The Reclassification of Brachyuran Crabs (Crustacea: Decapoda: Brachyura)

NAT. CROAT. VOL. 14 Suppl. 1 1¿159 ZAGREB June 2005 THE RECLASSIFICATION OF BRACHYURAN CRABS (CRUSTACEA: DECAPODA: BRACHYURA) ZDRAVKO [TEVÎ] Laco Sercio 19, HR-52210 Rovinj, Croatia [tev~i}, Z.: The reclassification of brachyuran crabs (Crustacea: Decapoda: Brachyura). Nat. Croat., Vol. 14, Suppl. 1, 1–159, 2005, Zagreb. A reclassification of brachyuran crabs (Crustacea: Decapoda: Brachyura) including a re-ap- praisal of their whole systematics, re-assessment of the systematic status and position of all extant and extinct suprageneric taxa and their redescription, as well as a description of new taxa, has been undertaken. A great number of new higher taxa have been established and the majority of higher taxa have had their systematic status and position changed. Key words: brachyuran crabs, Crustacea, Decapoda, Brachyura, systematics, revision, reclassification. [tev~i}, Z.: Reklasifikacija kratkorepih rakova (Crustacea: Decapoda: Brachyura). Nat. Croat., Vol. 14, Suppl. 1, 1–159, 2005, Zagreb. Reklasifikacija kratkorepih rakova (Crustacea: Decapoda: Brachyura) odnosi se na preispitivanje cjelokupnog njihovog sustava, uklju~uju}i preispitivanje sistematskog statusa i poloàja sviju recentnih i izumrlih svojti iznad razine roda kao i njihove ponovne opise. Uspostavljeno je mnogo novih vi{ih svojti, a ve}ini je izmijenjen sistematski status i poloàj. Klju~ne rije~i: kratkorepi raci, Crustacea, Decapoda, Brachyura, sistematika, revizija, reklasifikacija INTRODUCTION Brachyuran crabs (Crustacea: Decapoda: Brachyura) are one of the most diverse animal groups at the infra-order level. They exhibit an outstanding diversity in the numbers of extant and extinct taxa at all categorical levels. Recently, especially dur- ing the past several decades, judging from the number of publications and new taxa described, the knowledge of their systematics has increased rapidly. However, the data are very dispersed, written in various languages, and in publications that are often difficult to obtain. The rapid influx of knowledge concerning brachyuran Croatian Natural History Museum, Demetrova 1, Zagreb, Croatia 2 [tev~i}, Z.: The reclassification of brachyuran crabs taxa may be attributed to the increasing interest of scientists in the group. New expeditions, improved methods of sampling, a better knowledge of systematic charac- ters and systematic theories have also aided in this endeavour. The attention of specialists has been focused mostly on species and genera (alpha taxonomy). At the same time the higher-level systematics of the group, the suprageneric taxa (tribes, subfamilies, families and superfamilies) have been neglected by the majority of carcinologists, so much so that higher taxa have often remained vaguely delimited, imperfectly described and inappropriately arranged. The authors usually re-write the descriptions of higher taxa from ALCOCK (1895 – 1910), written more than a century ago, with little or no improvement, although theoretical and practical knowledge have advanced substantially. Rarely have new higher taxa been described. As such, new descriptions of higher taxa have often omitted their systematic status and position, with reclassification postponed to an indefinite future. One may see how some families have undergone complete revisions, while many others remain only partially revised or have never been revised at all. Thus, the historical devel- opment of brachyuran systematics has been very unbalanced, with prolific discov- eries of new species and genera and incompletely described suprageneric taxa. The result of this unbalanced research program is an imperfect brachyuran classification. Systematic study of the crabs as a whole also remains incomplete and imperfect and therefore revision on all levels awaits a better time. In the recent systematic literature the most frequent phrase is »a revision is badly needed«. All authors working on brachyuran systematics invariably agree that a general revision of the whole group is urgently needed, yet nothing has been done to accomplish it. Many carcinologists are conscious of the need for general revision, like, for example, Austin WILLIAMS, who in his letter to the author of Oct. 31, 1989 wrote: »The higher categories are ill defined. Many accepted definitions are nothing more than central tendencies around which are clustered conformers to those tendencies, but in many cases around which are appended the exceptions as well. Conservativism militates against creation of many small families or other higher subdivisions of the hierarchy to accommodate these problems in classification. The expert comes to know the labyrinthine structure, recognizes the dead ends, blind loops, deceptive paths, appended detours, i.e. the