18


Journal of Paleontology 92(1):14–25


Figure 4. SEM images of Form A from the lower Cambrian Xinli section, NIGP160437. (1) Dorsal view; (2) ventral view; (3) left lateral view; (4) enlargement of area in white triangle in (1); (5) enlargement of area in white rectangle in (3); (6) posterior view. ls-1–ls-3 = 1st to 3rd large spinose sclerite. (1–3) Scale bar = 500 μm; (4) scale bar = 187 μm; (5, 6) scale bar = 319 μm.


Measurements.—Specimen NIGP160437 is about 1.8 mm in length and 370 μm in diameter at midpart, with the first large spinose sclerite (ls-1) about 140 μm long.


Remarks.—The orientation of Form A follows the topology of Eokinorhynchus rarus. The large spinose sclerites of E. rarus are distributed mostly on the dorsal side, functioning as defense organs. When this topology is applied to Form A, we treat the side with the large spinose sclerites as the dorsal side. The spines of the large spinose sclerites of E. rarus are directed posteriorly;


thus, when this topology is applied to Form A, we treat the end bearing the smooth tube as the posterior end. Thesmooth tubehas adiameterofabout 522 μmatthe larger


end. It should be some small shelly fossil that mantled the worm trunk end during taphonomy. Such smooth tube with a multi- layeredwall is separately recovered in theXinli section (Fig. 2.12); it has a diameter of about 810 μm at its larger end. As to NIGP160433 (Fig. 2.12), we treat the end with larger diameter as the upper part. When this orientation is applied to the tubemantling FormA(NIGP160437), it is evident that the upper part of the tube


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