Guinot, D., Jamieson, B.G.M., Richer de Forges, B. and Tudge, C.C. 1998a. Comparative spermatozoal ultrastructure of the three dromiacean families exemplified by Homolodromia kai (Homolodromiidae), Sphaerodromia lamellata (Dromiidae), and Dynomene tanensis (Dynomenidae) (Podotremata: Brachyura). Journal of Crustacean Biology 18, 78-94.
The monophyletic Dromiacea, including Sphaerodromia lamellata, Homolodromia kai, and Dynomene tanensis, here studied, have the following characters: (1) operculum perforate, but lacking the thoracotreme apical button; (2) opercular projections into the subopercular material, diagnostic of homolids, absent; (3) operculum discontinuous with the capsule, unlike raninoids; (4) operculum moderately thick, not extremely thin as in the cyclodorippoids Tymolus and Xeinostoma; (5) operculum not extremely wide, contrasting with the great width in cyclodorippoids; (6) periopercular rim and (7) accessory opercular ring absent, being variably present in eubrachyurans; (8) subopercular protuberance through operculum well developed (synapomorphy), weak in homolids; (9) true acrosome ray zone absent; (10) peripheral border of outer acrosome zone border not ragged, unlike some xanthoids; (11) anterolateral pale zone of acrosome contents present (autapomorphy); (12) xanthid ring absent; (13) subacrosomal chamber or perforatorium extending preequatorially, unlike Ranina ranina; (14) head of perforatorium bilateral (autapomorphy); (15) corrugations of the wall of the perforatorial chamber absent; (16) centrioles apparently absent; (17) posterior median process of the nucleus absent; (18) thickened ring (typical of Eubrachyura) absent; (19) concentric lamellae (typical of Thoracotremata) in the outer acrosome zone absent; (20) capsular chambers absent; and (21) capsular flange absent, unlike Ranina ranina and Raninoides sp. Spermatologically Sphaerodromia lamellata appears closer to the dynomenid Dynomene tanensis than it is to the mutually paraphyletic Dromidiopsis edwardsi and Stimdromia lateralis. The spermatozoon of Homolodromia kai (Homolodromiidae) shares a striking putative synapomorphy with Paradynomene tuberculata: a flange-like lateral extension of the lower acrosome zone; both species appear to lie within a dromiid clade. Neither the Dromiidae nor the Dynomenidae appear monophyletic spermatologically. The spermatozoal evidence is discussed in the light of a brief review of nonspermatozoal morphology. General morphology and spermatozoal ultrastructure both strongly endorse monophyly of the Dromiacea.