New Jurassic spinicaudatans from Xinjiang Uygur Autonomous Region of northwestern China and their evolutionary implications

New Jurassic clam shrimps have been discovered respectively from the Hettangian lower part of the Badaowan Formation in the Junggar Basin, and the Oxfordian upper part of the Qiketai Formation in the Turpan Basin of Xinjiang, northwestern China. Through the examination under a scanning electron microscope (SEM) of well-preserved specimens we have described a new genus Punctatestheria n. gen., which includes two new species Punctatestheria lianmuqinensis n. gen. n. sp. and Punctatestheria karamayensis n. gen. n. sp. Given their similar punctate carapace ornamentation pattern, the British Bajocian-Bathonian species Euestheria trotternishensis is herein attributed to the new genus. Punctatestheria n. gen. first occurred in the Hettangian and ranged into the Oxfordian. This finding supports the previous hypothesis that punctatestheriids have first derived from the Triassic lineage Aquilonoglypta, and then gave rise to triglyptids in the Bathonian, because in Triglypta three kinds of ornaments have ontogenetically developed on the carapace, the juvenile-stage dorsal part of which is ornamented by evenly distributed puncta.