Essai d'analyse critique des principales hypotheses concernant la phylogenie des Malacostraces (Crustacea, Malacostraca)

• Main Authors: Ionel Tabacaru, Dan L. Danielopol
• Format: Article
• Language: English
• Published: Editura Academiei Romane 2011-08-01
• Series: Travaux de l'Institut de Speologie Emile Racovitza
• Subjects: Crustacea; Malacostraca; Cladistics; Phylogeny.
• Online Access: http://www.speotravaux.iser.ro/11/art06.pdf
• ISSN: 0301-9187; 2067-9033

Malacostraca, as a Class, represents the largest taxonomic group within the Subphylum Crustacea. This essay is a contribution to the perennial debate of the way to classify the more than 40,000 malacostracan species. The various opinions on the way generations of carcinologists systematised Malacostraca in Orders and Superorders issynthetically reviewed. Because of the variety and contrasting opinions a reanalysis of the large carcinological data using a strict phylogenetic framework is presented. It is assumed that Malacostraca is a monophyletic group and within its system one deals, a priori,with monophyletic orders. With this assumption at hand a cladistic analysis of 17 orders and 68 morphological traits is presented. The analysis was done using the Wagner parsimony algorithm implemented in the computer programme PAUP 4.10. Based on 37 informative characters, an unrooted tree with a length of 101 steps was obtained. The results are discussed at long comparing the present data with diverse opinions on the phylogenetic affinities of the Malacostraca main groups. It is especially emphasised the significance of the present results for a new framework of the Malacostraca phylogeny and systematics. The following major conclusions emerge: (1) Phylocarida (Order Leptostraca) represents a basal group of Malacostraca separated early from its sister-group Eumalacostraca; (2) this latter group constitutes the major stock of Malacostraca; (3) the Syncarida does not represent a monophylum because Bathynelacea is a well individuated basal group of Eumalocostraca. Hence, it is proposed to accept the taxonomic solution of SERBAN (1970) who defined this group as the Superorder Podophalocarida; (4) the Hoplocarida is a collateral stem detached very early from the Eumalacostraca; it presents a mosaic of primitive and advanced (original) morphological traits; (5) the sister-group of Hoplocarida is formed by the bundle of lineages Anaspidacea + Neocarida + Eucarida,representing a major component of Eumalacostraca and which could be assimilated to thetaxon Caridoida (however, without including the Bathynellacea); (6) Anaspidacea is the only group of the Superorder Syncarida, the most primitive branch of the Caridoida s. str.; (7)Thermosbaenacea is a well individuated lineage, taxonomically ranked as Superorder Pancarida, the sister-group of the Peracarida; (8) the Neocarida (Pancarida + Peracarida)represents, most probably, the sister-group of Syncarida (Anaspidacea) and the bundle Syncarida + Neocarida forms the sister-group of Eucarida; (9) Amphipoda and Isopoda do not represent sister-groups; Amphipoda is a more primitive group having affinities to the bundle of lineages united in the taxon Mancoida; both taxa are sister-groups.