Yanbin Shen

Flusskrebs Spermatophoren

■at 61 Recent crayfish I'rocanibarus clarkii. Dorsal view of a male (Left). Ventral view of a male, showing the tubular form of pleopods 1 and 2 (Middle), ventral view of female, showing the annulus ventralis and pleopods 1—5 (Righfi. (Photo: Shi-wei Zhao/ NIGP)

The highly sporadic fossil record of" freshwater shrimps is improved by the discovery of abundant specimens ol astacids and spelaeogriphids from thcjchol Group. The former are a large well-known crayfish (Decapoda, Astacidea) and the tatter a new member of the family Spelaeogriphidae (Hemicaridea), Liaoningogriphus.

Crayfish Astacids are commonly referred to as "crayfish", anil are also known by many other common names in the different parts of the world: crawfish, paper-shell crabs, ecrevisse, yabbics, mud-bugs, flusskrebs. raks, ditch bugs anil koonacs. With over 500 known species, they are almost distributed worldwide.

Traditionally, two large groups of freshwater crayfish are recognized, the superfamilies Astacoidea and Parastacoidea. The astacoids live in the Northern Hemisphere. They are divided into the family Astacidae (Europe, western North America) and the family Cambaridae (North America and East Asia). The parastacoids arc restricted ro the Southern Hemisphere.

The Astacidea is characterized by subcylindrical céphalothorax, well-developed rostrum and abdomen, simple cervical groove, chelate first three pcrciopods with the first of them the largest, well-developed abdominal pleura, telson with transverse suture, and uropods with diaeresis.

Males of the superfamily Astacoidea are typically with the first and second pleopods modified into a rather elongated, styLiform blade to assist in the transfer of the spermatophore. Females of the family Cambaridae bear an

■at 61 Recent crayfish I'rocanibarus clarkii. Dorsal view of a male (Left). Ventral view of a male, showing the tubular form of pleopods 1 and 2 (Middle), ventral view of female, showing the annulus ventralis and pleopods 1—5 (Righfi. (Photo: Shi-wei Zhao/ NIGP)

62 A mnle Cricoidoscelosus aetlws in ventral view, 87 mm long from rostrum to distal telson, from Dawangzhangzi locality (Yixian Formation) in Linyuan, Liaotting. (Photo: Da-jian Li/ CAS)

62 A mnle Cricoidoscelosus aetlws in ventral view, 87 mm long from rostrum to distal telson, from Dawangzhangzi locality (Yixian Formation) in Linyuan, Liaotting. (Photo: Da-jian Li/ CAS)

»63 A female Cricoidoscelosus aethus in lateral view. 99 mm long from top of cheliped to the last pleomere. from Dawangzhangzi locality (Yixian Formation) in l.inyuan, Liaoning. (Photo: Da-jian Li/CAS)

64 Tail fan in ventral view (27 mm wide) of a female Cricoidoscelosus act bus, from Dawangzhangzi locality (Yixian Formation) in l.inyuan, Liaoning. (Photo: Dong-xing Deng,' N1CP)

tt/i65 A molted crayfish exoskeleton 1115 mm long) of a female Cricoidoscelosus aetlws, from Dawangzhangzi locality (Yixian Formation) in Linyuan, Liaoning. (Photo: Da-jian Li/ CAS)

»63 A female Cricoidoscelosus aethus in lateral view. 99 mm long from top of cheliped to the last pleomere. from Dawangzhangzi locality (Yixian Formation) in l.inyuan, Liaoning. (Photo: Da-jian Li/CAS)

64 Tail fan in ventral view (27 mm wide) of a female Cricoidoscelosus act bus, from Dawangzhangzi locality (Yixian Formation) in l.inyuan, Liaoning. (Photo: Dong-xing Deng,' N1CP)

tt/i65 A molted crayfish exoskeleton 1115 mm long) of a female Cricoidoscelosus aetlws, from Dawangzhangzi locality (Yixian Formation) in Linyuan, Liaoning. (Photo: Da-jian Li/ CAS)

annulus ventralis, a specific form of spermatheca, in the areas between the fourth and fifth pereiopods (Fig. 61). The males of the Cambaridae sometimes have a robust set of directed processes, or ischial hooks, on the second through fourth pereiopods. However, the members of the Astacidae lack ischial hooks in the males and annulus ventralis structure in the females.

The crayfish specimens of the Jehol Biota were obtained from the Yixian Formation in Dawangzhangzi, Daxinfangzi, Songzhangzi, and Niuyingzi areas, Lingyuan City, and Houshuangshanzi village of Yixian County, Jinzhou City, Liaoning Province. The excellently preserved specimens include molted exoskeleton, juveniles, adults, males and females, as well as dorsal, ventral and lateral remains of the thorax. They were named as Cricoidoscelosus aethus (Figs. 62—65) and Palaeocambarus licenti by Taylor, Schram and Shen (Family Cricoidoscelosidae) (Figs. 66, 67). The former is distinguished from the latter in its flagellate or crenulate pleopods, whereas the latter bears paddle pleopods. Both of them are very similar to recent cambarideans in their modified first pleopod in the males and annulus ventralis in the females.

Living crayfish mostly inhabits freshwater habitats. Some species can tolerate high salinity, e.g., in the Caspian Sea and Black Sea, but they were never found in real marine environments. More than 500 species of freshwater crayfish are found in the temperate zones of the Northern Hemisphere, and the temperate and tropical zones of the Southern Hemisphere.

Crayfish is polygraphist and feeds on a variety of living and dead animal and plant materials. A few species of the family Astacidae are also adapted to the cold-water habitats. Typically, molting is restricted to the warmer summer months, when feeding can take place. In contrast, the members of the family Cambaridae show greater variations and reflect their ability to adapt to a wider range of habitats than the Astacidae. A number of species of the Cambaridae have the ability to make burrows or burrow systems, which enable them to inhabit water bodies that are periodically dried out. Other species occur in both lotic and lentic habitats under rocks, in vegetation, among the roots of riparian trees, in leaf litter and they also burrow into the gravel beds of streams.

Liaoningogriphus The family Spelaeogriphidae possesses a typically peracaridan brood pouch with five pairs of oostegites, and was thus placed within the Superorder Peracarida (Order Hemicaridea). The living Spelaeogriphus was first found from underground cave pools in the Table Mountain, South Africa. Acadicaris novoscotica, the only known fossil species, was reported from the Lower Carboniferous black shale in the Maritime Province of Canada. Recently, some other fossil spelaeogriphaceans from the Lower Cretaceous

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