| 2 | Morphological variation in fossil crayfish of the Jehol biota,Liaoning Province,China and its texonomic discrimination显示文摘Twelve morphological characteristics in 61 fossil crayfish specimens, which came from the Upper Jurassic Yixian Formation, are discussed respectively in the present paper. A study of these new and better preserved materials allows us to add to and revise the original description for Family Cricoidoscelosidae. In our collection, no modifications of the second pleopod of the males have yet been noted. This would be a crucial factor for the diagnosis of the family. Based on the presence of annulus ventralis in both Cricoidoscelosus and Palaeocambarus, they would appear to be very closely allied to those characteristics of the Family Cambaridae. In regard to the family Protastacidae, we seriously doubt it is actually crayfish, in light of the lack of any apomorphies identifiable within the Astacida, and their marine habitat. | SHEN Yanbin, Frederick R. Schram & Rod S. Taylor Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences, Nanjing 210008, China Zoological Museum, University of Amsterdam, P. O. Box 94766, 1090 GT Amsterdam, The Netherlands Department of Earth Sciences, Cambridge University, Cambridge CB2 3EQ, United Kingdom | 2001 | Chinese Science Bulletin2001，46，1： | 6 |
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