High biodiversity in Polychelida crustaceans from the Jurassic La Voulte-sur-Rhône Lagerstätte

ABSTRACT The Middle Jurassic La Voulte-sur-Rhône Lagerstätte preserves with remarkable details a highly diversified bathyal palaeocommunity dominated by arthropods. Polychelida Scholtz & Richter, 1995 are particularly abundant and are currently represented by Eryon ellipticus Van Straelen, 1923, Proeryon giganteus (Van Straelen, 1923), Hellerocaris falloti (Van Straelen, 1923), and Willemoesiocaris ovalis (Van Straelen, 1923). This new investigation reveals the presence of two new genera and three new species in this crustacean community: Voulteryon parvulus n. gen., n. sp., Cycleryon romani n. sp., which is the oldest occurrence of the genus, and Adamanteryon fourneti n. gen., n. sp., an enigmatic polychelidan of uncertain affinities. The genus Proeryon Beurlen, 1928 is also revised to solve problems of homonymy, and as a consequence we here propose the replacement name Proeryon zehentbaueri pro Proeryon giganteus Beurlen, 1930, non Proeryon giganteus (Van Straelen, 1923). These new results place the La Voulte polychelidan lobster community at the first rank in terms of familial and generic diversity (three families, seven genera) and at the second rank in terms of species diversity (seven species) just after the Late Jurassic Eichstätt Lagerstätte (eight species). Thanks to modern techniques, such as X-ray tomography, this study also documents structures never observed before such as thoracic appendages of Proeryon giganteus and Hellerocaris falloti. In the case of Hellerocaris falloti, these new observations suggest it is one of the closest fossil relatives to extant polychelids.


INTRODUCTION
Polychelidan lobsters are a peculiar group of decapod crustaceans distinguished by a reduced rostrum, a dorsoventrally flattened body, and five pairs of pereiopods (walking limbs): the first pair is large and clawed; the uncertain affinities.e genus Proeryon Beurlen, 1928 is also revised to solve problems of homonymy, and as a consequence we here propose the replacement name Proeryon zehentbaueri pro Proeryon giganteus Beurlen, 1930, non Proeryon giganteus (Van Straelen, 1923).ese new results place the La Voulte polychelidan lobster community at the first rank in terms of familial and generic diversity (three families, seven genera) and at the second rank in terms of species diversity (seven species) just after the Late Jurassic Eichstätt Lagerstätte (eight species).anks to modern techniques, such as X-ray tomography, this study also documents structures never observed before such as thoracic appendages of Proeryon giganteus and Hellerocaris falloti.In the case of Hellerocaris falloti, these new observations suggest it is one of the closest fossil relatives to extant polychelids.
e focus of the present study is to propose a modern reinvestigation of the La Voulte polychelidans .We review Van Straelen's species, describe new species based upon new specimens, and assess the significance of the La Voulte polychelidan lobster diversity.
GEOLOGICAL SETTING e La Voulte Lagerstätte crops out in the Ravin des Mines (Fig. 1), about 1 kilometer west of the village of La Voulte-sur-Rhône (Ardèche Departement, France, c. 150 km south of Lyon). is outcrop is located on the eastern bank of the Rhône valley, on the southeast margin of the crystalline Hercynian basement of the Massif Central.Structurally, the Lagerstätte belongs to the sediment cover deposited on the Ardèche palaeomargin, a passive margin connecting the submerged Massif Central and the Subalpine Basin, a basin connected to the Tethys Ocean.
e geological context of the formation and evolution of the passive margin on which La Voulte-sur-Rhône Lagerstätte is defined in Elmi (1967Elmi ( , 1990) ) and detailed in Charbonnier et al. (2007a) and Charbonnier (2009).

SAMPLING
e present study is based upon 84 specimens from La Voulte listed before the description of each species.Van Straelen's type material and many historical specimens are housed at the Université Joseph Fourier, Grenoble (ex Institut Dolomieu).Other historical specimens and material collected during field expeditions are housed at the Université Claude Bernard Lyon 1 (Villeurbanne).Finally, fossils collected in La Voulte-sur-Rhône under the supervision of MNHN, Paris and CNRS during the 1983-1986excavations (for details see Fischer 2003) are housed in the MNHN collections.Finally, a few rare specimens harvested in the middle of the twentieth century or earlier are dispersed in other collections: University of Zurich (Switzerland), Staatliches Museum für Naturkunde, Stuttgart (Germany) and Université Pierre et Marie Curie (Paris 6), France.Most of studied specimens are included within nodules.Other specimens are flattened in marly beds.IMAGERY Specimens were mostly studied using a Wild Heerbrugg TYP 308700 binocular and a camera lucida.Specimens displaying low contrast were imaged either: 1) under cross-polarized light (i.e.light source equipped with a linear polarizing filter and camera lens also equipped with a polarizing filter whose optical axis is perpendicular to that of light source polarizer) to reduce reflexion and glare; or 2) under UV-light for specimens presenting a UV-yellow fluorescence.Some small specimens were imaged on a Hitachi Analytical Table Top Scanning Electron Microscope and a Jeol Neoscope 2 JCM 6000 scanning electron microscope.Photographic close ups of very small specimens were obtained by combining multiple pictures in cross-polarized light by an image stacking program (Zerene stacker, Zerene system Inc.).

X-RAY TOMOGRAPHY
Additionnaly, specimens UJF-ID.14023 and UJF-ID.11551were imaged by a tomograph v|tome|x L 240-180 (manufacturer: GE Sensing & Inspection Technologies -phoenix x|ray) equipped with a microfocus 240kV/320W tube, at the MNHN's X-ray tomography imagery platform.Data from X-ray tomograph were saved as series of 16 bits grayscale pictures representing virtual slices of the specimen, grayscale values indicating differences in absorption of x-ray within nodule.ese two specimens were then virtually reconstructed as three dimensions models (Figs 6B; 9B) using Mimics software (© Materialise).Other image stacks were directly visualized on Fiji (Schindelin et al. 2012)

TAPHONOMIC REMARKS
Observations of the nodule structure from X-ray tomography reveal undocumented features of La Voulte crustaceans.Crustaceans in nodules are preserved in volume, but more or less vertically compressed.e exoskeletons and soft parts are preserved in minerals absorbing less-X-ray than surrounding matrix, these minerals perhaps corresponds to calcite mentioned by Wilby et al. (1996).
e exoskeleton is often coated with a mineral absorbing more X-ray than surrounding matrix, this may correspond to pyrite and/or galena, both observed by Wilby et al. (1996) (see also Fig. 9E representing a specimen coated with pyrite in marly beds).e first pereiopods, the distal part of the pleon, and the telson are often lacking; they do not seem to have been encompassed by the nodule during its formation.Nodules sometimes contain one concentric layer of concretion located between the fossil and surface of nodule.One specimen of Willemoesiocaris ovalis contained within a nodule still preserves parts of its digestive track.However, these sections of digestive track are discontinuous.For these reasons, it seems that the nodules have formed early after the death of the crustacean, after the decay has already begun, but before it led to disarticulation.e nodule growth started near the middle of the specimens, and for some reasons often stopped before encompassing the whole body.Finally, the nodules have been deformed by compaction of surrounding rocks during diagenesis.It is interesting to note that specimens preserved in marly beds seem quite similar in term of fossilization to specimens in nodules, except they are usually more flattened.
-Widened and rounded carapace not confluent in outline with pleon; uropodal exopod without diaeresis; deep cervical and postcervical incisions (except in Knebelia).

