The genus Eryma Meyer , 1840 ( Crustacea : Decapoda : Erymidae ) : new synonyms , systematic and stratigraphic implications

This is anOp Abstract – Among Erymidae Van Straelen, 1925 (Van Straelen V. 1925. Contribution à l’étude des crustacés décapodes de la période jurassique.Mémoires de la Classe des Sciences de l’Académie royale de Belgique 7: 1–462), typical Mesozoic crustaceans, the genus Eryma Meyer, 1840 (Meyer H. von. 1840a. Briefliche Mittheilungen. Neues Jahrbuch für Mineralogie, Geognosie, Geologie und Petrefactenkunde 576–587) includes the largest number of species, mainly from Jurassic deposits. However, the lack of clear diagnoses for erymid genera has led to mistakes in generic assignments and to the establishment of redundant genera. The review of the concept of Eryma herein presents an attempt to clarify its diagnosis, mainly supported by the carapace groove pattern and the morphology of chelae of the first pair of pereiopods, and to emphasize its systematic implications. Thus, we maintain the synonymy of Klytia Meyer, 1840, Bolina Münster, 1839 (Münster G. 1839. Decapoda Macrura. Abbildung und Beschreibung der Fossilen Langschwänzigen Krebse in den Kalkschiefern von Bayern. Beiträge zur Petrefaktenkunde 2: 1–88) (sensu Étallon [Étallon A. 1859. Description des crustacés fossiles de la Haute-Saône et du Haut-Jura. Bulletin de la Société géologique de France 16: 169–205]), and Erymastacus Beurlen, 1928 (Beurlen K. 1928. Die Decapoden des Schwäbischen Jura mit Ausnahme der aus den oberjurassischen Plattenkalken stammenden. Palaeontographica 70: 115–278) with Eryma. Moreover, a review of the genera Protoclytiopsis Birshtein, 1958 (Birshtein JA. 1958. Ein Vertreter der ältesten Ordo der Crustacea Decapoda Protoclitiopsis antiqua gen. nov. sp. nov. aus dem Permo West-Sibiriens. Doklady Akademii Nauk, SSSR 122: 477–480), and Galicia Garassino and Krobicki, 2002 (Garassino A, Krobicki M. 2002. Galicia marianae n. gen., n. sp. (Crustacea, Decapoda, Astacidea) from the Oxfordian (Upper Jurassic) of the Southern Polish Uplands. Bulletin of the Mizunami Fossil Museum 29: 51–59), reveals the presence of a junction between the postcervical and branchiocardiac grooves. This feature is diagnostic of Eryma and supports the integration of these genera into the synonymy of Eryma. The addition of Protoclytiopsis to the synonymy of Eryma makes Eryma antiquum (Birshtein, 1958) nov. comb. the oldest representative of the genus and of the family, extending its stratigraphic range to the Late Permian (Changhsingian). Thus, this work also emphasizes that Erymidae crossed the Permian-Triassic boundary.

Currently, the carapace groove pattern of erymid lobsters is the main feature used for genera and species distinction (Van Straelen, 1925;Förster, 1966;Glaessner, 1969).However, the lack of clear generic diagnoses in the works of the nineteenth century and the different states of preservations of crustaceans has led to confusions about the concept of Eryma, and descriptions of redundant genera as consequences (Bolina Münster, 1839, Eryma and Klytia Meyer, 1840sensu Étallon [1859]).Such confusions persist nowadays but some recent works have attempted to bring clear elements for erymid lobsters discrimination (Hyžn y et al., 2015;Devillez et al., 2016).
This work aims to clarify the concept of Eryma on the basis of the carapace groove pattern and the morphology of the first pereiopod chelae.It also emphasizes systematic and stratigraphic implications of such clarification.

