A new genus of clam shrimp from the Upper Triassic Anyuan Formation of Jiangxi, China

The clam shrimp Xiangxiellinae (Spinicaudata), characterized by one or two short ribs on the large larval valve, is comprised of two genera: Xiangxiella Shen, 1976 and Protomonocarina Tasch, 1962. The members of this subfamily are widely distributed in the Upper Carboniferous to the Triassic strata in the world. The new genus Dicerestheria gen. nov. is established based upon specimens from the Upper Triassic Xufang Member of the Anyuan Formation in Wuzhou City, Jiangxi Province. Its large larval valve bears two bifurcate, short, and stout ribs. It is very similar to Xiangxiella in that they both have two ribs on the larval valve, but the ribs of the new genus are much stronger than those of the latter. The growth bands of the new genus are ornamented with medium reticulate sculpture. It is speculated that the larval valve ribs might be caused by variation of attachments of the adductor muscles, or by changes of their habitat and living environments. The Anyuan Formation consists of a set of coal-measure sediments, yielding brackish bivalves and abundant Norian plants represented by the Ptiozamites-Anthrophyopsis flora, reflecting an environment in humid tropical-subtropical climate. Therefore, the new genus may have lived adjacent to nearshore marsh environments in warm and humid tropical-subtropical climate.

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