REMARKS
Eryonidae is probably the best-known family of fossil polychelidan lobsters.Initially, this family used to encompass all polychelidans, but, with the discovery of new species, new families were erected to better describe polychelidan diversity.Eryonidae includes genera characterized by a widened and rounded carapace not confluent in outline with the pleon and an absence of the diaeresis.Moreover, most Eryonidae, except Knebelia are characterized by deep cervical and postcervical incisions.Recently Wrangleryon perates Feldmann, Schweitzer & Haggart, 2013 was described as an eryonid due to "distinct terga with keeled and subtriangular pleura, subtriangular telson".First of all, the importance of this discovery should be stressed; it is the single known North American polychelidan (examination of type material of Palaeopentacheles? starri Schweitzer & Feldmann, 2001 from the early Oligocene of the State of Washington, USA, reveals that it is not a polychelidan but probably a nephropoid lobster, and the structure interpreted as a pectinate claw is the pair of third maxillipeds).Despite the poor state of preservation of the unique specimen of Wrangleryon, it will be noted that pleura are indeed subtriangular, but do not appear to be keeled.Subtriangular pleura, distinct terga and triangular telson are all rather widespread within polychelidan and can be found in the diverse Coleiidae Van Straelen, 1925and Polychelidae Wood-Mason, 1874. Wran-GEODIVERSITAS • 2014 • 36 (4) gleryon carapace is not preserved.However, alignment of pereiopods, suggests they probably rested against the lateral margin of carapace.e shape of carapace can therefore be roughly observed: it was with little doubt ovoid and not much wider than the pleon, characters incompatible with an ascription to Eryonidae.Finally, the absence of diaeresis observed on Wrangleryon is truly difficult to assess: exopodal uropods are poorly preserved: the one on the right side of specimen is broken distally; the one on the left side possibly possess a structure reminiscent of a diaeresis but by far too poorly preserved to assess its nature.It must, nevertheless be noted that absence of diaeresis is not unique to eryonids, as it also occurs in polychelids and palaeopentachelids.It seems therefore reasonable to exclude this genus from Eryonidae.However, the question remains open on its place within polychelidans.New, well-preserved specimens may give more clues on the exact affinities of Wrangleryon.

REMARKS
Eryon Desmarest, 1817 is the first described genus of polychelidan lobsters.As such, it was used as a catch-all name to accommodate most fossil species of polychelidan lobsters.Although a second polychelidan genus -Coleia Broderip, 1835 -was described, Woodward (1866Woodward ( , 1881Woodward ( , 1911) ) overlooked the diversity of polychelidan lobsters and ascribed all known species to Eryon.

Pleon
Pleon half wide as carapace; s1 tergum shorter than the others; subrectangular s2-s5 terga bearing two transverse grooves converging medially, and an axial carina stretching from behind anterior transverse groove, cutting the posterior one and reaching posterior margin; subtriangular s2-s3 tergopleura (part of terga folded laterally), with a small axial process at the fold separating tergopleura from terga; s4-s5 poorly preserved.

Eyes and cephalic appendages
Small pear shaped eyes carried on a rather long peduncle and projected from a tubular protrusion; antennula composed of a few proximal oblong podomeres carrying a flagellum of not assessable length, probably rather long (second flagellum not preserved); antenna composed of an antennal pe-  duncle with three segments (short subtrapezoidal ischiocerite, subcylindrical merocerite, subtriangular carpocerite with enlarged distal margin) and multiarticulated flagellum of not assessable length attached to carpocerite; scaphocerite not preserved or absent.
oracic appendages Chelate, long and slender first pereiopod, with a propodus about as long as carapace.
Ornamentation Dorsal surface of exoskeleton covered by a few very small tubercles scattered on the surface.

REMARKS
Eryon ellipticus has always been ascribed to Eryon.However, since Eryon used to accommodate all fossil species of polychelidan lobsters, we justify herein the generic assignation of E. ellipticus. is species is ascribed to Eryon based upon its tubular protrusion of the anterolateral angle housing the eye peduncle, its large anterolateral cervical spine separating the anterolateral margin from the cervical incision, its mediolateral margin reduced to a very large spine and its well-marked branchial and postcervical carinae.All characters are similar to Eryon cuvieri, type species of Eryon.e scaphocerite appears to be missing.Although it is impossible to rule out that it was not preserved, it could be noted that scaphocerite is apparently also lacking in E. cuvieri.Eryon ellipticus can be distinguished from E. cuvieri by its marked cervical and postcervical grooves (very shallow in E. cuvieri), its longer ocular peduncle housed in a longer tubular protrusion, its larger visual surface, and its postcervical incisions which are wider toward the edge of the carapace (narrower in E. cuvieri) at the opening of the incision.Eryon ellipticus resembles E. sublevis by its marked cervical and postcervical grooves, but can easily be distinguished from this species by a wider frontal margin, more oblique tubular protrusion (oriented more anteriorly in E. sublevis) and smaller posterolateral spines.e holotype of E. sublevis is too incomplete to allow further comparisons.Eryon ellipticus is the stratigraphically oldest known occurrence of the genus in the fossil record.
EMENDED DIAGNOSIS.-Dorsoventrally flattened carapace with a subcircular outline in dorsal view, subcircular ocular incision, strengthened by orbital carina, deep cervical and postcervical incisions, postcervical incision deeper than cervical incision, straight or slightly convex anterolateral and mediolateral margins, carapace outline not confluent with that of pleon, uropodal exopod without diaeresis.

