Taxonomy of the freshwater crabs of Costa Rica, with a revision of the genus Ptychophallus Smalley, 1964 (Crustacea: Decapoda: Pseudothelphusidae) Author Magalhães, Célio Author Wehrtmann, Ingo S. Author Lara, Luis Rólier Author Mantelatto, Fernando L. text Zootaxa 2015 3905 3 301 344 journal article 42408 10.5281/zenodo.235127 16b434af-bed4-43fd-bdfc-0f29bcaec7bb 1175-5326 235127 4DA803F1-30C6-4FC3-8EEF-9690A89822A6 Allacanthos Smalley, 1964 Pseudothelphusa ( Allacanthos ) Smalley, 1964b : 8 Type species . Allacanthos pittieri ( Rathbun, 1896 ) [by original designation]. Diagnosis . Exognath of third maxilliped between 0.6 to 0.7 times the length of endognath ischium. G1 straight, spermatic channel emerging on cephalic side; subdistal portion of mesio-cephalic, lateral sides with field of minute spines; marginal suture on mesial side, straight along most of stem; marginal process simple, short; distal part with large mesial lobe, narrow lateral lobe; field of apical spines weakly developed on internal surface of lateral lobe. Distribution . The species of this genus are distributed in southeastern Costa Rica and western Panama , Pacific drainage. Remarks . The relationships with other pseudothephusid genera, inferred by the G1 morphology, were discussed by Rodriguez (1982) .