exceptions, and ac- cepts these because redesign with aid of the tools available (morphology until now) is a daunting task«. To accomplish such a research project, it is necessary to per- form three things: firstly to compile all up to date data on the suprageneric brachyuran, secondly, to critically re-examine the homogeneity, systematic status and position of all suprageneric taxa, and thirdly, to propose a new, updated system of classification. Unfortunately at this time no such comprehensive compilation exists. On the other hand every year produces many new lower taxa with only a temporary classification or often without attempts at any classification of the newly described taxa into a natural system. The result of such a practice is a chaotic state-of-the-art in brachyuran systematics. So many unresolved problems concerning brachyuran systematics have accumulated over the years that a project of complete revision will take an immense effort by experts. Due to the time-consuming nature of data compilation, their synthesis and critical reassessment, conspectus of Nat. Croat. Vol. 14, Suppl. 1, 2005 3 the brachyuran classification in the past has been extremely rare. BLACKWELDER (1967:98) is correct when he claims: »The studies which deal only with the grouping of ani- mals and the arrangement of the groups into categories of the hierarchy are not very numerous«. The complete revision of the brachyuran higher taxa has been indeed »a daunting task«! It is a matter of fact that research into the brachyuran system is confronted with subjective as well as objective circumstances. It is understandable that leading specialists working in the great museums, in spite of all the favourable facilities (collections, libraries and technical help), tend to avoid a general revision of the entire brachyuran systematics, which requires many years of painful study, and that they cannot find the time for such projects. It is also fact that they have large collections (usually sampled by expeditions) so that they have focused their attention on in- vestigations of their own museum material, describing new species and genera, and seldom touching on the problems of higher classification. So much material has been accumulated that the specialists employed are hardly able to deal with this properly. Moreover, the number of scientists occupied with research into brachyuran crabs (specialists and technical staff) in museums has recently been reduced and collections are not arranged according to current brachyuran systematics. Nu- merous revisions have not been applied to the museum specimens. For example, although the genus Pilumnoplax Stimpson, 1858 (Goneplacidae sensu Balss, 1957) is invalid, in many museum collections all around the world, specimens are still la- belled under this name. Furthermore, museum collections are often in bad condi- tion because of reduced staff. There are often cases where the names of genera and species were changed but the labels were not changed for a long time so that any orientation in these museums became very difficult. For example I have found four different Heterocrypta petrosa Klunzinger, 1906 (Parthenopidae) in various museums, but the name was not correct for any of the four. Moreover, some genera are not at all classified, or only partially classified so that they are placed in a family without precise designation of subfamily or tribe, or some genera are classified into a subfamily, but the family is not denoted. On the other hand it is surprising (and nearly fashionable) that many modern authors in their revisions give neither diagnoses nor descriptions of the higher taxa under study, which makes further classification difficult. Discussions are frequently omitted or, if present, they are often confusing rather than clarifying. Furthermore, many proposed systematic changes are not supported by valuable data such as descriptions rather than by subjective opinions. For example it is clear that if a subfamily is excluded from one family and trans- ferred into another so that both families changed their previous contents, then both should be re-described. All the problems mentioned above make it difficult to draw any further important generalisation from such studies. In the larger works (mono- graphs) the authors usually reiterate more or less modified descriptions from the old authors that have been used for a century and therefore these descriptions are inappropriate (e.g. Oxyrhyncha, Oxystomata, Goneplacidae). The accumulated problems that I have outlined above have all contributed to the postponement of general revision. Consequently, the general critical re-examination of all brachyuran taxa is indeed urgently needed. 4 [tev~i}, Z.: The reclassification of brachyuran crabs HISTORICAL BACKGROUND

Load more