Material and methods
The studied material includes 42 specimens from the palaeontological collections of European institutions (Tab.1).Except fossils from the Solnhofen Lithographic Limestones, most of the studied specimens are fragmentary with only isolated carapaces or chelae preserved.They were mostly studied using a CETI Belgium MEDO binocular microscope.Line drawings were prepared by the first author.
The most recent diagnoses of Eryma proposed by Feldmann and Titus (2006), Hyžn y et al. (2015) and Feldmann et al. (2015) are relatively broad, particularly about the characteristics of the groove pattern.So, among the erymid lobsters, Eryma is the only genus exhibiting a junction between postcervical and branchiocardiac grooves.Other erymids such as Enoploclytia M'Coy, 1849 (Fig. 1F) and Pustulina Quenstedt, 1857 (Fig. 1G) show a reduced branchiocardiac groove only joined to dorsal margin, while it is well-developed and joined to the posterior extremity of the hepatic groove in Palaeastacus Bell, 1850 (Fig. 1D) and Stenodactylina Beurlen, 1928 (Fig. 1E) (Devillez et al., 2016).
Our examination of the photograph of the holotype of Protoclytiopsis antiqua reveals the presence of the typical grooves of the Erymidae: deep cervical groove, gastro-orbital groove present, postcervical and branchiocardiac grooves almost parallel.Moreover, the postcervical and branchiocardiac grooves are joined medially, as in Eryma (Fig. 2E-F).In conclusion, we consider Protoclytiopsis as a junior synonym of Eryma and the new combination Eryma antiquum (Birshtein, 1958) is herein proposed.Garassino and Krobicki (2002) erected the new genus Galicia with Galicia marianae (Oxfordian; southern Poland) as the type species.Most of the authors assigned this genus to the family Erymidae (Garassino and Krobicki, 2002;Schweitzer et al., 2010;Karasawa et al., 2013;Feldmann et al., 2015) while others included it in the family Clytiopsidae because of the absence of intercalated plate (Feldmann et al., 2012).Our review of the holotype indicates a carapace shape and a groove pattern typical of an Erymidae (subcylindrical carapace, deep cervical groove, gastro-orbital groove present, postcervical and branchiocardiac grooves almost parallel).Moreover, the carapace groove pattern exhibits the junction between the postcervical and the branchiocardiac grooves which is diagnostic of the genus Eryma (Fig. 2G-H).Hence, we consider Galicia to be a junior synonym of Eryma.
In addition, Galicia marianae exhibits a carapace with the following morphological characters: a wide branchial region, a well-marked gastro-orbital groove, subparallel postcervical and branchiocardiac grooves, slightly concave forward, a short branch extends the postcervical groove under its junction with branchiocardiac groove, a slightly inflated v area and a flat x area, an ornamentation made of fine tubercles.The carapace groove pattern and ornamentation are very similar to those of the well-known Eryma ventrosum (Meyer, 1835) from the Terrain à Chailles Formation (Oxfordian, Haute-Saône, France) (Meyer, 1840b;Bronn, 1851Bronn, -1852;;Étallon, 1859;Van Straelen, 1925;Charbonnier et al., 2012) (Fig. 2C-D).Hence, we consider G. marianae to be a junior synonym of E. ventrosum.
Addition of Protoclytiopsis Birshtein, 1958 to the synonymy of Eryma extends the stratigraphic range of the genus Eryma to the Late Permian (Changhsingian).Previously, Bachmayer and Malzahn (1983) had doubtfully assigned to Erymastacus a poorly preserved P1 chela from the Late Permian of Germany: Erymastacus (?) hoerstgenensis.As Schweitzer et al. (2010) regarded Erymastacus as synonymous with Eryma, they listed the species within representatives of Eryma.Later, Karasawa et al. (2013) removed the species from Erymidae because of its angular propodus and the shape of its fingers.Examination of the figure of the holotype of E. hoerstgenensis leads us to support the opinion of Karasawa et al. (2013).
Thus, Eryma antiquum (Birshtein, 1958) nov.comb., is the only erymid lobster reported in the Paleozoic and the oldest known representative of Eryma and Erymidae.
Finally, it is worth pointing out that the gap of almost 50 million years without reported Eryma between its two oldest representatives (E.antiquum nov.comb.from the Changhsingian and E. sinemuriana nov.comb.from the Sinemurian) shows the lack of fossils in the record of Eryma during the Trias.

Conclusions
A review of erymid genera leads us to consider Protoclytiopsis Birshtein, 1958, andGalicia Garassino andKrobicki, 2002, as junior synonyms of Eryma.Moreover, Galicia marianae Garassino and Krobicki, 2002, is herein considered to be a junior synonym of Eryma ventrosum (Meyer, 1835) on the basis of its carapace groove pattern and ornamentation.These additions into the synonymy of Eryma result in the extension of its stratigraphic range to Changhsingian (Late Permian).Thus, Eryma survived the Permian-Triassic mass extinction, commonly considered as the biggest of all major extinctions (Raup, 1979;Erwin, 1994;Stanley and Yang, 1994), with the occurrence of Enoploclytia gardnerae (Rathbun, 1935) in Mexican Paleocene deposits (Vega et al., 2007), it is worth noting that Erymidae also survived the Cretaceous-Paleogene mass extinction.However, E. gardnerae is the last occurrence of erymid lobsters in the fossil record so they are considered to be extinct.The presence of an intercalated plate, an exclusive character of Erymidae, was recognized by Schram and Dixon (2004) in members of the extant family Enoplometopidae (Saint Laurent, 1988).This observation leads us to question the link between Erymidae and Enoplometopidae.

Table 1 .
List of the examined material.