Holmer et al.—Attachment strategies of Cambrian kutorginate brachiopods
35
Figure 2. The Burgess Shale-type preservation of the rhynchonelliform brachiopod Kutorgina chengjiangensis from the Chengjiang fauna of China, showing the laminar tabular pedicle just aligned with ventral valve. (1) ELI BK-064A, dorsoventrally compressed internal mold of shell valves with well-developed pedicle, noting the widely triangular posterior opening between the posterior margin of two valves; (2) posterior view of the counterpart of (1), ELI BK-064A; (3) ELI BK-038A, rephotographed specimen from Zhang et al. (2007, fig. 2a) , showing the displaced and conjoined shell valves with the ventral below, aligned with stout pedicle proximal; (4) interpretative drawing of (3); (5) ELI BK-066, a dorsoventrally crushed specimen showing posterior view of shell valves with wide notothyrium and delthyrium, rephotographed specimen from Zhang et al. (2008, fig. 6h); (6) interpretative drawing of (5). Chi = chilidium; Dv = dorsal valve; Ex-T = exoskeletons of trilobite; Ndo = notothyrial and delthyrial opening between the outer margins of the notothyrium and pseudodeltidium; Ps = pseudodeltidium; P = pedicle; Vv = ventral valve.
provided with a rather broadly convex pseudodeltidium that clearly separates the protruding apical pedicle from the large and empty notothyrial and delthyrial opening (Fig. 2.3, 2.4). The dorsal interarea has minute chilidium and dorsal hinge furrows well imprinted on the inner side of the interarea (Fig. 2.5, 2.6). In life, the relatively large posterior notothyrial and delthyrial opening of Kutorgina chengjiangensis would have accom- modated the passage of the diductor muscle (see e.g., Rowell and Caruso, 1985, fig. 7; Bassett et al., 2001, fig. 18.2), andmust have been closed by the posterior body wall, perhaps also protected by a flexible organic integument. Atotal of 35 specimens of Kutorgina chengjiangensis have a preserved stout and annulated pedicle, and due to the flattened
compressed molded preservation of the shells, it was previously described as protruding between the delthyrium and notothy- rium of the shell valves (Zhang et al., 2007, p. 1396); however, reexamination of existing specimens and newly collected better- preserved material clearly shows that the pedicle is separated from the posterior opening, is subtended between delthyrium and notothyrium, and emerges from the apical perforation, but the exact size and shape of the apical perforation is obscured by the emerging pedicle (Fig. 2.1–2.6). However, the foramen is clearly much smaller compared with the emerging pedicle; thus, the ventral apex is largely encased by the proximal part of the pedicle. The pedicle is remarkably thick, up to 3.1 mm in diameter, occupying up to 30%–40% the total valve width in
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