Contributions to Zoology, 68 (2) 109-141 (1999)Araujo Paula Beatriz; Andreas Leistikow: Philosciids with pleopodal lungs from Brazil, with description of a new species (Crustacea, Isopoda)

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Phylogenetic relationships

The three genera discussed above share several characters. Due to the lack of an elaborate phylogenetic analysis of the Criochaeta and, thus, the lack of a ground plan it is quite difficult to interpret several characters, e. g., the status of the pectinate teeth of Benthana. All species bear rather big compound eyes, which is a plesiomorphic character compared to other Oniscidea. By virtue of the shape of the antennal organ these species are excluded from the monophyletic group to which Ischioscia and several other genera belong (cf. Leistikow, in press); most probably this character is also plesiomorphic. Nonetheless, some characters indicate a close relationship of Benthana to Atlantoscia, i.e., the shape of the maxilla with the lateral lobe apically concave, the position of the noduli laterales is gradually more dorsal from coxal Fig. I to IV, then steeply narrows the lateral border on coxal plate V.

Both genera seem to have some relationship to Balloniscus, although they are more distant from that genus than they are from each other. In particular Benthana has similar carpal brushes in the males on pereiopod 1 to 3. Since similar carpal brushes occur in other genera, it is important to stress the similarity even in the shape of the sensory spines forming these brushes, e.g., totally different to those seen on Ischioscia, which bears carpal brushes formed by cuticular scales instead of sensory spines. For the evidence of a postulated synapomorphy of Benthana and the Balloniscidae, a re-examination of the second genus of Balloniscidae, Plataoniscus Vandel, 1963, is desirable. However, the treatment of Plataoniscus and Balloniscus as a family on its own is unsatisfactory, since covered pleopodal lungs occur in the Afrotropical genus Aphiloscia, and even in Atlantoscia rubromarginata sp.n., their respective closest relatives lack such respiratory organs. Until the phylogenetic relations can be established, the Balloniscidae should be lumped within the paraphyletic “Philosciidae.” In this regard the following should be mentioned. The dentation of the lateral endite of the maxillula is quite similar in Balloniscus and the southern populations of A. floridana. This feature could represent a synapomorphy of these genera.

In the genera dealt with, the pereiopods structurally resemble those of Aphiloscia. However, at the present state of knowledge it is not clear if these characters could support any close relationship of all these genera. In particular, there is no biogeographic evidence for a close relationship; Aphiloscia is of mainly East African in distribution. However, it is remarkable that all genera discussed above are mainly of East Brazilian distribution and found in the Atlantic region (Lemos de Castro, 1976, Ferrara & Taiti 1981, Taiti & Ferrara 1991) (Fig.23). The fauna of this region is related to the Afrotropical region although both tectonic plates have been separated since the Late Cretaceous (Emiliani, 1995). So it can not be excluded that there exists an ancient connection between the Brazilian and African genera. Although the philosciid genera of the African tropics are rather well-studied (Schmalfuss & Ferrara 1978, Taiti & Ferrara, 1980), it is too early to establish phylogenetic relationships between those genera.

FIG2

Fig. 23. Known distribution of philosciid genera dealt with in this work.