Munnidae

Abstract: This paper presents a new phylogenetic estimate of isopod crustaceans of the suborder Asellota with the aim of clarifying the evolution of the superfamily Janiroidea, a large and diverse group inhabiting all aqueous habitats. The phylogenetic analysis is based on a morphological evaluation of characters used in past classifications, as well as several new characters. The evolutionary polarity of the characters was determined by outgroup analysis. The characters employed were from the pleopods, the copulatory organs, the first walking legs, and the cephalon. The resulting character data set was analyzed with numerical phylogenetic computer programs to find one most parsimonious clado-gram, which is translated into a classification using the sequencing convention. The new phylogenetic estimate is significantly more parsimonious than previous trees from the literature, and several of its monophyletic groups have robust confidence limits. The superfamily Stenetrioidea belongs to the clade including the Janiroidea, not with the Aselloidea as previously suggested. The sister group of the Janiroidea is the family Pseudojaniridae, which is elevated to superfamily rank. The clade including the families Gnathostenetroididae and Protojaniridae is not the sister group of the Janiroidea, and is derived earlier in janiroidean evolution than the Stenetrioidea. Within the Janiroidea, the family Janiridae is not the most primitive taxon as previously believed. The clade including the families Munnidae and Pleurocopidae contains the earliest derived janiroideans. The data also indicate that the unusual sexual morphology of the Janiroidea did not appear suddenly but developed as a series of independent steps within the Asellota.

Abstract: It is nearly a truism that in the deep-sea benthos supraspecific taxa tend to be cosmopolitan. As a result, additional sampling only rarely yields radically new morphological types, even in poorly studied parts of the ocean. As an unusual exception to this rule, two adjacent stations in the equatorial Atlantic, made on "Atlantis II" cruise no. 31, were found to be populated by two species of paraselloid isopods which are quite aberrant in their general body and limb form. The unusual morphologies exhibited by these species clearly require the definition of new genera, Abyssaranea and Thylakogaster, to contain them. These genera have restricted distributions despite the fairly extensive sampling in the Atlantic that has taken place in the past decade. Thylakogaster has appeared in only three different areas, and only once on the extensively sampled Gay HeadBermuda transect (Sanders et al., 1965; Hessler & Sanders, 1967). Abyssaranea at present is known only from the Equatorial Atlantic, and Munella was known prior to this paper, which records it from Bermuda, from the Bay of Biscay and the Mediterranean Sea (Bonnier, 1896; Lo Bianco, 1930). This patchy geographic distribution probably cannot be explained by some unusual geographic isolating factor since the stations listed in this paper yielded other Paraselloidea more com­ mon to the deep-sea fauna. One can only speculate on possible ecological factors that may be affecting the distributions of these genera. Thylakogaster tends to be badly fragmented during collection so that there may have been potential past records which were not reported due to the unrecognizable condition of the maiterial. It is probable that more careful sampling in other areas will bring to light more populations and species of the genera described herein, though they might not prove to be cosmopolitan as are many deep-sea isopod genera. These species do belong to a confusing cluster grouped within the families Munnidae and Dendrotionidae. Our inability to satisfactoril y include the genera of this paper in any of these families, as presently defined, documents the great need for a general revision. However, such an effort is beyond the scope of the present study and will be attempted in a future paper. Methods for collection and for preparing the taxonomic descriptions can be