REMARKS
Eryon and Cycleryon share numerous characteristics: a large carapace with deep cervical and postcervical incisions, very shallow cervical and postcervical grooves and an absence of diaeresis on the uropodal exopod.For these reasons, species of these genera were mixed for a long time.For instance, Knebel (1907) classified all species now ascribed to Eryon and Cycleryon, and Knebelia schuberti to Eryon, within a group called "Eryonidae latiformes" (i.e.wide eryonid).e first attempt to discriminate these "wide eryonids" was made by Glaessner (1929), who ascribed E. elongatus, E. orbiculatus, E. spinimanus and E. propinquus to Coleia Broderip, 1835 probably based upon the general shape of the carapace.2014 • 36 (4) Finally, Beurlen & Glaessner (1930) erected Cyclocaris to accommodate the species listed above.However, since Cyclocaris was preoccupied, Glaessner (1965) proposed the replacement name Cycleryon.

GEODIVERSITAS •
According to Glaessner (1965), Eryon and Cycleryon are clearly distinguished by the ocular incision separated from anterolateral angle (tubular protrusion in Eryon) and the straight mediolateral margin (reduced to a large spine in Eryon).

Carapace carinae and grooves
Postrostral and postcervical carinae raised, marked by a row of tubercles on each side, not separated by cervical groove; short and raised postrostral carina extending on the posterior half of cephalic region, anteriorly connected to a large area with a coarse tubercle ornamentation widening anteriorly, marked by a row of tubercles on each side; raised postcervical carina, connected to postrostral carina and ornamented by a row of tubercles decreasing in size posteriorly on each side; branchial carina cut by cervical groove, curving inward anteriorly, slightly sinuous posterior to postcervical groove, slightly raised and marked by a row of tubercles; posterior margin strengthened by carina, cut by postcervical carina, raised and marked by a row of large tubercles; very shallow cervical groove extending from cervical incision to reach median line without cutting it; shallow postcervical groove extending from postcervical incision to reach branchial carina, cut by branchial carina, oblique between branchial and postcervical carinae, curving forward before reaching without cutting postcervical carina; short gastroorbital groove, extending anteriorly from cervical groove between postorbital and postrostral carinae.

Pleon
Pleon half as wide as carapace; subrectangular, smooth s1 tergum shorter than the others; subrectangular s2-s3 terga, with a pair of transverse grooves converging medially and a short median carina, with an anterior spine, cutting posterior transverse groove; subrectangular s4-s5 terga, with a pair of transverse grooves converging medially and a short median carina cutting posterior transverse groove; Audo D. et al. elongate s1 tergopleuron, with a small axial process at the fold separating tergopleuron from tergum; s2 tergopleuron poorly preserved, with small axial process at the fold separating tergopleuron from tergum; s3-s4 tergopleura hooked, with small axial process at the fold separating tergopleura from terga.

Eyes and cephalic appendages
Small eye, entirely contained within ocular incision; antennula with wide basipodite carrying long and slender outer flagellum (exopodite) and endopodite consisting of at least two enlarged podomeres carrying a large flagellum of inaccessible length (at least as long as antennal peduncle); antenna composed of wide subtriangular basipodite, carrying slender fusiform scaphocerite (exopodite) and endopodite with subtriangular first podomere, cylindrical second podomere and distal part forming small flagellum.
oracic appendages Chelate, large and elongate first pereiopod, with a propodus about as long as carapace and a stout, subtriangular carpus; poorly preserved, short, achelate fifth pereiopod.

Ornamentation
Carapace with coarse and dense cover of tubercles on the cephalic region anterior to postrostral carina, thinner and scattered on the rest of the carapace, almost lacking between branchial carinae.

REMARKS
Cycleryon romani n. sp. is ascribed to Eryonidae based upon the wide, dorsoventrally flattened, carapace not confluent in outline with that of the pleon and axial carina on pleonal terga cutting posterior transverse groove.It is ascribed to Cycleryon based upon of the subcircular carapace, the carinate ocular incision, the deep cervical and postcervical incisions (postcervical incision deeper), the slightly convex anterolateral margin, and the straight mediolateral margin.Cycleryon romani n. sp.differs from all other species of Cycleryon by its deeper, subrectangular cervical and postcervical incisions.In addition, a very small specimen MNHN.F.A50728 (Fig. 4F) possessing a similar shape of carapace and a short P1 propodus is tentatively ascribed to Cycleryon romani n. sp.

DISCUSSION
All studied specimens referred to Voulteryon n. gen.are probably juveniles; a possible adult specimen is figured by Charbonnier (2009: fig. 404) as a Willemoesiocaris ovalis, but is not accessible to scientific enquiry.Voulteryon n. gen. is ascribed to Eryonidae on the basis of the deep cervical and postcervical incisions (as in Eryon, Cycleryon, Soleryon, Rosenfeldia and Tethyseryon), the cervical groove not cutting median line (as in Eryon, Cycleryon, and possibly in Soleryon), and the axial carina cutting posterior transverse groove on s2 to s5 terga (as in Eryon, Cycleryon, Knebelia, Soleryon, and Rosenfeldia).Carapace is also not confluent in outline with pleon, a character shared in all Eryonidae.However, this character is also documented for many juvenile polychelidan specimens such as those of Palaeopentacheles (Audo et al. 2014b: fig.6D) and in extant eryoneicus larvae (Bernard 1953;Martin 2014).It may correspond to the retention of an ancestral juvenile character in Eryonidae and therefore cannot be taken into account.Voulteryon n. gen.differs from Eryon, Cycleryon, Soleryon and Rosenfeldia in having a shallow ocular incision (deep in all aforementioned genera) and narrower carapace (broad in all aforementioned genera), from Knebelia by its deeper cervical and postcervical incisions (shallow in Knebelia), unsegmented frontal margin (with frontal lobes in Knebelia), from Tethyseryon in having an axial carina cutting posterior transverse groove on s2 to s5 (carina cut by posterior transverse groove in Tethyseryon) and its narrower carapace (broader in Tethyseryon).E). -Paratype: MNHN.F.A29151 (Fig. 5F).

Pleon and telson
Pleon about as long as carapace, about half as wide as carapace; short s1 tergum, badly preserved; s2-s5 with subrectangular terga bearing two transverse grooves converging medially, and axial carina, marked by a pair of rows of tubercles, stretching from behind anterior transverse groove, cutting the posterior one and reaching posterior margin; s2-s5 with lanceolate tergopleura.

Eyes and cephalic appendages
Large spherical eyes, slightly projected from ocular incision; cephalic appendages poorly preserved.
oracic appendages Large first pereiopod with a short carpus and a long propodus, poorly preserved.-Pleonal appendages: only poorly preserved uropods.

