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A map of southern Shaanxi Province showing the localities from which samples have been studied. Modified from Steiner et al., 2004.
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Cambrothyra ampulliformis Qian and Zhang, 1983, is a jar- or vase-shaped fossil known from the Lower Cambrian of Shaanxi and Hubei provinces, China. It has been interpreted as a protistan test or cyst or a metazoan sclerite. A large collection of specimens from the Xihaoping Member of the Dengying Formation in southern Shaanxi Province permits its...
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... we describe material of Cambrothyra from the Xihaoping Member of the Dengying Formation, Xiaowan and Yangjiagou (5Sanlangpu) sections, Xixiang County, Shaanxi Province ( Fig. 1; ). The Xihaoping Member is a phosphatic limestone that unconformably overlies Ediacaran dolostones of the Beiwan Member of the Dengying Formation. Its thickness is highly variable and ranges in Shaanxi Province from a few centimeters to ca. 8.5 m ( Qian et al., 1999, fig. 3-13; ); at Xiaowan the Xihaoping Member is ca. 45 cm thick and ...
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... and Yangjiagou (5Sanlangpu) sections, Xixiang County, Shaanxi Province ( Fig. 1; ). The Xihaoping Member is a phosphatic limestone that unconformably overlies Ediacaran dolostones of the Beiwan Member of the Dengying Formation. Its thickness is highly variable and ranges in Shaanxi Province from a few centimeters to ca. 8.5 m ( Qian et al., 1999, fig. 3-13; ); at Xiaowan the Xihaoping Member is ca. 45 cm thick and at Yangjiagou it is ca. 5 cm thick ( ). It is overlain by silty shales of the Guojiaba Formation. The Xihaoping Member is interpreted to have been deposited in a high-energy, peritidal environment ( ), along the northern margin of the Yangtze ...
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... Cambrothyra material is also illustrated from the Meishucunian (Nemakit-Daldynian) Kuanchuanpu Forma- tion from the Shizhonggou section, near Kuanchuanpu, Ningqiang County, Shaanxi Province ( Fig. 1; detailed strati- graphic information is presented in ...
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... is never seen elsewhere on the sclerite. Occasionally these verruculae are preserved as a thin phosphatic crust with their interiors having been dissolved ( Fig. 6.5-6.7). Other forms of ornament are less common. Occasionally ruffles or crenulations are borne on the ''neck'' (Figs. 5.8, 7.2, 7.4, 7.5) or on the ridge around the basal facet ( Fig. 6.14; see also Duan et al., 1993, pl. 2, fig. 23); sometimes the former are marked enough to divide the ''neck'' into a series of knob-like protuberances ( Fig. 6.4; see also Duan et al., 1993, pl. 1, fig. 23). The sides of the sclerites are generally smooth, but occasionally bear distally inclined scale-like projections 20-50 mm in length ...
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... ( Fig. 6.4; see also Duan et al., 1993, pl. 1, fig. 23). The sides of the sclerites are generally smooth, but occasionally bear distally inclined scale-like projections 20-50 mm in length (Figs. 4.9, 5.1, 5.2, 5.14, 5.18, 6.10, 6.12-6.15, 10.2, 10.4); sometimes these are represented by holes through the outer phosphatic coating of the sclerite (Fig. 6.12, 6.13, 6.15) with the projections themselves never having become phosphatized and consequently dissolving during acid ...
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... molds commonly bear numerous spine-like exten- sions 4-8 mm in diameter ( Figs. 7.1-7.4, 7.6-7.12, 8.1, 8.4-8.6, 8.9-8.12). These occur over the entire surface of the sclerite except for the basal facet ( Fig. 7.1, 7.10, 7.12); one specimen may preserve these structures on the basal facet ( Fig. 8.4), but it cannot be interpreted with certainty. Some specimens preserve both a mold of the interior and a partial coating of the outer wall of the sclerite; where the outer coating has broken away these spines can be seen to extend like pillars across ...
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... few internal molds of sclerites preserve patches of a microstructure consisting of fibers ca. 1 mm wide oriented approximately radially away from the foramen (Fig. 8.1-8.3, 8.5-8.8, 8.12). Similar microstructures have been interpreted as phosphatized fibers of aragonite in both coeloscleritophor- ans ( Bengtson et al., 1990;Mehl, 1996;Porter, 2004Porter, , 2008Vinther, 2009; see Fig. 11.4, 11.5, 11.8) and other Cambrian fossils (Runnegar, 1985a, b;Kouchinsky, 2000a, b;Kouchinsky and Bengtson, 2002;Feng ...
