Eurotanais pyrenaensis, 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 : 497-501

publication ID	https://doi.org/ 10.1111/zoj.12427
DOI	https://doi.org/10.5281/zenodo.10543860
persistent identifier	https://treatment.plazi.org/id/5824AB77-FF9D-DB34-FCE0-FD45FDFB5508
treatment provided by	Marcus
scientific name	Eurotanais pyrenaensis
status	SP. NOV.

Treatment

EUROTANAIS PYRENAENSIS View in CoL SANCHEZ- GARCIA, PE NALVER ~ & PERRICHOT SP. NOV. ( FIGS 2 View Figure 2 , 3 View Figure 3 )

Etymology

The specific epithet pyrenaensis is after the range of mountains in south-west Europe (natural border between France and Spain).

Material

Holotype MNHN.F.A51529a, ♂ (superbly preserved) and paratypes MNHN.F.A51529b, ♂ (superbly preserved) and MNHN.F.A51529c, ♂ (very incomplete; only antennulae, antennae, and some of the chelipeds are preserved). The darkened cuticle of the specimens makes resolving some detailed characters impossible with light microscopy. All type specimens are preserved as syninclusions in a small (greatest length 6.07 mm) dark-orange piece of amber. The sample was originally part of a single piece (#FOU-6) that was subsequently divided into four fragments for optimal study. Syninclusions comprised one Hemiptera , one Hymenoptera Falsiformicidae , one large undetermined Insecta, one Acari Stigmaeidae (A. Arillo, pers. comm.), and the tanaidaceans MNHN.F.A51530, MNHN.F.A51531, and

MNHN.F.A51532.

MNHN.F.A51532 matches the diagnosis of E. pyrenaensis for some characters. However, the specimen is highly degraded and preserved in brittle amber with multiple internal fractures that hinder examination, and we cannot attribute them to this species with full confidence.

Occurrence

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

Diagnosis

As for the genus with the following additions. Male. Cephalothorax subtriangular when viewed dorsally. Antennule with eight articles, with numerous aesthetascs. Antenna with subequal articles, never square. Blunt tooth of cheliped fixed finger bearing three distinctive setae. Pereopod basis with one long distal seta. Pereopod 1 much longer than following pereopods, with long dactylus plus unguis (not longer than propodus); pereopods 2 – 3 with dactylus plus unguis much shorter than in pereopod 1; pereopods 4 – 6 armed with weak spines, and with dactylus plus unguis slightly shorter and stouter than in pereopods 2 – 3. Uropod biramous; endopod about 9.3 times the length of exopod; endopod with six articles; exopod with two articles, reaching half the length of endopodal article 1. Female. Unknown.

Description

Based largely on the holotype MNHN.F.A51529a ( Figs 2B – E View Figure 2 , 3G View Figure 3 ) and the paratype MNHN.F.A51529b ( Fig. 3B – F View Figure 3 ); differences with the paratype MNHN.F.A51529c ( Fig. 3A View Figure 3 ) are noted .

Body ( Figs 2A – C View Figure 2 , 3C View Figure 3 ) medium-sized, total length around 1.16 – 1.25 mm, about 5.37 times as long as

wide; subcylindrical, slightly flattened dorsoventrally. All observed setae simple.

Cephalothorax subtriangular when viewed dorsally, gradually narrowing anteriorly (i.e. without a lateral constriction), 1.61 times longer than its maximum width; around 0.27 – 0.31 times total body length, longer than combined length of pereonites 1 – 4; posterior margin rounded, laterally swollen. Rostrum absent. Eyes ( Fig. 3D View Figure 3 ) well developed, large, diameter 0.20 times the cephalothorax length, slightly bulging, anterolaterally placed on cephalothorax.

Pereon rather short, around 0.42 – 0.45 times total body length. All pereonites wider than long, with fairly convex lateral margins when viewed dorsally, rectangular when viewed laterally; pereonite 1 shorter than pereonite 2, 4.02 times wider than long; pereonites 2 and 3 subequal in size, about 1.45 times the length of pereonite 1, 2.93 times wider than long; pereonites 4 – 6 the longest, subequal in size, 2.15 times the length of pereonite 1, nearly twice as wide as long (1.92 times).

Pleon rather short, about 0.27 times total body length, with five free subequal pleonites each bearing pairs of pleopods; pleonites slightly wider than pereonites but much shorter (each about 0.46 times the length of each pereonite 4 – 6), about 4.54 times wider than long. Pleotelson ( Fig. 3F View Figure 3 ) short, not reaching the length of two pleonites together, gradually tapering distally, with broadly rounded posterior margin.

Antennule ( Fig. 3B View Figure 3 ) eight-articled (nine-articled in MNHN.F.A51529c, Fig. 3A View Figure 3 ), fairly slender, tapering distally, 1.32 times the length of cephalothorax, with numerous aesthetascs although their distribution cannot be exactly determined owing to preservation; article 1 about 0.28 times the length of antennule, not reaching the length of articles 2 and 3 combined, about 3.96 times longer than thick, slightly expanded laterally at cephalothorax insertion, with one proximal, one medial, and one distal seta; article 2 about 0.73 times the length of article 1, 3.29 times longer than thick, with one proximal and one distal seta; article 3 about half the length of article 2 (0.56 times), about twice as long as thick (2.15 times), with three setae distally; articles 4 – 8 slightly decreasing gradually in length and thickness towards the apex, articles 4 and 5 both with one seta distally, and article 7 with two setae distally; terminal article (article 8) as long as preceding article but thinner, bearing at least three short setae apically.