REMARKS
Coleiidae is a large family, mostly due its type genus Coleia, to which twenty species are currently ascribed (Schweitzer et al. 2010).A quick examination of Coleia shows it is probably a waste-basket genus since it includes species varying greatly in morphology.
However, the problems with coleiids are not confined to Coleia.Indeed, Van Straelen (1925) defined rather loosely the family as polychelidans with a diaeresis on the uropodal exopod, ocular incisions and always a scaphocerite.is definition is quite problematic: 1) ocular incisions are shared by all extant and fossil polychelidans (except in Eryon, in which the incision is modified in tubular protrusion); 2) the scaphocerite is probably only missing in Eryon; and (3) the presence of a diaeresis occurs in multiple decapod crustaceans (dendrobranchiate shrimps, carideans, and many groups of reptantians), this character distribution is therefore difficult to assess, and it could, in fact, be plesiomorphic for polychelidan lobsters.Ahyong (2009) proposed the first phylogenetic analysis including fossil and extant polychelidans.Unfortunately, for the Coleiidae, Ahyong (2009) did not consider Coleia antiqua (type species of Coleia, type genus of the family) but based his analysis upon Palaeopolycheles longipes (Fraas, 1855), which was then considered to be a member of Coleia (Schweigert & Dietl 1999).He provided a new definition of Coleiidae based on the following characters: U-shaped ocular incision, well-developed eye directed laterally, postorbital carina aligned with branchial carina, cervical and postcervical grooves marked across carapace, shallow cervical and postcervical incisions, and second and third pleonites tergopleura identical (i.e.s2 tergopleuron not saddle-shaped).
However, it shall be noted that: 1) U-shaped ocular incisions occur also in Palaeopentacheles roettenbacheri (Münster, 1839)  For these reasons, it is still difficult to precisely define Coleiidae.We propose herein to include within Coleiidae polychelidan lobsters with 1) a sharp anterolateral angle forming the anterior margin; 2) a widely open (i.e.hemicircular to "U-shaped") ocular incision; 3) a well-developed eye; 4) a well-marked cervical groove curving backward near median line; 5) uropodal exopod with a curved diaeresis; and 6) a third maxilliped with enlarged ischium. is definition is temporary.Indeed, these characters may reveal plesiomorphic or even non-informative, but they seem to be quite representative of Coleiidae, including Coleia antiqua, in its modern conception (Schweitzer et al. 2010).Only a new phylogenetic analysis including a large number of coleiids may allow defining properly this family.
DIAGNOSIS.-Dorsoventrally flattened carapace; large, slightly concave anterior margin; wide hemicircular ocular incisions; rounded posterolateral angle, extending along pleon; cervical groove curving backward near median line; cervical and postcervical grooves almost parallel between lateral margin and branchial carina; posterior transverse groove on pleonal tergites cutting median line; uropodal exopod with very curved diaeresis.Knebel (1907) was the first to attempt to divide polychelidan fossils into two groups: "Eryonidae latiformes" (with a wide carapace) and "Eryonidae augustiformes" (with a narrow carapace).is work was based only on Late Jurassic polychelidan lobsters from Germany and did not take into account Early Jurassic species.Based upon Toarcian species, Beurlen (1928) considered Knebel's divisions to be artificial and proposed Proeryon, which he thought to be ancestor of "Late Jurassic species" -probably referring to Eryonidae sensu stricto.Moreover, he considered Coleia Broderip, 1835 to be more primitive.Shortly, Beurlen (1928) considered a Proeryon-group lacking a diaeresis on the uropodal exopod and a Coleia-group with a diaeresis being present.

REMARKS
Contrary to Beurlen (1928), we pointed out that Proeryon hartmanni (type species) and all the species herein included in Proeryon do possess a diaeresis on the uropodal exopod.
Proeryon also possesses a sharp anterolateral angle forming anterior margin of ocular incision, a hemicircular ocular incision, a well-developed eye projecting from ocular incision, and a third maxilliped with wide ischium; all these characters being similar to Coleia antiqua.For these reasons and according to Glaessner (1969), we maintain Proeryon in Coleiidae.However, a complete revision of this family will be required to affirm or infirm this assignment.

Carapace outline
Dorsoventrally flattened carapace, with pyriform outline in dorsal view, wider than long; slightly concave frontal margin; anterolateral angle forming a large spine; lateral margin incised by ocular, cervical and postcervical incisions; large and hemicircular ocular incision; slightly rounded anterolateral margin with a few small spines, oblique compared to longitudinal axis; anterolateral cervical spine as large as the other anterolateral spines; small, triangular, narrow cervical incision; straight mediolateral margin, longer than anterolateral margin, with a few small spines; small, triangular postcervical incision, smaller than cervical one; rounded posterolateral margin, fringed with small spines; rounded posterolateral angle, extending along pleon; wide, only slightly concave posterior margin.

Carapace carinae and grooves
Postrostral and postcervical carinae separated by cervical groove; postrostral carina raised on the posterior half of cervical region, ornamented by a single row of large tubercles; postcervical carina raised and ornamented by a single row of tubercles, cut by postcervical groove; raised postorbital carina, extending onto the anterior half of cephalic region, parallel and separated from the anterior portion of branchial carina; straight and long branchial carina, cut by cervical and postcervical grooves, raised and ornamented by tubercles; longitudinal lateral carina; deep and oblique cervical groove, stretching from cervical incision, cutting branchial carina, curving backward near median line, cutting median line and separating postrostral and postcervical carinae around half of the carapace length; deep postcervical groove, transverse between postcervical incision and branchial carina, shallow, curving backward and then forward between branchial and postcervical carinae, cutting postcervical carina; shallow branchiocardiac groove extending from the postcervical groove, on the inner side of branchial carina, curving toward median line; short gastroorbital groove, extending obliquely from cervical groove toward postrostral carina.

Pleon and telson
Pleon half as wide and slightly longer (telson excluded) than carapace; subrectangular s1 tergum shorter than others, with a pair of transverse grooves converging medially; subrectangular s2-s5 terga, with two transverse grooves, anterior one deeper and separated from anterior margin by a slightly inflated region, large median tubercle between both grooves and smaller one after posterior transverse groove; subtrapezoidal s6 tergum, with two transverse grooves, anterior one deeper and separated from anterior margin by a slightly inflated region, large median tubercle between both grooves; subtriangular and elongate s1 tergopleuron with a small axial process at the fold separating tergopleuron from tergum; subtriangular s2-s3 tergopleura with a spine curving forward in the middle of lateral margin, with a small axial process at the fold separating tergopleura from terga; s4-s6 tergopleura poorly preserved, with a small axial process at the fold separating tergopleura from terga; subtriangular telson, strengthened by two longitudinal carinae, with bulged anterior median region and a short median distal groove.

