Dawsonius Manning and Felder 1991
Creators: name: Poore, Gary C. B.
name: Dworschak, Peter C.
name: Robles, Rafael
name: Mantelatto, Fernando L.
name: Felder, Darryl L.
Publisher: name: Zenodo
Year: 2019
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Callianassidae
Dawsonius

description: Dawsonius Manning and Felder, 1991   
 Dawsonius Manning and Felder, 1991: 785.— Sakai, 2005b: 245.— Sakai, 2011: 508.   
 Gourretia.— Sakai, 2017a: 1128–1129 (partim).   
 Type species. Callianassa latispina Dawson, 1967, by original designation and monotypy.   
 Diagnosis. Cardiac prominence present. Rostrum sharply triangular, produced to near apex of ocular lobes. Pleomere 6 with lateral projections. Male major cheliped merus with straight or weakly convex blade on lower margin bearing a short proximal curved spine and 1 or more distal spines; propodus rectangular, fingers fine, fixed finger smooth. Minor cheliped merus lower margin with erect proximal spine (as in major cheliped); propodus tapering, about 3 times as long as wide, with long narrow fingers. Pereopod 3 propodus triangular, with straight upper margin, expanded proximally on lower margin. Male pleopod 1 article 2 with lobed distomesial margin, distal notch, sharp curved distolateral apex. Telson parallel-sided over anterior half, then tapering to evenly rounded apex.   
 Remarks. Dawsonius latispina differs from other ctenochelids (except Paragourretia biffari Blanco Rambla and Liñero Arana, 1994) in having lateral projections on pleomere 6.   
 Manning and Felder (1991) differentiated Dawsonius from Gourretia on the absence of an exopod on maxilliped 3 and the sharp lateral projections on pleomere 6. We (DLF) can confirm that maxillipedal 3 exopod is absent (Dawson, 1967; Manning and Felder, 1991) and that Biffar’s (1971a) figure and Sakai’s (2011) observation of an exopod are in error. Biffar’s figures are a composite from types and Honduran material but the latter is P. biffari.   
 Sakai (2005b) treated the genus first as a synonym of Callianopsis and in an addendum as a separate genus that he differentiated from Callianopsis. Callianopsis is a member of another family. He did not explain what he meant by “sensu Sakai (not Manning and Felder, 1991)” before his new diagnosis. Sakai (2011) included Dawsonius in Gourretiidae. Sakai’s (2011) observations of a “ paratype ” and a “ lectotype ” (USNM 103755, 172310) were not made on the holotype and paratype designated by Dawson (1967); these specimens may well have been misidentified. Sakai’s (2011: fig. 69E) figure of the apex of the male pleopod 2 is impossible to reconcile with Manning and Felder (1991: fig. 16i), which is typical of the family, nor with any ctenochelid.   
 Sakai (2017a) synonymised Dawsonius with Gourretia on the basis of the same male pleopods 1 and 2. In fact, Dawsonius is unique in pleopod 1 possessing a distomesial rounded blade and acute apex, whereas in Gourretia and Paragourretia the distomesial lobed is acute and smaller than the apical lobe.
description: Published as part of Poore, Gary C. B., Dworschak, Peter C., Robles, Rafael, Mantelatto, Fernando L. & Felder, Darryl L., 2019, A new classification of Callianassidae and related families (Crustacea: Decapoda: Axiidea) derived from a molecular phylogeny with morphological support, pp. 73-146 in Memoirs of Museum Victoria (Mem. Mus. Vic.) (Mem. Mus. Vic.) 78 on page 119, DOI: 10.24199/j.mmv.2019.78.05, http://zenodo.org/record/12214175