Fig. 16

Limulus polyphemus and Pentecopterus decorahensis, cuticular features of tergites. a Limulus polyphemus, cracking of the cuticular surface. b–q Pentecopterus decorahensis, mesosomal tergites. b SUI 140020, portion of tergite showing row of enlarged scales and cracking of the cuticle. c SUI 140044, sparse scale ornamentation and cracking of the surface. d SUI 140039, weathered portion of cuticle showing advanced stages of cracking. e SUI 140046, regular scale ornament. f SUI 139954, lateral portions of articulated tergites. g SUI 140038, anterior portion of tergite showing the articulating facet devoid of ornamentation. h SUI 140027, tergite showing row of enlarged scales and posterior doublure. i SUI 140042, smooth anterior articulating facet and central row of enlarged guttalate scales. j SUI 140043, scale ornament. k SUI 140057, lateral portion of tergite showing ancillary row of scales along margin. l SUI 140045, anterior articulating facet of tergite. m SUI 140026, widely spaced follicles. n SUI 140028, uniform scale ornament. o SUI 140021, showing faint cracking of the cuticle. p SUI 140022, merging of scales towards posterior of tergite and fragment of posterior doublure. q SUI 140025, broadening and merging of rounded scales towards rear of tergite. AF = articulating facet, CC = cuticular cracking, FO = follicles, PD = posterior doublure, SC = scales, SR = scale row. Scale bars = 10 mm