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

Among Erymidae Van Straelen, 1925 (Van Straelen V. 1925. Contribution a l'etude des crustaces decapodes de la periode jurassique. Memoires de la Classe des Sciences de l'Academie royale de Belgique 7: 1-462), typical Mesozoic crustaceans, the genus Eryma Meyer, 1840 (Meyer H. von. 1840a. Briefliche Mittheilungen. Neues Jahrbuch fur 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 Munster, 1839 (Munster G. 1839. Decapoda Macrura. Abbildung und Beschreibung der Fossilen Langschwanzigen Krebse in den Kalkschiefern von Bayern. Beitrage zur Petrefaktenkunde 2: 1-88) (sensu Etallon [Etallon A. 1859. Description des crustaces fossiles de la Haute-Saone et du Haut-Jura. Bulletin de la Societe geologique de France 16: 169-205]), and Erymastacus Beurlen, 1928 (Beurlen K. 1928. Die Decapoden des Schwabischen 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 altesten 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.