15 September 2009

Updated classification for the entire Crustacea Decapoda

Listing all known families and genera organized by higher taxonomic groups and including estimates of the number of species in every genus. Wow!
The introduction to this monumental work also sheds some light on the difficult issues involved in taxonomy.

Excerpts from the introduction:
It is a daunting task to compile a comprehensive list of the families and genera of the decapod crustaceans. Decapods are incredibly diverse, and decapod taxonomy is an active field with productive researchers constantly making new discoveries. These discoveries require changes in our classification in order to accommodate new findings and to better reflect evolutionary relationships. Thus, producing a complete and “up to date” classification of the decapods is in many ways an exercise in futility, as any such work is bound to be outdated by the time it is published.

Nevertheless, such compilations are immensely helpful for newcomers to the field, for established veterans with failing memories, for keeping track of recent updates, and for organizing future work. Indeed, a well-done classification becomes the framework for a diversity of fields and projects well beyond the systematic field.

The cut-off date for inclusion of taxa was set at 31 July 2009; we are however acutely aware that by the time this compilation sees the light of day, new taxa will have been described, some taxa will perhaps have been synonymised, and new insights into decapods relationships will have appeared in print. As additional modern studies are conducted there will inevitably be reassignments and re-evaluations; however, the present list reflects our best judgment based upon our personal evaluation of the literature and an intimate knowledge of that group of animals with which we are all fascinated, the decapod crustaceans.
The authors also examined the question "How many species of Decapoda are there?". Here's an excerpt of their response.
Based on our current effort, we put the total number of extant species of Decapoda at 14,756 (in 2,725 genera), with Brachyura accounting for 6,835 species, i.e. 46%.

This implies that in the last 50 years, the number of described species has nearly doubled! However, we are of course still a long way from knowing the true global diversity of Decapoda.
There are some photos of representative decapods, and our Singapore species are well represented in the section on decapods from freshwater and terrestrial habitats!
A. Macrobrachium lar (J. C. Fabricius, 1798)(Palaemonidae), Indonesia, Sulawesi, Manado (image by P. K. L. Ng);
B. Potamalpheops amnicus Yeo & Ng, 1997 (Alpheidae), Singapore (image by D. C. J. Yeo);
C. Caridina temasek Ng & Choy, 1990 (Atyidae), Singapore (image by H. W. Choy);
D. Euastacus spinifer (Heller, 1865) (Parastacidae), Australia, New South Wales, Wilson River (image by S. Ahyong);
E. Irmengardia johnsoni Ng & Yang, 1985 (Gecarcinucidae), Singapore (image by H. H. Tan);
F. Parathelphusa reticulata Ng, 1990 (Gecarcinucidae), Singapore (image
by Kelvin K. P. Lim);
G. Epigrapsus notatus (Heller, 1865) (Gecarcinidae), Taiwan (image by P. K. L. Ng);
H. Discoplax gracilipes Ng & Guinot, 2001 (Gecarcinidae), Philippines, Bohol (image by P. K. L. Ng).

Read more about these fascinating creatures!

Supplement Series No. 21 (2009): 1–109
"A classification of living and fossil genera of decapod crustaceans"
By Sammy De Grave, N. Dean Pentcheff, Shane T. Ahyong, Tin-Yam Chan, Keith A. Crandall, Peter C. Dworschak, Darryl L. Felder, Rodney M. Feldmann, Charles H. J. M. Fransen, Laura Y. D. Goulding, Rafael Lemaitre, Martyn E. Y. Low, Joel W. Martin, Peter K. L. Ng, Carrie E. Schweitzer, S. H. Tan, Dale Tshudy & Regina Wetzer.

On the Raffles Museum of Biodiversity Research website, download the PDF.

Thanks to the alert on the Raffles Museum News.

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