. Bulletin of the British Museum (Natural History). The stalk joints of recent Isocrinidae (Crinoidea) Michel Roux Laboratoire de Paleontologie, Universite de Paris-Sud, 91405, Orsay, France Contents Synopsis. ............ Introduction ............ Main morphological features of stalk joints Taxonomic significance of Isocrinid stalk joints Key to the recent genera of Isocrinidae based on the morphology of the symplexial stalk joints ........... Synostoses of the material studied Conclusions ........... Acknowledgements ........... References ....... 45 45 45 47 58 58 63 64 64 Synopsis The stal
. Bulletin of the British Museum (Natural History). The stalk joints of recent Isocrinidae (Crinoidea) Michel Roux Laboratoire de Paleontologie, Universite de Paris-Sud, 91405, Orsay, France Contents Synopsis. ............ Introduction ............ Main morphological features of stalk joints Taxonomic significance of Isocrinid stalk joints Key to the recent genera of Isocrinidae based on the morphology of the symplexial stalk joints ........... Synostoses of the material studied Conclusions ........... Acknowledgements ........... References ....... 45 45 45 47 58 58 63 64 64 Synopsis The stalk joints of recent genera representative of the crinoid family Isocrinidae have been observed with the scanning electron microscope. This study indicates that the detailed morphology of the symplexial and synostosial articulations has taxonomic significance. Neocrimis and Hypalociinus differ from the other genera by many characters. They have affinities with the fossil Balanocrinus group. Such a study is of interest for comparison between the fossil and recent taxa with respect to the variability of the external morphology of the stalk. Introduction Many fossil species of stalked crinoids have been described from dissociated parts of their columns, their calyces and arms being unknown. When a primarily fossil family includes recent representatives, it is very important for palaeontological studies to have detailed descriptions of the stalk joints of the modern species. With this in mind I have observed columnal facets of recent Isocrinidae under the scanning electron microscope. An earlier study (Roux, 1974) suggested that the microstructural organization of the pentalobate stalk joints has taxonomic significance. To confirm this possibility, 1 have selected mature columnals of all the recent genera and of four species of the genus Metacrinus. The following Isocrinidae are described: Metacrinus nobilis Carpenter Diplocrinus alterniciirus (Carpenter) M. rotundtis Carpenter Annac
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