Antenna ( Fig. 3D View Figure 3 ) at least five-articled (proximal area obscured), approximately half the length of antennule and much thinner; visible articles subequal in size, about 3.35 times longer than thick, without visible setae; terminal article with long setae apically, difficult to enumerate as preserved.

Mouthparts and maxilliped ( Fig. 3D View Figure 3 ) apparently reduced or lacking.

Cheliped robust; sclerite not visible; basis fairly robust, widening distally, nearly twice as long as thick (1.95 times), about 0.81 times the length of carpus, without visible setae; merus subtriangular, with up to two long setae ventrally; carpus about 2.18 times longer than thick, about 0.88 times the length of propodus, without visible setae; propodus ( Figs 2E View Figure 2 , 3E View Figure 3 ) robust, fixed finger deflexed almost perpendicular to palm, with dactylus directed medially, with one seta near the insertion of dactylus; fixed finger and dactylus unequal in length, widely separated at base forming a distinct gap between them (i.e. forcipate); fixed finger with three inner setae subdistally arising from a blunt tooth, unguis not visible; dactylus strongly developed, extending beyond fixed finger, gradually curving, with rounded end, unguis not visible.

Pereopod 1 ( Fig. 2D View Figure 2 ) much longer than following pereopods; coxa present; basis fairly slender, cylindrical, about 4.06 times longer than thick, longer than combined length of merus and carpus, with one long seta distally; ischium short; merus and carpus subequal in length, not widening distally, without visible setae; propodus longer than carpus, tapering distally, with one dorsodistal and one ventrodistal long seta; dactylus plus unguis curved and very long, about as long as propodus; unguis not distinguishable. Pereopods 2 – 3 ( Fig. 2D View Figure 2 ) as pereopod 1 but shorter; merus together with carpus about half the length (0.56 times) of the combined length of merus and carpus 1, with up to one and two distal short setae, respectively; propodus about half the length of propodus 1 (0.57 times), with one dorsodistal and one ventrodistal short seta; dactylus plus unguis about 0.39 times the length of dactylus plus unguis 1, about 0.69 times the length of propodus; unguis not distinguishable.

Pereopods 4 – 6 similar in length to pereopods 2 and 3 but sturdier; coxa present; basis fairly robust, more inflated than in pereopods 1 – 3, about 2.85 times longer than thick, longer than combined length of merus and carpus, with one long seta distally; ischium short; merus and carpus subequal in size, not widening distally, merus without visible spines and carpus with up to two minute spines; propodus longer than carpus, tapering distally, with up to two dorsodistal minute spines; dactylus plus unguis slightly shorter and stouter than in pereopods 2 – 3, claw-like; unguis not distinguishable.

Pleopods all alike; basal article rounded, without visible setae; endopod and exopod subovate, with long setae bundled together in a pointed process sticking out under the pleon.

Uropod ( Fig. 3F, G View Figure 3 ) biramous, the endopod about 9.29 times the length of exopod; basal article elongated, about 2.48 times longer than thick, longer than exopod, without visible setae; endopod greatly elongated but shorter than pleon, with six subequal articles, each article about 2.60 times longer than thick, with up to two setae distally (difficult to exactly enumerate as preserved) except for the terminal article, which ends with four long setae; exopod very short, thinner than endopod, reaching slightly beyond half the length of endopodal article 1, with two subequal articles, article 1 with one short seta distally, article 2 ending with two long setae.

Remarks

Paratype MNHN.F.A51529c of E. pyrenaensis sp. nov. has a nine-articled antennule instead of eightarticled as in the other type specimens of the species. However, this may be intraspecific variation; note that in Recent species with a large number of flagellar segments (more than five) there may be differences of one or more (an example being males of Leptochelia acrolophus Bird, 2015 , with six to ten flagellar articles depending on body size; Bird, 2015).

As mouthparts are apparently reduced or lacking in paratype MNHN.F.A51529b, the specimen should be considered a terminal male stage, devoted solely to reproduction. In fact, in mature, especially natatory, males of most tanaidomorphan genera [e.g. Cryptocopoides (Sieg, 1973 in M.S.) Sieg, 1977, Leptochelia Dana, 1849 , Leptognathia Sars, 1882 , Paratanais Dana, 1852 , Sinelobus Sieg, 1980 , and Tanaissus Stebbing, 1891 ], the mouthparts (including the maxilliped) undergo different degrees of reduction, in extreme cases rendering the animal a nonfeeding individual ( Larsen, 2005; Bła zewicz- _ Paszkowycz et al., 2014). Mouthparts cannot be examined in the specimens of E. terminator and E. seilacheri owing to fossilization position. However, it is worth noting that the alavatanaid males of Al. carabe were described as having well-developed mouthparts ( Sanchez-Garcıa et al., 2015).