Eyes and cephalic appendages
Large eye, slightly projected from of ocular incision; antennula poorly preserved, with a long flagellum of unassessable length; antenna composed of a triangular basipodite carrying: 1) a wide, ovoid and flattened scaphocerite with a spiny distal margin, and ornamented by a few fine tubercles; and 2) an  endopodite composed of two large articles, each forming a leaf-like inner expansion and carrying a long flagellum at least as long as ⅔ of carapace; mandibles with long subtriangular apodemes, and a hemicircular thicker mesial part forming a few triangular teeth of uneven sizes.

Pleonal appendages
Slender and falciform petasma (first pleopod modified into a male copulatory appendage); uropod composed of a subrectangular basipodite carrying: 1) large exopod with rounded distal margin, lateral and longitudinal carinae and very curved diaeresis between those carinae, at about three quarters of exopod length; and 2) large endopod, with rounded distal margin and wide median carina distally effaced.

Ornamentation
Densely and finely tuberculate exoskeleton.Van Straelen, 1923 has been subject of debates linked to the fact that when the species was described, most species were still ascribed to a single genus, Eryon, following the works by Oppel (1862), Woodward (1866Woodward ( , 1881Woodward ( , 1911) ) and Knebel (1907).Besides, the figure proposed by Van Straelen (1923) is misleading because it seems to be based upon composite material.Van Stralen's reconstruction shows subcircular ocular incisions typical of Cycleryon, but unknown in Coleia or Proeryon.Van Straelen (1925) subsequently ascribed the species to Coleia due to the presence of a diaeresis and was followed by numerous successive authors such as Roman (1928), Glaessner (1929), Charbonnier (2009) and Charbonnier et al. (2010).However, Pinna (1968) placed the species in Cyclocaris then renamed Cycleryon by Glaessner (1965). is position, mainly due to Van Straelen's figure and to the subcircular shape of the carapace, was followed by Fischer ( 2003) and Garassino & Schweigert (2006).Finally, Schweitzer et al. (2010) proposed the new assignment to Proeryon but without any justifications.

Systematic position Systematic position of Eryon giganteus
We concur with the assignment to Proeryon. is assignment is based upon the wide hemicircular ocular incision, the small cervical and postcervical incisions, the cervical groove curving backward near median line, the pleonal terga with posterior transverse groove cutting axial carina, and the uropodal exopod with strongly curved diaeresis.All these characters are diagnostic of Proeryon.Proeryon giganteus differs from other species of Proeryon in having very long and slender first pereiopods (stouter in all other species), a wider carapace, and a lateral carina on branchial region.Schweitzer et al. (2010) synonymized Proeryon laticaudatus Beurlen, 1928with P. giganteus Beurlen, 1930 without any justification.Examination of the types specimens of P. giganteus (holotype by monotypy, coll.Hauff) and of Proeryon laticaudatus (two syntypes, coll.Hauff) lead us to a different conclusion.Proyeron giganteus Beurlen, 1930 shows a pyriform carapace, a broad pleon and a short anterolateral angle while in P. laticaudatus, the carapace is ovoid, the pleon is narrower and the anterolateral angle is elongate.For these reasons, we consider P. giganteus and P. laticaudatus as separate species.Consequently, this situation leads to a case of secondary homonymy.To solve this problem and according to ICZN (1999: articles 53.3, 57.3), we propose herein the replacement name P. zehentbaueri pro P. giganteus Beurlen, 1930non P. giganteus (Van Straelen, 1923).e specific epithet zehentbaueri is in honour of Michael Zehentbauer (Kösching, Bavaria, Germany), who donated important decapod crustacean material to the SNMS collection.

ONTOGENY
ree small specimens (MNHN.F.A50710, A50727, A50730, carapace length c. 9 mm) possibly represent juveniles of P. giganteus based upon their large eyes in hemicircular ocular incision.e presence of a diaer-esis on the uropodal exopod of MNHN.F.A50727 reinforces this hypothesis.Small specimens differ from larger ones by a slightly narrower carapace, and a narrower pleon.Two larger specimens (MNHN.F.A50720 and FSL 170521) are far more similar to the adults.

Carapace outline
Dorsoventrally flattened carapace with ovoid outline in dorsal view; concave frontal margin, poorly preserved; anterolateral angle forming a large spine; lateral margin incised by ocular, cervical and postcervical incisions; very large and hemicircular ocular incision opening laterally; anterolateral margin rounded posteriorly, subparallel to longitudinal axis; anterolateral cervical spine absent; large triangular cervical incision; sharp subtriangular mediolateral margin, slightly rounded posteriorly, shorter than anterolateral margin; triangular postcervical incision, smaller than cervical incision; posterolateral margin rounded anteriorly, straight posteriorly; rounded posterolateral angle confluent with pleon; slightly concave posterior margin strengthened by a posterior carina.

Carapace carinae and grooves
Postrostral and postcervical carinae absent, median line only marked by a very shallow groove; postorbital and branchial carinae merged, forming a raised carina extending from ocular incision cut by cervical and postcervical grooves then straight and reaching posterolateral angle; submarginal carina not preserved anteriorly, parallel to lateral margin, reaching posterolateral angle; deep and slightly oblique cervical groove extending from cervical incision, slightly curving backward before cutting median line at half carapace length; deep postcervical groove, transverse from postcervical incision to branchial carina, strongly curving backward near median line, reaching median line without cutting it at two thirds of the length of carapace; branchiocardiac groove extending from postcervical groove, on the inner side of branchial carina, extending backward obliquely toward median line; short gastro-orbital groove, extending obliquely from cervical groove toward postrostral carinae.

Eyes and cephalic appendages
Very large eye carried on a short peduncle; poorly preserved antennula with bulbous basipodite carrying long flagellum (exopodite) endopodite not preserved; antenna formed of long and slightly curved basipodite inserted near ocular peduncle, carrying: 1) pyriform scaphocerite (exopodite) strengthened by longitudinal median carina; and 2) endopodite consisting of two subrectangular podomeres carrying thin flagellum of unassessable length (probably short); mandibles with subtriangular apodeme, incisor process forming teeth of uneven size (one bigger than the others) and short poorly preserved palp (consisting at least of two podomeres) articulated anteriorly at the boundary between apodeme and incisor process.oracic appendages Mx3 with large subtriangular ischium carrying four subrectangular podomeres decreasing in size distally; extremely elongate, slender, chelate P1, with ischium cut by autotomy zone, elongate and thin merus with bulbous anterior portion, elongated, thin carpus, propodus forming a long palm and a long pollex, long and thin dactylus; chelate, very thin and elongate P2-P4.

