Updated key to genus Parastacus. The following key is modified from Huber et al. (2022), with the addition of Parastacus longidactylus sp. n. 1 Telson with lateral spines ................................................................................................................................... 2 1’ Telson without lateral spines, maxilliped III exopod flagellum surpassing ischium distal margin..... ....................................................................................................................... Parastacus nicoleti (Philippi, 1882) 2(1) Postorbital carina proximal edge ending in a strong spine; uropod protopod proximal lobe bearing a spine; areola delimited by carinae ................................................................................................................ 3 2’ Postorbital carina proximal edge not ending in spine; uropod protopod lobe lacking spine; areola not delimited by carinae ............................................................................................................................................ 4 3(2) Cheliped merus,carpus,and propodus medially with tufts of long setae; maxilliped III ischium ventral margin with longitudinal spine row ...................................................... Parastacus varicosus Faxon, 1898 3’ Cheliped merus, carpus, and propodus medially glabrous; maxilliped III ischium ventral margin with longitudinal tubercle row ............................................................................. Parastacus saffordi Faxon, 1898 4(2’) Telson distal margin rounded............................................................................................................................ 5 4’ Telson distal margin acute ................................... Parastacus buckupi Huber, Ribeiro and Araujo, 2018 5(4) Cheliped carpus distally glabrous .................................................................................................................... 6 5’ Cheliped carpus distally with tufts of long and simple setae ....................................................................... .................................................................................. Parastacus pilicarpus Huber, Ribeiro and Araujo, 2018 6(5) Epistome anteromedian lobe hexagonal or pentagonal .............................................................................. 7 6’ Epistome anteromedial lobe septagonal ......................................................................................................... 8 7(6) Cheliped dactyl and pollex cutting edges covered by long setal tufts...................................................... 9 7’ Cheliped dactyl and pollex cutting edges visible ........................................................................................10 8(6’) Dactylus long .................................................................................................... Parastacus longidactylus sp. n. 8’ Dactylus short ......................................................... Parastacus gomesae Huber, Araujo and Ribeiro, 2022 9(7) Postorbital carinae prominent ............................................... Parastacus pilimanus (von Martens, 1869) 9’ Postorbital carinae obsolete ............................................. Parastacus laevigatus Buckup and Rossi, 1980 10(7’) Chelipeds with globose palm .......................................................................................................................... 11 10’ Chelipeds with flattened palm ....................................................................................................................... 13 11(10) Cervical groove U-shaped .... Parastacus caeruleodactylus Ribeiro and Araujo in Ribeiro et al., 2016 11’ Cervical groove V-shaped ............................................................................................................................... 12 12(11’) Rostral carinae reaching postorbital carinae proximal edge ............. Parastacus defossus Faxon, 1898 12’ Rostral carinae surpassing postorbital carinae proximal edge ... Parastacus pugnax (Poeppig, 1835) 13(10’)Telson subrectangular ...................................................................................................................................... 14 13’ Telson subtriangular .......................... Parastacus fluviatilis Ribeiro and Buckup in Ribeiro et al., 2016 14(13) Cheliped palm dorsal surface with tubercles irregularly distributed .................................................... 15 14’ Cheliped palm dorsal surface with three well-defined tubercle rows ........................................................ ........................................................ Parastacus tuerkayi Ribeiro, Huber and Araujo in Ribeiro et al., 2017 15(14) Cheliped ventral surface bearing one row of squamose tubercles ......................................................... 17 15’ Cheliped ventral surface bearing two rows of squamose tubercles ....................................................... 16 16(15’)Postorbital carinae prominent in anterior and middle portions .................................................................. ........................................................................................ Parastacus guapo Huber, Araujo and Ribeiro, 2022 16’ Postorbital carinae weakly prominent................................................................................................................ ............................................................... Parastacus macanudo Huber, Rockhill, Araujo and Ribeiro, 2020 17(15) Cheliped palm medial margin tuberculate, cervical groove U-shaped ...................................................... ........................................................................................ Parastacus promatensis Fontoura and Conter, 2008 17’ Cheliped palm medial margin smooth; groove weakly V-shaped ............................................................... ...................................................................................................... Parastacus brasiliensis (von Martens, 1869)

Published as part of Huber, Augusto Frederico, Araujo, Paula Beatriz de & Ribeiro, Felipe Bezerra, 2024, A new freshwater crayfish species of Parastacus Huxley, 1879 (Malacostraca: Decapoda: Parastacidae) from southern Brazil, pp. 1-17 in Nauplius (e 20230496) (e 20230496) 32 on pages 13-14, DOI: 10.1590/2358-2936e20230496, http://zenodo.org/record/10716860