) suboval when viewed dorsally, gradually narrowing anteriorly (i.e. without a lateral constriction), 1.41 times longer than its maximum width; 0.27 times total body length, nearly as long as combined length of pereonites 1 – 4; lateral margins slightly convex, posterior margin rounded, laterally swollen. Rostrum slightly pointed ( Fig. 8D ). Eyes well developed, large, diameter 0.24 times the cephalothorax length, slightly bulging, with deep emargination on anterior margin to accommodate antennule, anterolaterally placed on cephalothorax. One short stiff seta is visible on each side behind the posterior margin eye.

Pereon rather short, 0.50 times total body length. All pereonites wider than long, with weakly convex lateral margins when viewed dorsally (most probably because of preservation); pereonites 1 – 3 subequal in size, about 2.77 times wider than long; pereonites 4 – 6 the longest, subequal in size, about 1.34 times wider than long, each about 1.75 times the length of each of pereonites 1 – 3; pereonite 6 widening proximally to accommodate pleon.

Pleon ( Fig. 8E ) rather short, 0.27 times total body length, slightly wider than pereon, with five free subequal pleonites each bearing pairs of pleopods; all pleonites subequal in size, each about 0.31 times the length of each of pereonites 4 – 6, about 5.21 times wider than long, with one large lateral seta on each side ( Fig. 8C ). Pleotelson subequal in length to that of three pleonites together, gradually tapering distally, with slightly acute posterior margin.

Antennule ( Fig. 8A, D ) four-articled, fairly slen- der, tapering distally, relatively short, 0.80 times the length of cephalothorax; article 1 just over half of total antennule length (0.59 times), 2.87 times longer than thick, slightly expanded laterally at cephalothorax insertion, with two outer setae dis- tally; article 2 0.28 times the length of article 1, slightly longer than thick (1.13 times), with two outer setae distally; article 3 slightly shorter than preceding article (0.95 times) but thinner, with one inner seta distally; terminal article (article 4) half the length of preceding article (0.51 times), about as long as thick (1.06 times), with apical setae not visible.

Antenna and mouthparts not visible.

Cheliped ( Figs 7B , 8A, B ) not robust; sclerite not visible; basis measurements and details uncertain because of the preservation; merus not visible; carpus relatively short and slender, 1.77 times longer than thick, about as long as propodus (1.03 times), with two long ventral setae distally; propodus not delicate; fixed finger and dactylus subequal in length, without forming a distinct gap between them at their base (i.e. nonforcipate); fixed finger with slightly convex incisive margin, with two long inner setae subdistally and one ventral seta subdistally, terminating in unguis; dactylus thin, narrower than fixed finger, with cutting edge slightly curved, terminating in unguis.

Pereopods poorly visible.

Pleopods ( Fig. 8E ) all alike, basal article rounded; with long setae bundled together under the pleon.

Uropod ( Fig. 8E, F ) biramous, the endopod about 1.50 times the length of exopod; basal article fairly elongated, 2.65 times longer than thick, longer than endopod (1.20 times), without visible setae. Endopod very short and thin, with two subequal articles; article 1 with one outer seta distally; article 2 ending with four long setae. Exopod not reaching half the length of distal endopodal article, much thinner than endopod, with two subequal articles, article 1 without visible setae; article 2 ending with three long setae.

Remarks

This species is distinguished from the other taxa described and particularly Arc. turpis gen. et sp. nov. (see below), by a combination of characters, including its fairly slender habitus, more developed chelipeds, very short and thin uropods, and paratanaid-like lateral pleonal setae. Its affinities are uncertain but it resembles some extant females of the Paratanaidae , Nototanaidae , and Teleotanaidae Bamber, 2008 , and some genera of Leptognathiidae sensu Sieg, 1976 , such as Pseudoparatanais Lang, 1973 .

Figures

Figure 4. Holotype (IGR.GAR-61), male, of Eurotanais seilacheri sp. nov. A, ventrolateral view of the cephalothorax and anterior part of body (arrowheads point to the separation between antennular articles); B, camera lucida drawing in ventrolateral view; C, detail of left cheliped; D, detail of antenna and antennule; note the articles 4–9 showing aesthetascs (arrow). Scale bars: A, B = 0.2 mm; C, D = 0.1 mm.

Figure 5. Holotype (MNHN.F.A51531), male, of Armadillopsis rara gen. et sp. nov. A, ventral habitus; B, dorsal view of the cephalothorax and antennule; note the close-up of the row of setae on the inner surface of chelipedal propodus, magnified in the inset; C, detail of right pereopod 6 (arrowhead points to the tip of unguis); D, detail of pleopods; note the subovate pleopodal rami with long terminal setae; E, detail of right uropod. Scale bars: A = 0.2 mm; B, C = 0.1 mm; D = 0.05 mm; E = 0.025 mm.

Figure 6. Camera lucida drawings of the holotype (MNHN.F.A51531), male, of Armadillopsis rara gen. et sp. nov. A, ventral habitus (note the eyes and palps of maxilliped in grey); B, schematic ventrolateral view of the cephalothorax, chelipeds and anterior pereonites; C, detail of right uropod. Scale bars: A, B = 0.1 mm; C = 0.05 mm. Abbreviations: p4– p6, pereopods 4–6; pr1–pr4, pereonites 1–4.

Figure 7. Holotype (MNHN.F.A51530), female, of Tytthotanais tenvis gen. et sp. nov. A, camera lucida drawing in dorsal habitus (note the eyes in grey); B, camera lucida drawing of right cheliped in lateral view; C, dorsal habitus. Scale bars: A, C = 0.2 mm; B = 0.1 mm.

Figure 8. Holotype (MNHN.F.A51530), female, of Tytthotanais tenvis gen. et sp. nov. A, anterior part of body showing chelipeds and antennule in ventrolateral view; B, detail of right cheliped fixed finger in A; C, detail of left pleonal setae in E; D, dorsal view of the cephalothorax showing a slightly pointed rostrum; E, ventral view of the pleon; F, detail of uropod; note the two exopodal articles (arrowheads); G, detail of an anterior pereopod dactylus (arrowhead points to the tip of unguis). Scale bars: A–G = 0.1 mm.