Pleonal appendages
Uropods with ovoid endopod strengthened by raised median carina and petaloid exopod strengthened by raised median carina and faint lateral carina along its lateral margin, cut by rounded diaeresis.

Ornamentation
Carapace and pleon covered by tubercles.
ey share the typical shape of adult claws and differ mainly in their larger eyes, narrower pleon and rounder carapace (Fig. 8D).

REMARKS
Polychelidae is the only family of extant polychelidan lobsters including only blind species, with their cornea and sometimes even the ocular peduncle reduced (Galil 2000).Four fossil genera have been ascribed to Polychelidae (Glaessner 1969): Antarcticheles Aguirre-Urreta, Buatois, Chernoglasov & Medina, 1990, Pal-aeopolycheles Knebel, 1907, Palaeopentacheles Knebel, 1907, and Willemoesiocaris Van Straelen, 1925.Willemoesiocaris and Palaeopolycheles are herein provisionally assigned to Coleiidae.Palaeopentacheles is currently ascribed to its own family Palaeopentachelidae by Ahyong (2009).Antarcticheles is included in Polychelidae by Aguirre-Urreta et al. (1990) based upon the shape of carapace, distinct cervical and postcervical grooves and median carina.Examination of high resolution pictures of the holotype of Antarcticheles antarcticus Aguirre-Urreta, Buatois, Chernoglasov & Medina, 1990 reveals large rounded ocular incisions that probably housed well-developed eyes.Direct comparison with the V-shaped to slit-like or reduced ocular incisions in extant polychelid species, suggests that Antarcticheles is not a true member of Polychelidae but more probably a member of the stem-group of Polychelidae.In conclusion, we consider that Polychelidae do not include fossil representatives and that the family should be restricted to species sharing the principal synapomorphy distinguishing polychelids from all fossil polychelidans: the reduction of the eyes.It could be noted that this synapomorphy is only, of course, only relevant within polychelidans: blind species also occurs in other clades of reptantians (for instance Acanthacaris Spence-Bate, 1888, Thymops Holthuis, 1974 andThymopsis Holthuis, 1974;-see Holthuis 1974).

REMARKS
Hellerocaris falloti was initially ascribed to Palaeopolycheles by Van Straelen (1923). Later, Van Straelen (1925) erected a new genus to accommodate this species but without justification.Directly comparison based upon the type specimens reveals that Hellerocaris differs from Palaeopolycheles based upon its subrectangular carapace (ovoid in Palaeopolycheles), its smaller ocular incisions, its shallow cervical and postcervical incisions (deeper in Palaeopolycheles), its axial carina on pleonal terga cutting posterior transverse groove (cut by posterior transverse groove in Palaeopolycheles), its fusiform scaphocerite (subcircular in Palaeopolycheles), and its small diaeresis cutting the distal extremity of uropodal exopod (wider in Palaeopolycheles).
Hellerocaris was one of the two genera initially ascribed to Coleiidae by Van Straelen, (1925) based upon the presence of a diaeresis on uropodal exopod, ocular incisions and a scaphocerite.is position was followed by all successive authors.Examination of the type material of H. falloti and of new specimens leads us to a different conclusion.Indeed, the cervical and postcervical incisions in Hellerocaris are very small (Figs 2J; 9A, C, D, G; large in Coleia), the Mx3 ischium is slender (widened in Coleia, Proeryon), the s2 tergopleuron is saddle-shaped (triangular in all coleiids) and overlaps the s1 tergopleuron (no overlap in all coleiids).us, we consider Hellerocaris to be not a true member of Coleiidae.Instead, we assume that Hellerocaris exhibits more affinities with the Polychelidae (e. g. narrow carapace, shallow cervical and postcervical incisions, axial carina cutting transverse groove on s2-s5, s2 tergopleura overlapping s1 tergopleura) but without sharing all the diagnostic characters of the Polychelidae such as the reduced eyes and the eryoneicus larvae: Indeed, the occurrence of very small specimens (Fig. 9G) is probably incompatible with that of giant eryoneicus larvae which are usually far larger than these specimens.Moreover, Hellerocaris shows well-developed eyes and adult-like juveniles.For these reasons, as for Antarcticheles, we consider Hellerocaris to be a member of the stem-group of Polychelidae.(Van Straelen, 1923) (Figs 2J-L; 9)

Carapace carinae and grooves
Postrostral and postcervical carinae separated by cervical groove; postrostral carina raised in the second half of cephalic region; raised postcervical carina; postorbital and branchial carinae merged, forming a raised carina extending from ocular incision cut by cervical groove then parallel to median line and reaching posterolateral angle; thin submarginal carina stretching from ventral margin anteriorly near Mx3 insertion, parallel to lateral margin, reaching posterolateral angle; deep and slightly oblique cervical groove extending from cervical incision, slightly curving backward before cutting median line at half the carapace length; postcervical groove very deep from postcervical incision to branchial margin, effaced near branchial margin, curving backward then forward between branchial carina and postcervical carina; faint branchiocardiac groove extending obliquely from postcervical groove near branchial carina to posterior portion of postcervical carina; short gastro-orbital groove extending longitudinally from cervical groove where it bends posteriorly (between branchial and postrostral carinae); deep inferior groove (on ventral side) connected to postcervical groove through postcervical incision, cutting pterygostomian flap transversally, cut by submarginal carina; shallow hepatic groove (on ventral side) extending longitudinally from the antennal groove to inferior groove; deep antennal groove extending longitudinally from ocular incision, curving outward to merge with cervical groove through cervical incision.

Eyes and cephalic appendages
Small eye slightly projected from ocular incision; poorly preserved antennula, consisting of wide basipodite carrying two flagella, inner one (endopodite) being thicker than the outer (exopodite); poorly preserved antenna, endopodite composed of three subcylindrical podomeres carrying a flagellum of unassessable length, narrow, fusiform scaphocerite (exopodite), with a sharp tip; mandibles with a long subtriangular apodeme carrying incisor process forming sharp teeth of uneven size.

oracic appendages
Elongate Mx3 inserted very close to P1, with slender ischium and merus, stocky carpus, propodus and small dactylus; large, chelate P1; slender P1 ischium cut by an autotomy zone, and slightly too short to reach the carapace margin; P1 merus slightly longer than ischium and widening distally, short subtriangular P1 carpus; elongate P1 propodus, about three times as long as carpus; slender P1 dactylus about one third of the length of propodus; chelate P2-P4, smaller than P1, composed of subcylindrical podomeres of similar width; P5 slightly shorter than P2-P4, distal extremity too poorly preserved to check presence of a claw.

