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Journal of Paleontology 92(1):33–39
Cambrian Chengjiang fauna from which the new specimens of Kutorgina were collected belong to the Yu’anshan Member (the Eoredlichia-Wudingaspis trilobite Zone) of upper Heilinpu Formation (Qiongzhusian stage). More detailed account of the localities and stratigraphy can be found in Zhang et al. (2007).
United States.—The silicified specimens of Nisusia sulcate come from the mid-Cambrian Marjum Limestone of western Utah (Rowell and Caruso, 1985). A drawn interpretation of KUMIP 163499 is illustrated here (Fig. 1.2).
Figure 1. Diagrammatic drawings of the shell valves of kutorginides. (1) Posterior view of shell valves of Kutorgina chengjiangensis, showing the wide notothyrial and delthyrial opening between the outer margins of the notothyrium and pseudodeltidium (based on ELI BK-064A); (2) posterior view of Nisusia sulcata (based on Rowell and Caruso, 1985, fig. 9.7, KUMIP 163499), showing two apertures of the apical opening and the notothyrial and delthyrial opening plugged with silicified cylindroid pedicle discussed in this paper. Ap = apical perforation; Chi = chilidium; Dv = dorsal valve; Ndo = notothyrial and delthyrial opening between the outer margins of the notothyrium and pseudodeltidium; Ps = pseudodeltidium; P = pedicle; Vv = ventral valve.
2009;Williams and Carlson, 2007; Zhang et al., 2007), and in this kutorginate, the pedicle emerged posteriorly from the notothyrial and delthyrial opening, rather than from the apical perforation (Fig. 1.2). As noted by, for example, Williams and Carlson (2007), pedicles emerging from the apical foramen (such as in Kutorgina chengjiangensis) and from the posterior gap between the valves (such as in Nisusia sulcata) cannot be homologous structures, indicating that the kutorginates had a dual system of attachment, but the detailed distributions and polarity of character transitions that are important for understanding the phylogeny are still far from clear. However, the apical foramen may represent an early larval type of attachment in the stem of the Brachiopoda as suggested by numerous previous authors (e.g., Holmer, 2001; Popov et al., 2007, 2010; Williams and Carlson, 2007; Holmer et al., 2009).
Materials and methods
The discussed and illustrated rhynchonelliform brachiopods are derived from localities in China, Canada, and the United States. The age range is fromthe early Cambrian to the LateOrdovician.
China.—More than 150 specimens of Kutorgina chengjiangensis have been collected by the work team from Northwest University,Xi’an, China. The early collected 60 specimens for the original study (Zhang et al., 2007) and the additional (over 90) specimens for the current study (Fig. 2) were collected at the sections exposed around the south of Erjie town. The early
Canada.—The illustrated attached specimens of Nisusia? burgessensis Walcott, 1924, discussed in the following, all come from the middle Cambrian Burgess Shale Lagerstätte in British Columbia, Canada (Fig. 3.4, 3.5). Many species of Nisusia are providedwith spines,which seemingly are lacking in the Burgess species; pending further taxonomic revision, the generic assig- nation is conditional. Detailed accounts of the brachiopod faunas, localities, and stratigraphy can be found in Topper et al. (2014, 2015). A single silicified specimen of Eichwaldia subtrigonalis with preserved pedicle (Fig. 3.1–3.3) comes from the Late Ordovician Ottawa Formation,Allumette Island, Quebec,Canada (see Wright, 1981, and references therein). Fossils were examined with a binocular Olympus zoom
stereo microscope and photographed with a Nikon camera mounted on a photomicrographic system, with different illuminations for particular views when high-contrast images are required. The other specimens were taken to the Department of Palaeobiology, Uppsala University, and photographed with a camera lucida mounted on a Leica photomicrographic system. The artistic reconstructions and sketchy drawings of kutorginides were made by Zhang Z and Liu X in Northwest University of Xi’an.
Repositories and institutional abbreviations.—All the materials of Kutorgina chengjiangensis from China are deposited in the Early Life Institute (ELI), Northwest University, Xi’an, China; the silicified specimens of Nisusia sulcate from the United States are housed in the Museum of Invertebrate Paleontology (KUMIP), Lawrence, Kansas. The material of Nisusia? burgessensis Walcott, 1924 is housed in the Royal Ontario Museum (ROM) in Toronto, Canada (ROM 61116), and the National Museum of Natural History, Smithsonian Institution (USNM) inWashington D.C., USA.
Redescription of attachment structures in Kutorgina chengjiangensis
The lamellose shell of Kutorgina chengjiangensis is strongly biconvex, and it appears to have an astrophic hinge and a pointed ventral valve, but due to the preservation as flattened molds, this is not as easy to discern (Fig. 2) as in those specimens derived from carbonate lithologies. The shell has a relatively large, pos- terior, widely triangular notothyrial and delthyrial opening, occupying somewhat more than half of the total width of the valve, and it is clearly not associated with any attachment struc- tures in some well-preserved specimens with preserved pedicles (Fig. 2.1, 2.2). The ventral interarea is apsacline, and it is
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