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Journal of Paleontology 92(1):33–39
Figure 3. (1–3) GSC 1145, silicified internal of mold of Eichwaldia subtrigonalis;(1) lateral view of shell (whitened with ammonium chloride), showing silicified cylindroid pedicle, with closely spaced transverse grooves and emerging from the umbonal perforation; (2) detail of pedicle and umbo in dorsal view; (3) oblique ventral view; (4, 5) ROM 61116, two specimens of Nisusia? burgessensis attached to the dorsal spines of Wiwaxia (Series 3, Stage 5) Cambrian Burgess Shale, indicating that the pedicle probably emerged posteriorly between the valves (Topper et al., 2014, 2015); (4) attached specimen with possible umbonal foramen lacking emerging pedicle marked by white arrow; (5) attached specimen with posterior commissure oriented parallel to the substrate.
some specimens, and it seems to be built up by series of reg- ularly spaced, pronounced, stacked tabular discs (0.6–1.0 mm apart) (Fig. 2.1–2.5). The discs clearly have a pronounced three- dimensional preservation and may have been partly miner- alized. A dark central lineation in some specimens suggests that it may have had a cavity running along its central axis (Zhang et al., 2007). The distal termination of the pedicle attaches onto the exoskeletons of other animals, notably trilobites’ exuvae (Fig. 2.5, 2.6) (Zhang et al., 2008; Zhang and Holmer, 2013).
Diversity of exceptionally preserved attachment structures in kutorginate and chileate brachiopods
Nisusia sulcata.—Rowell and Caruso (1985) described excep- tionally preserved silicified cylindroid protrusions emerging posteriorly from the notothyrial and delthyrial opening in 15 of 18 complete shells of Nisusia sulcata; the cylindroid has a maximum length of 6 mm and closely spaced transverse grooves (Fig. 1.2). The various interpretations of this structure were discussed in some detail by Williams and Carlson (2007, p. 2848–2849), who noted that there are many problems associated with the original description by Rowell and Caruso (1985), where the cylindroid is interpreted as representing fecal matter
rather than an exceptionally preserved pedicle. Most important, no other such large coprolites are known to be produced by any living or fossil brachiopods, and the minute amount of food consumed by living brachiopods (e.g., Peck et al., 1997) results at most in micrometer-sized fecal pellets (James et al., 1992). Moreover, as noted byWilliams and Carlson (2007, p. 2849), “It is unlikely that excreta could have retained a constant shape in such a high proportion of shells collected.” The main reason Rowell and Caruso (1985) rejected the pedicle nature of the cylindroid is the presence of the apical foramen, which was known to serve as a pedicle in comparable closely related strophomenate brachiopods, and they noted that “It is conceivable that the orthodox opinion is in error, but we find it difficult to ascribe any other role to the opening” (Rowell and Caruso, 1985, p. 1234). However, as first suggested by Popov (cited in Williams and Carlson, 2007, p. 2848), the apical foramen in Nisusia may now be interpreted as the trace of a larval attachment, and the cylindroid most likely represents an adult type of pedicle; this was also discussed by Zhang et al. (2007, p. 1399).
Nisusia? burgessensis.—Outside of the Chengjiang Lagerstätte, the only record of still-attached kutorginates is represented by Nisusia? burgessensis from the Burgess Shale. Topper et al.
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