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... patches of a microstructure consisting of fibers ca. 1 mm wide oriented approximately radially away from the foramen (Fig. 8.1-8.3, 8.5-8.8, 8.12). Similar microstructures have been interpreted as phosphatized fibers of aragonite in both coeloscleritophor- ans ( Bengtson et al., 1990;Mehl, 1996;Porter, 2004Porter, , 2008Vinther, 2009; see Fig. 11.4, 11.5, 11.8) and other Cambrian fossils (Runnegar, 1985a, b;Kouchinsky, 2000a, b;Kouchinsky and Bengtson, 2002;Feng and Sun, 2003), suggesting that Cambrothyra sclerites were also originally aragonitic. On a few internal molds, larger cylindrical structures, 4-8 mm in diameter, are preserved on the basal facet ( Fig. 8.6, 8.8-8.11); ...
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... NIGP 152141 (same specimen as Figure 6.3); 17, NIGP 152134; 18, NIGP 152146. Specimens are from the Xiaowan section (1-3, 6, 10, 13, 14: sample SXX-08-06; 4, 7, 8, 12, 15-18: sample Xiw 103) and the Yangjiagou section (5, 9, 11: sample Slp 1). All scale bars are 100 mm. Clausen, 2010). In one specimen a microboring curves to avoid the pores (Fig. 8.11). In some cases, traces of the fibrous microstructure are preserved on the walls of the microborings (Fig. ...
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... section (1-3, 6, 10, 13, 14: sample SXX-08-06; 4, 7, 8, 12, 15-18: sample Xiw 103) and the Yangjiagou section (5, 9, 11: sample Slp 1). All scale bars are 100 mm. Clausen, 2010). In one specimen a microboring curves to avoid the pores (Fig. 8.11). In some cases, traces of the fibrous microstructure are preserved on the walls of the microborings (Fig. ...
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... most sclerites are preserved singly, sometimes multiple sclerites are attached to each other in pairs ( Fig. 9.1-9.5; see also Geng and Zhang, 1987, pl. 1, fig. 7; Ding et al., 1990, pl. 2, fig. 37; Duan et al., 1993, pl. 2, figs. 10, 11, 19, 20;Cao, 1996, pl. 2, fig. 15; Qian et al., 2000, pl. 1, fig. 5) or in small clusters of a few sclerites ( Fig. 9.6-9.9; see also Qian et al., 2000, pl. 1, figs. 1, 2, 7; Cao, 2000, pl. 1, fig. 19; fig. 11.6). ...
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... most sclerites are preserved singly, sometimes multiple sclerites are attached to each other in pairs ( Fig. 9.1-9.5; see also Geng and Zhang, 1987, pl. 1, fig. 7; Ding et al., 1990, pl. 2, fig. 37; Duan et al., 1993, pl. 2, figs. 10, 11, 19, 20;Cao, 1996, pl. 2, fig. 15; Qian et al., 2000, pl. 1, fig. 5) or in small clusters of a few sclerites ( Fig. 9.6-9.9; see also Qian et al., 2000, pl. 1, figs. 1, 2, 7; Cao, 2000, pl. 1, fig. 19; fig. 11.6). Each sclerite bears a distinct foramen and the foramina of all sclerites in a cluster open in the same direction. As previously argued by Qian et al. (2000), ...
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... each other in pairs ( Fig. 9.1-9.5; see also Geng and Zhang, 1987, pl. 1, fig. 7; Ding et al., 1990, pl. 2, fig. 37; Duan et al., 1993, pl. 2, figs. 10, 11, 19, 20;Cao, 1996, pl. 2, fig. 15; Qian et al., 2000, pl. 1, fig. 5) or in small clusters of a few sclerites ( Fig. 9.6-9.9; see also Qian et al., 2000, pl. 1, figs. 1, 2, 7; Cao, 2000, pl. 1, fig. 19; fig. 11.6). Each sclerite bears a distinct foramen and the foramina of all sclerites in a cluster open in the same direction. As previously argued by Qian et al. (2000), these do not appear to be chance associations; besides the common orientation of the foramina, the different sclerites usually have flattened facets where they ...