Pleonal appendages
Pleopods poorly preserved; uropods with: subquadrate basipodite; long uropoal exopod with a small diaeresis at the distal extremity, a straight outer margin, a curved inner margin fringed by dense setae, a pair of shallow longitudinal grooves surrounding a slightly vaulted area; lanceolate uropodal endopod, fringed by setae on its inner margin and strengthened by a raised carina surrounded by shallow grooves.

Ornamentation
Carapace and pleon covered by small tubercles.

ONTOGENY
Six specimens (MNHN.F.A29520, A48872, A48873, A50709, A50732, A50733) have a carapace length ranging from c. 4 to 7 mm (e.g., Fig. 9G).ey are far smaller than other specimens whose carapace lengths measure c.21 mm.ese specimens slightly differ from larger specimens by slightly more convex lateral margin and proportionally larger eyes.We interpret these specimens as juveniles of H. falloti.

REMARKS
Adamanteryon n. gen.clearly differs from all other polychelidan lobsters by its unique diamond-shaped carapace outline.Its familial assignment is however uncertain due to the poor preservation of the single available specimen of this monospecific genus.
e length of antennules and antennae, and the posterolateral angle of carapace apparently closely associated with pleon point toward an assignment to Coleiidae.Alternatively, the wide carapace corresponds more closely to the Eryonidae habitus.Additional, more well-preserved samples will therefore be required to shed light on the familial affinities of this unusual genus.

Carapace outline
Dorsoventrally flattened carapace with a diamondshaped outline in dorsal view; concave frontal margin, narrow compared to width of carapace; anterolateral angle forming a large spine; ocular incision poorly preserved; cervical and postcervical incisions absent or very small; angular posterolateral angle, not associated with pleon; wide and concave posterior margin, poorly preserved.

Pleon
Poorly preserved pleon, less than half the width of carapace and probably about as long as carapace.

Eyes and cephalic appendages
Antennula composed of a wide basipodite carrying a long and slender outer flagellum (exopodite) and an endopodite consisting of at least two enlarged podomeres carrying a long flagellum of unassessable length; antenna with a very long and thin flagellum, probably longer than carapace, scaphocerite not preserved.

HIGH DIVERSITY OF POLYCHELIDAN LOBSTERS
e fossil record of polychelidan lobster is almost entirely documented by specimens from Lagerstätten.As a result, the record is rather discontinuous and study of variations in palaeobiodiversity would be strongly biased by the relative abundance of Lagerstätten.For instance, the occurrence of very extensive "Solnhofen-type" Lagerstätten in the Late Jurassic of Europe leads to a high known palaeobiodiversity in this period.In the Middle Jurassic, only two Lagerstätten have yielded polychelidan lobsters: Monte Fallano (one species, Bravi et al. 2014) and La Voulte (seven species, present study).For this reason, the La Voulte Lagerstätte fills an important gap in the fossil record of polychelidan lobsters.
is high diversity of La Voulte polychelidans is evident when compared to other Lagerstätten (Fig. 11).Comparison of specific, generic, and familial diversity of eight Jurassic Lagerstätten yielding multiple species of polychelidan lobsters highlights that the La Voulte Lagerstätte is the second outcrop in term of specific diversity and the first in term of generic and familial diversity.Surprisingly, the very small La Voulte outcrop (about 200 m²) can be compared in term of palaeobiodiversity to well-known, extensively quarried Lagerstätten such as Lyme Regis or Eichstätt basin.One of the most striking differences between La Voulte and other Lagerstätten is that each species at La Voulte belongs to a separate genus: there is great phylogenetic diversity in addition to specific diversity.is contrasts with 1) the Osteno Lagerstätte where all species are ascribed to Coleia (Pinna 1968, 1969, Teruzzi 1990); 2) the Eichstätt Lagerstätte where three species of Cycleryon and two of Knebelia are described (Frickinger 1994, 1999, Audo et al. 2014b); and 3) the Holzmaden Lagerstätte where four species or five are ascribed to Proeryon (Beurlen 1928(Beurlen , 1930(Beurlen , 1944;;Hauff & Hauff 1981).A more comparable situation is found in Nusplingen, where the generic diversity is almost equal to the specific diversity (Dietl & Schweigert 2001, 2004, 2011;Schweigert 1997;Schweigert et al. 2012).However, Nusplingen has not yielded yet as many species as La Voulte.
e origin of La Voulte polychelidan high palaeobiodiversity remains to be understood.However, it suggests that either polychelidans are primarily deep-sea crustaceans, or that rather early in their evolution, at least three polychelidan lobster families (Eryonidae, Coleiidae, "stem-Polychelidae") had already colonized deep-water palaeoenvironments.

ORIGIN OF POLYCHELIDAE
Extant polychelids inhabit deep-water environments (Galil 2000).It could be expected that their closest fossil relatives may also have lived in rather deep environment, such as La Voulte.e reinvestigation of Hellerocaris suggests it might be a close relative of Polychelidae.In addition to the developed eye (and supposed absence of eryoneicus larva), Hellerocaris also differs from Polychelidae by a small diaeresis at the distal extremity of uropodal exopod.is diaeresis is very small compared to that of other polychelidan lobsters.is observation suggests that the loss of the diaeresis in Polychelidae may have occurred by a gradual displacement toward the distal extremity of the diaeresis until it was finally lost. is scenario is also compatible with the stratigraphic record: the earliest polychelidan species (Triassic), Tetrachela raiblana Bronn, 1858, possesses a large diaeresis; H. falloti indeed is dated into the Middle Jurassic; earliest species of polychelidan, Tetrachela raiblana Bronn, 1858, possesses a large diaeresis; and polychelids are extant.
Extant polychelids develop indirectly through an eryoneicus larva. is larva is of large size and characterized by an inflated, balloon-like carapace ornamented by abundant spines and possesses reduction of eyes, as in extant adult polychelids (Bernard 1953;Martin 2014).e fossil record of polychelidan lobsters is mainly known from specimens of large size, and rare juveniles similar to the adults (Bravi et al. 2014;Audo et al. 2014b).
e only known true larvae of polychelidan lobster have been identified but not yet published from the Hadjoula Lagerstätte (Late Cretaceous, Lebanon) and resemble eryoneicus larvae by their large size and spinose carapace and differ from them by their developed eyes and uninflated carapace.
As mentioned in the systematic treatment, H. falloti and W. ovalis are probably among close relatives of extant polychelids.Small specimens of both species have been identified in La Voulte (Figs 8D; 9G).eir morphology is similar to that of the adult, as it is also the case for most other polychelidan fossils.In this situation, as noted for Hellerocaris, the occurrence of a small juvenile seems incompatible with an ontogeny including an eryoneicus larva, because they are far smaller than most eryoneicus larvae.Yet, it is possible to imagine the existence a very small eryoneicus larva in the ontogeny of these species.However, such small larva would not be the equivalent of the giant eryoneicus larvae of the extant polychelids, which probably allow dispersion on long distances and a substantial part of the growth to occur among plankton.is absence of giant eryoneicus larvae further justifies the assignment of H. falloti to stem-Polychelidae (instead of Polychelidae sensu stricto) and suggests that eryoneicus larvae probably evolved later in the evolutionary history of polychelidan lobsters.Finally, it seems probable that development through eryoneicus larva can be retained as a defining character of Polychelidae.

