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Journal of Paleontology 92(1):3–13
Figure 5. Peridermal tube of Olivooides multisulcatus from the Cambrian Kuanchuanpu Formation in South China. (1) Specimen ELISN19-20, aboral view showing five longitudinal rows of plicate corners (pc); (2–4) XX30-127. Oral view of the specimen. (2) Tube aperture with five plicate lobes (pl); (3) close-up of (2). (4) Diagnostic stellate ornament of the aboral ends. PR = perradii; IR = interradii.
ELISN148-52 were acquired at the Tohoku University (Fig. 2) and were processed using VG Studio 2.2 Max for 3D recon- structions. The terminology used herein mostly follows that of Conway Morris and Chen (1992), Van Iten (1992a), and Han et al., 2016a.
Repository and institutional abbreviation.—The figured speci- mens in this study are housed in the Early Life Institute (ELI), Northwest University, Xi’an, China.
Results
Figure 4. 3D reconstructions of Cambrian carinachitids with a hypothetical apical tip. (1–3) Lateral, oblique, and oral views, respectively, of Emeiconularia;(4–6) lateral, oblique, and oral views, respectively, of Carinachites spinatus;(7–9) lateral, oblique, and oral views, respectively, of Pentaconularia.
specimen of Carinachites spinatus that preserves the tube aperture. This specimen provides critical new insights into the morphology, systematic classification, and paleoautecology of carinachitids.
Materials and methods
Specimens of Carinachites spinatus were obtained from samples of phosphatic limestone collected from the Kuan- chuanpu Formation in southern Shaanxi Province, South China, and digested in 10% acetic acid. Specimens ELISN148-52, ELISN93-45, ELISN93-157, ELISN19-20, ELISN23-240, and ELISN12-154 come from the Shizhonggou section in Ningqiang County, while specimen XX30-127 is from the Yangjiagou section in Xixiang County (for localities, see Steiner et al., 2007, fig.1). All specimens were coated with gold and then imaged using an FEI Quanta 400 FEG scanning electron microscope (SEM). Micro-CT data for specimen
Tube morphology of Carinachites spinatus.—Carinachitids are abundantly represented by tetramerous C. spinatus Qian 1977 in the Kuanchuanpu Formation in the Shizhonggou section in Shaanxi Province. The tube of this species exhibits four prominent, equidimensional convex faces separated from each other by deep corner sulci (Figs. 1.3–1.6, 2.6). Each face usually bears a longitudinal series of arcuate transverse ribs that range in shape from simple welts to more complex folds (Conway Morris and Chen, 1992). The distance between adjacent ribs increases slightly toward the wide or oral end of the tube (Fig. 1.3). Near the facial midline, the region between any two adjacent ribs exhibits several, mutually parallel or irregular, longitudinal striated folds that in most cases are separated from each other by an inconspicuous shallow groove (Fig. 1.4). The transverse ribs in some specimens are arcuate near the
distal end and as wide as the faces (Fig. 1.3, 1.4), while in other specimens the ribs consist of a prominent, sharp, thorn-like spine (ts) such as those exhibited by specimens ELISN93-45 (Fig. 1.5) and ELISN148-52 (Fig. 1.6). The ribs on any two neighboring faces usually are located at the same levels above the apex, but some ribs exhibit longitudinal offset (Fig. 1.3, 1.4) (Conway Morris and Chen, 1992). In addition, the ribs of some specimens are offset along the facial midline (Conway Morris and Chen, 1992, fig. 6.1).
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