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The microstructure of integument of cephalothorax in the late Cretaceous lobster, Linuparus japonicus NAGAO is described on the basis of scanning electron microscope study of the well-preserved specim...en from the Middle Campanian of Hokkaido. The integument of cephalothorax is composed of three different layers such as picuticle, endocuticle, and membranous layer, in descending order (Fig. 3). Numerous elliptical and circular tubercles are densely distributed on the surface of epicuticle (Pl. 17, Figs. 1-2). Each tubercle, about 100 to 120μm in diameter, has a shallow hollow in a central part, which is connected with a cylinder-like pore in the endocuticle (Pl. 17, Fig. 3). Within a central pore of some tubercles projections of irregular crystals frequently occur (Pl. 17, Figs. 5-6). They might be a product of diagenetic replacement of exotic material, because such projections have not yet been found in the modern Decapoda (FUKUDA, in press). The endocuticle is thickest (about 80%) among the three layers of integument. It is characterized by multi-layered lamellae. Each lamella, about 10μm thick, is made up of numerous alternating thicker and thinner calcareous fibrils (Pl. 18, Figs. 1-2). These fibrils have a concentric structure, being arranged obliquely to each lamellar plane. Many small pore canals of about 1μm diameter with the same trend with the central pore are running through the endocuticle (Pl. 18, Figs. 3-4). Similar structural features of endocuticle have been recognized in the two Mesozoic lobsters, Eryma striclandi and Hoploparia longimana by NEVILLE and BERG (1971) and DALINGWATER (1977), and also in the late Pleistocene Brachyura, Nurusia japonica (Pl. 18, Figs. 5-6). The density of pore canals within the cephalothorax in the present species is much lower than that within the walking legs and the abdomen in H. longimana, studied by DALINGWATER (1977). Taking this fact and YANO's (1974) biochemical study of the integument in modern brachyurid species into account, it is suggested that the density of pore canals within the integument in the Decapoda is probably related to the tropism of animals in life.続きを見る
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