MARESFE GAMMARIDEAN AMPHIPODA 21 



6, Melita 5, Metopa 7, Monoculodes 4, Oediceroides 11, Onesimoides 3, Orchomene 

 14, Proboloides 7, Pseudharpinia 5, Schisturella 5, Stegocephaloides 5, Stenothoe 

 4, Syrrhoe 5, Syrrhoites 8, Tryphosella 20, Unciola 6 (Atlantic boreal), Uristes 

 11, Urothoe 5. 

 Demersal?: Aristias 8, Astyra 5, Cleonardo 8, Eurythenes* 2, Eusirus 9, Halice 

 8, Lepechinella 13, Pseudotiron 3, Rhachotropis 20, Valettiopsis 3. 



Morphological Evolution of the Amphipoda 



Amphipoda comprise four unusual suborders: (1) the Gammaridea, 

 primarily benthic, mth perhaps 20 percent pelagic and demersal 

 species, but having apparently radiated a half dozen or more times 

 into a gradational suborder, (2) the Hyperiidea, marked by fully 

 pelagic (free or inquihnous) habits, the strange but universal loss of 

 maxiUipedal palp, and a spectrum of other minor changes presumably 

 correlated with their habits; perhaps from podocerid gammarideans 

 have evolved (3) the Caprellidea, skeleton shrimps or marine praying 

 mantises, characterized by extremely thin tubular bodies, reduction 

 in abdomen, reduction in two pairs of pereopods, increased cephah- 

 zation and primarily adapted to a sedentary hfe in epifaunal anas- 

 tomoses; but through secondary body depression within the caprelh- 

 dean scheme (like Temnophlias in the gammaridean scheme) arose 

 the cetacean ectoparasites Cyamidae, essentially comprising a fifth 

 major group of Amphipoda; and finally (4) the Ingolfiellidea, appar- 

 ently undergoing development in association with troglobitic condi- 

 tions but occasionally returning to marine niches yet open to those 

 organisms with vestigial pleopods, often bearing cephahc "ocular" 

 scales and with, perhaps, other special ecological adaptations. 



Even though Amphipoda have radiated into nearly 60 families 

 the major diversity can probably be visuahzed in terms of a score 

 of kinds. These typological centers may be described by the following 

 adjectives: ingolfiellid, cyamid, caprellid, six to eight kinds of hyperiid, 

 gammarid, eusirid, isaeid, lysianassid, colomastigid, eophhantid, phli- 

 antid, tahtroid, stenothoid, amphilochid-leucothoid, ampeliscid, and 

 acanthonotozomatid. Some outgrowths of these centers form radical 

 morphs but they fail to quahfy as typological centers because (1) 

 their relationships are not discontinuous or (2) they have not radiated 

 strongly. The Cheluridae are an example of a radical morph with 

 presumed relationships to the Isaeidea and low internal diversity; 

 they are not considered as a typological center. The Colomastigidae, 

 though of low diversity, have discontinuous relationships with other 

 Amphipoda and are, therefore, considered as a typological center. 

 The eusirids (not necessarily the type-genus) have clear relationships 

 to another center but have radiated so strongly that they must be 

 considered a typological group. My concept of these centers on cur- 



