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Journal of Paleontology 92(1):3–13
Figure 1. Carinachitids from the lower Cambrian Kuanchuanpu Formation in South China. (1) Triradiate Emeiconularia amplicanalis Liu et al., 2005. (2) Pentamerous Pentaconularia ningqiangensis Liu et al., 2011. (1, 2) Courtesy of Y.H. Liu. (3–6) Tetraradiate Carinachites spinatus Qian, 1977. (3, 4) ELISN93-157, showing the displacement between neighboring arcuate ribs, which are connected in the middle by striations. Both the faces and ribs widen slightly toward the apertural end of the skeleton. (5) ELISN93-45. (6–12) ELISN148-52. (6, 7) Lateral view of the tube. (8, 9) Close-up of the tube aperture shows one of the plicate apertural lobes being elevated above the others. (10) The elevated, plicate apertural lobes with converging striated folds. (11) Single plicate apertural lobe with converging striated folds and the corner sulci with parallel striations. (12) Close-up of (11) showing secondary cracks on the striated surface. IR = interradius; PR = perradius; cs = corner sulci; pal = plicate apertural lobes; st = striations; tr = transverse ribs; ts = thorn-like spines.
(see Steiner et al., 2014), have been assigned to the order Conulariida of the subclassConulata (He, 1987;Qian et al., 1999). Because carinachitids and hexangulaconulariids are very small (<5mm long) and lack the facial midline and carina typical of many Ordovician and younger conulariids, they have been classified as protoconulariids (Qian et al., 1999). The zoological affinities of Conulata have been controversial (Babcock et al.,
1986;Brood, 1995), but the group is nowgenerally assigned to the subphylum Medusozoa of the phylum Cnidaria (Bengtson and Yue, 1997; Van Iten et al., 2006, 2010, 2014). Phylogenetic relationships among protoconulariids remain poorly understood as all previously collected specimens of carinachitids lack both the apical and apertural regions, and thus their complete morphology and growth patterns are
unknown.Herewe describe a tetramerous
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