PALAEOECOLOGY
Extant polychelids are blind and live principally at great depths (up to 6000 meters: Galil 2000).Fossil polychelidan lobsters are more diverse, so far all known species seem to have had developed eyes, and seem to have inhabited more diverse Audo D. et al. palaeoenvironments.Polychelidans from Lyme Regis or Holzmaden probably lived in rather deep palaeoenvironments.ose from "Solnhofen-type" plattenkalks and from Monte Fallano (Bravi et al. 2014) lived in shallower conditions.e La Voulte Lagerstätte preserves perhaps one of the deepest palaeoenvironment yielding fossil polychelidans (Charbonnier et al. 2007a(Charbonnier et al. , 2010)).
e La Voulte polychelidan community (Fig. 11) is dominated by P. giganteus (c.48% of studied sample), the second species in term of abundance is H. falloti (c.22%) and the third is W. ovalis (c.13%).ese three species (and also C. romani n. sp.) are probably autochthonous of the depositional environment as all comprise specimens of different sizes suggesting different growth stages preserved in their habitat.Eryonids are less abundant with Eryon ellipticus (c.7% of studied samples), followed by C. romani n. sp.(c.6%), V. parvulus n. gen., n. sp.(c.2%) and A. fourneti n. gen., n. sp.(c.1%).Due to the absence of juveniles of E. ellipticus, this species may be considered as parautochthonous.
e occurrence of P. giganteus supports the hypothesis that the La Voulte Lagerstätte preserves a deep sea palaeoenvironment.Indeed, there are several further indications that Proeryon is a deep-sea dwelling genus: 1) eyes in Proeryon are rather large compared to that of most other polychelidans; 2) other species of Proeryon co-occur with large pelagic marine reptiles such as ichthyosaurs and plesiosaurs (e.g., fragments of P. hartmanni (Meyer, 1836), have been discovered in the gut content of an ichthyosaur; Eudes-Deslongchamps 1868); and 3) Proeryon is probably one of the longest living genera of polychelidan lobsters, since it occurs from the Toarcian to the Hauterivian (Schweigert & Herd 2010), such a longevity may have been favoured by the relative stability of deep-sea palaeoenvironments, less prone to perturbations due to eustatic oscillations.e diet of extant polychelids is not well known, but at least two feeding habits can be identified: an opportunistic diet such as that Willemoesia forceps (Willemoes-Suhm, 1875), which gut content contains siliceous sponges, fibres of wood, foraminifera, remains of fishes (Firth & Pequegnat 1971;Gore 1984); and probably a more predatory diet such as Polycheles typhlops Heller, 1862 which feeds on small crustaceans such as euphausiaceans, mysidaceans, amphipods and isopods (Lagardère 1973).Differences in feeding habits are probably linked to the available food.e opportunistic diet of Willemoesia forceps is undoubtedly a result of the scarcity of food in its extremely deep environment (c.3400-4000 m; Gore 1984).On the other hand, Polycheles typhlops occurs in a shallower environment (600-1300 m; Lagardère 1973) and probably beneficiates from a greater abundance of prey.Cartes & Sardà (1992) noted that concentration of brittles stars in deep see environments marked eutrophic conditions.La Voulte Lagerstätte, with its extremely abundant brittle star populations and general density of fossil probably correspond to an eutrophic palaeoenvironment sufficiently rich for polychelidans to adopt a predatory diet.In this respect, the long first chelipeds of Proeryon giganteus, Willemoesiocaris ovalis and A. fourneti n. gen., n. sp. were probably well suited to catch small nectobenthic prey.
Willemoesiocaris ovalis is characterized by extensively long and slender first pereiopods, a wide scaphocerite, rather long uropods and large eyes.All these characteristics suggest that Willemoesiocaris was probably nectobenthic (i.e.swimming near the sea-bottom) and was probably able to hunt in the water column.PERSPECTIVES e present study expands our knowledge on the palaeobiodiversity of the La Voulte Lagerstätte, almost doubling the number of polychelidan species and allows to formulate a palaeoecological hypothesis.
A new municipal museum was scheduled to open in La Voulte. is museum could have been able to distribute scientific knowledge on La Voulte and organise a new excavation campaign.Given the concentration of fossils in La Voulte and the exquisite preservation, knowledge of the Jurassic polychelidan lobsters would surely have beneficiated of these new scientific excavations.
However, recent changes in the municipal administration and budget cuts led to the cancelation of this project.
ETYMOLOGY.-Combination of the Latin adamas, adamantis (= diamond), alluding to the shape of the outline of carapace, reminiscent of the outline of a traditional diamond cut.e gender of the genus is masculine.TYPE SPECIES.-Adamanteryon fourneti n. sp.INCLUDED SPECIES.-Only the type species is known.DIAGNOSIS.-Monospecific genus, as for type species.
FIG. 11. -Column chart comparing the major Lagerstätten yielding polychelidans in term of specific, generic and family rank diversity.
and do not indicate high taxonomic ranks. ).
Genus Voulteryon n. gen.ETYMOLOGY.-Combination of La Voulte-sur-Rhône (type locality) and Eryon Desmarest, 1817, generic name for the first described species of Eryonoidea.e gender of the genus is masculine.TYPE SPECIES.-Voulteryon parvulus n. sp. by monotypy.INCLUDED SPECIES.-Only the type species is known.DIAGNOSIS.-As for type species.
INCLUDEDSPECIES.-Only the type species is known.DIAGNOSIS.-As for type species (monospecific genus),.