REVIEWS

H. P. WAGNER,1994. A monographic review of the Thermosbaenacea (Crustacea: Peracarida). A study on their morphology, taxonomy, phylogeny and biogeography. Zoologische Verhandelin- gen, Leiden, 291: 1-338, 500 figs., 11tabs. ISSN 0024-1652 or ISBN 90-73239-30-3. Available from Universal Book Services/Dr. W. Backhuys, Warmonderweg 60, NL-2341 KX Oegstgeest, The Netherlands, at NLG 160.- (approx. US$ 100.-, excl. VAT and P & P) or from the author, Dr. H. P. Wagner, Platanenrode 6, NL-2317 BT Leiden, The Netherlands, at NLG 130.- (approx. US$ 80.-, limited supply only). This book certainly constitutes the most important work devoted to the crustacean order Ther- mosbaenacea ever published. It is both a synthesis of what at present is known of the group and also the most important new contribution to the knowledge of Thermosbaenacea: 15 new taxa are described and reported in a group which is very widely distributed throughout the world, but which until the publication of Wagner's work included less than 20 known species. These new species are mainly from the West Indies, a region more extensively explored than others, especially by several field investigations performed during about 15 years by Dutch Speleological Groups often led by Prof. Jan Stock from Amsterdam, and also often with the active participation of H. P. Wagner who personally collected several new taxa. New species are also described from four different Mediterranean countries: Greece, Italy, France, and Spain. A good historical introduction (13 pp.) recalls the main steps of our knowledge of the group from its discovery in Tunisia in 1923, and the first publications by Prof. Th. Monod (1924) to the most recent report of Thermosbaenacea from Australia (1992). The author discussed the origin of the studied material from different parts of the world, and also the methods that he used, with special emphasis on a specific technique of cuticular colouration by Chlorazol Black B, a staining method necessary for accurate observation of chaetotaxy. The general morphology of thermosbaenacean crustaceans is presented (7 pp.) with some good figures, often modified from those of previous authors furthermore many references are given here to original figures prcsented in the taxonomic part of the text. Hereby the reader who is not a specialist of the group can obtain an exact idea of the morphology of Thermosbaenacea. The next chapter, of 15 pp., is devoted to the chaetotaxy of the thermosbaenaceans, as chaetotaxic characters are very often the main features used for the distinction of different species, and also the most useful characters available for phylogenetical analysis of the group. Several classifications have previously been proposed and several terms have been used for the same chaetotaxic structures (setae or scales or parts of such setae). Wagner here clearly exposes the meaning of the terms used in his work and proposes a terminology and a classification of setal types (modified from Watling's classification, 1989), well suitable for Thermosbaenacea. The main part of the book (258 pp.) concerns the systematics of the Thermosbaenacea, in- cluding the diagnosis of the order, the four recognized families (Thermosbaenidae, Monodellidae, Halosbaenidac, and Tulumellidae nov. fam.), the seven genera, and the 34 considered species, with the description of these species. This descriptive part includes new data concerning known species, especially those regarding a number of chaetotaxic characters not always detailed in orig- inal publications. It includes also the complete description of 15 new species. All descriptions are abundantly illustrated by large and clear figures, which are presented together in full page plates. 802

All these (440) figures are original and represent a considerable work which will remain a main reference in further studies on Thermosbaenacea. After the descriptive and systematic review, a first really phylogenetical approach to the Ther- mosbaenacea is presented, using the cladistic method. This approach (23 pp.) is global and modern: his data matrix includes the maximum number of descriptive characters, which are processed with the PAUP computer program of parsimony. The successive analyses are also performed in a logical order, aiming first at the identification of the most probable sister-group of the Thermosbaenacea among the 9 orders of Peracarida, with reference to the "caridoid supposed ancestor". Then, using this sister-group (the Mictacea) as an out-group and following the same method, the more parsimo- nious phylogenetic trees are constructed for the 7 genera of thermosbaenaceans, leading to a strict consensus tree and a majority-rule consensus tree for the order. Similar analyses have also been attempted with the species-groups forming the more diversified genera of the Thermosbaenacea, and the various trees are shortly discussed. The work ends with considerations (11pp.) concerning the origin and the biogeographic patterns of Thermosbaenacea, partly from the literature and also from the analyses presented by the author after the last discoveries of the nineties and his own results presented in the previous chapters. The final bibliography (11pp.) includes 271 references cited in the text and surely constitutes, as the text and figures of Wagner's book, the best basis for any further research dealing with thermosbaenaceans. As shown when considering the proportions of the different parts of the work (see the numbers of pages above mentioned) the most important chapter of the book certainly is the taxonomic part. It is probably the most important of Wagner's contributions to the knowledge of the Thermosbae- nacea, even if the preceding parts (historical introduction, general morphology and chaetotaxy of Thermosbaenacea) represent very useful chapters for students not yet familiar with the group and also for the authors of further descriptions. In this systematic part, among the main contributions of the author, it is necessary to mention: - An important increase of the number of known taxa of the order Thermosbaenacea, which is nearly doubled with 15 new taxa; - Several Mediterranean populations of Monodella from Italy, Croatia, and Greece which were considered as conspecific about 30 years ago, appear now as different species (argentarii, halopfiila and aiakos) of Tethysbaena, showing the endemism of Monodellidae to be more important than previously supposed; - The creation of the new genus Tethysbaena for all the species previously included in the genus Monodella, except for the type-species Monodella stygicola Ruffo, 1949, while several new species are described in Tethysbaena. The restriction of the now monotypic genus Monodella to M. stygicola seems acceptable, as is the creation of the widespread polytypic genus Tethysbaena. However, among the four diagnostic characters proposed by Wagner (p. 51) for the division of the family Monodellidae, three arc not completely convincing. The first of these is the number of segments of the main flagellum of the first antenna (10 in Monodella, variable from 6 to 12 in Tethysbaena), which actually is not really different. The second concerns the number of macrosetae on the carpus of the gnathopod (this number is said to be four in Monodella versus three in Tethysbaena as mentioned in the diagnoses of these genera on pp. 52 and 63). However, fig. 78 shows actually four macrochaetae on the carpus of the gnathopod of Monodella, fig. 103 shows only 2 setae on that carpus of T.juriaani, while this number is neither indicated in the descriptions nor visible in any of the figures of the 20-odd other species of Tethysbaena. Thirdly, the macrosetae on the second segment of the exopodite of pereiopod 5 (no medial and lateral macrosetae in Monodella, versus medial and sometimes vestigial lateral macrosetae in Tethysbaena): from figs. 82 and 107 it is clear that there is roughly the same chaetotaxy in the two genera, viz., four macrochaetae on the terminal exopodite segment in Monodella stygicola and also in Tethysbaena juriaani, the first seta of the terminal segment is only somewhat more lateral and smaller in T. juriaani than