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The higher taxonomy and evolution of Decapoda (Crustacea)

1981; Volume: 19; Issue: 17 Linguagem: Inglês

0080-5947

Martin D. Burkenroad,

Marine and fisheries research

The decapods are herein divided into four suborders: Dendrobranchiata, Euzygida, Eukyphida, and Reptantia. Evidence for monophyly of these taxa is supplied by the adult morphology of characters of gill arrangement, modes of pleopodal incubation, patterns of overlap of abdominal pleura, pleural lock and hinge arrangements, chelation of legs, presence of appendix interna, and form of spermatozoa; the fossil record; and ontogeny. Some possible lines of investigation are outlined which might yield a more natural classification within the Eukyphida and Reptantia. The difficulty in devising a satisfactory general classification for the Decapoda arises from doubts concerning the higher relationships of the numerous well defined and more or less isolated groups relatively low in the taxonomic hierarchy. For ex­ ample, Peneidea, Stenopodidea, and Caridea are regarded by Holthuis (1955) as mem­ bers of a supersection Natantia of the suborder Macrura, which he distinguished from two other suborders Anomura and Brachyura. This classification was derived from Bouvier (1917) and Milne-Edwards (1837). The same three groups (Peneidea, Stenopodidea, and Eucyphidea) are regarded by Balss (1957) as forming the suborder Natantia, while the remaining decapods are grouped together as Reptantia (more or less after Borradaile, 1907; Ortmann, 1892a, 1892^?, 1892c; and Boas, 1880). Glaessner (1960), a paleontologist, divides the same three groups between two different suborders. The Penaeidea and Stenopodidea together with reptant Nephropsidea form a suborder Trichelida, while the Caridea together with the reptant Thalassinidea and Paguridea form an infraorder Anomocarida of the suborder Heterochelida (the other infraorders being Palinura, Anomura, Brachyura, and the Glypheocarida). This is a modification of an earlier scheme proposed by Beurlen and Glaessner (1930). Gurney (1942) also restricted Natantia, placing the Euphausiacea among the Decapoda and the Stenopodidea among the Reptantia. Burkenroad (1963a) divided the natant groups still differently. Peneids and sergestids were placed in the suborder Dendrobranchiata while the Caridea and Stenopodida were placed with the other decapod groups in the sub­ order Pleocyemata, an arrangement essentially followed by Glaessner (1969). The view of this paper is that the Decapoda are monophyletic and distinct from the Euphausiacea, but that most previous subordinal arrangements of the decapods are polyphyletic. It is suggested that the three traditional groups are not at all closely related to each other and must be regarded as three independent suborders comparable to the fourth homogeneous suborder, Reptantia. It is further suggested that the Reptantia are naturally divisible into several maj6r groups, with the brachyuran forms distinct from all the rest. Within the non-brachyuran Reptantia, thalassinideans seem to be quite distinct from the anomuran, astacuran, and palinuran reptants and are treated in this paper as an independent supersection equal in status to the other three macruran and anomuran supersections. The presence of chelate legs in the early Triassic reptant Clytiopsis seems to imply that differentiation within the Reptantia by the development of chelae was already then