Taxonomy from Hu et al. 2017.
Revised diagnosis from Hu et al. 2017, p. 3: "Prosoma gently vaulted, semi-circular in outline, wider than long, lateral sides parallel, distally continuous into two genal angles. Cardiac lobe about 3/5 width of prosoma, tapering gradually forward. Ophthalmic ridges distinct, not meeting in front of the cardiac lobe. Eyes are low. Genal spines triangular, posteriorly directed, forming an acute angle with anterolateral margin of opisthosoma. Opisthosoma subtriangular, non-segmented, slightly wider than cardiac lobe, tapering backward gradually. Hinge relatively straight. Axial region in opisthosoma distinct, with a width 1/3 that of the opisthosoma. Six pairs of movable spines present on both sides of opisthosoma. Telson long and sword-like in outline, triangular in cross-section, with length equal to the body."
References:
Zhang, Q. Y., Hu, S. X., Zhou, C. Y., Lv, T. & Bai, J. K. (2009) New occurrence of Xiphosura in China. Prog. Nat. Sci. 19, 1090–1093 (2009).
Hu, S. X., Zhang, Q. Y., Feldmann, Rodney, Benton, Michael J., Schweitzer, Carrie E., Huang, J. Y., Wen W., Zhou, C. Y., Xie, T., Lü, T., & Hong, S. G. (2017) Exceptional appendage and softtissue preservation in a Middle Triassic horseshoe crab from SW China. Scientific Reports | 7: 14112 | DOI:10.1038/s41598-017-13319-x.