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... in pairs ( Fig. 9.1-9.5; see also Geng and Zhang, 1987, pl. 1, fig. 7; Ding et al., 1990, pl. 2, fig. 37; Duan et al., 1993, pl. 2, figs. 10, 11, 19, 20;Cao, 1996, pl. 2, fig. 15; Qian et al., 2000, pl. 1, fig. 5) or in small clusters of a few sclerites ( Fig. 9.6-9.9; see also Qian et al., 2000, pl. 1, figs. 1, 2, 7; Cao, 2000, pl. 1, fig. 19; fig. 11.6). Each sclerite bears a distinct foramen and the foramina of all sclerites in a cluster open in the same direction. As previously argued by Qian et al. (2000), these do not appear to be chance associations; besides the common orientation of the foramina, the different sclerites usually have flattened facets where they articulate with ...
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... their sclerites as indicated by flattened sides on the periphery of the cluster (Fig. 9.7), further supporting this idea. Sclerites in these pairs and clusters resemble isolated sclerites in their morphological variability. Different sclerites within a single cluster may differ in size ( Fig. 9.3-9.6, 9.9), shape ( Fig. 9.4, 9.5), cross-section ( Fig. 9.1, 9.7), and shape of the foramen (Fig. 9.4, ...
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... addition to these pairs and clusters of distinct sclerites, twin sclerites, in which two sclerites with distinct distal ends share a common foramen and basal facet, are commonly found ( Fig. 10.1-10.11; see also Duan et al., 1993, pl. 2, figs. 11, 21;Cao, 1996, pl. 2, fig. 14). In these twin sclerites, there is generally a groove running up one (Fig. 10.1, 10.7) or both ( Fig. 10.6, 10.10) sides of the sclerite, separating the two parts of the sclerite. Occasional specimens of sclerites with a single distal end have a groove cutting ...
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... addition to these pairs and clusters of distinct sclerites, twin sclerites, in which two sclerites with distinct distal ends share a common foramen and basal facet, are commonly found ( Fig. 10.1-10.11; see also Duan et al., 1993, pl. 2, figs. 11, 21;Cao, 1996, pl. 2, fig. 14). In these twin sclerites, there is generally a groove running up one (Fig. 10.1, 10.7) or both ( Fig. 10.6, 10.10) sides of the sclerite, separating the two parts of the sclerite. Occasional specimens of sclerites with a single distal end have a groove cutting across the edge of the basal facet ( Fig. 10.12-10.15); these perhaps ...
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... addition to these pairs and clusters of distinct sclerites, twin sclerites, in which two sclerites with distinct distal ends share a common foramen and basal facet, are commonly found ( Fig. 10.1-10.11; see also Duan et al., 1993, pl. 2, figs. 11, 21;Cao, 1996, pl. 2, fig. 14). In these twin sclerites, there is generally a groove running up one (Fig. 10.1, 10.7) or both ( Fig. 10.6, 10.10) sides of the sclerite, separating the two parts of the sclerite. Occasional specimens of sclerites with a single distal end have a groove cutting across the edge of the basal facet ( Fig. 10.12-10.15); these perhaps reflect a similar ...
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... clusters of distinct sclerites, twin sclerites, in which two sclerites with distinct distal ends share a common foramen and basal facet, are commonly found ( Fig. 10.1-10.11; see also Duan et al., 1993, pl. 2, figs. 11, 21;Cao, 1996, pl. 2, fig. 14). In these twin sclerites, there is generally a groove running up one (Fig. 10.1, 10.7) or both ( Fig. 10.6, 10.10) sides of the sclerite, separating the two parts of the sclerite. Occasional specimens of sclerites with a single distal end have a groove cutting across the edge of the basal facet ( Fig. 10.12-10.15); these perhaps reflect a similar ...
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... pl. 2, figs. 11, 21;Cao, 1996, pl. 2, fig. 14). In these twin sclerites, there is generally a groove running up one (Fig. 10.1, 10.7) or both ( Fig. 10.6, 10.10) sides of the sclerite, separating the two parts of the sclerite. Occasional specimens of sclerites with a single distal end have a groove cutting across the edge of the basal facet ( Fig. 10.12-10.15); these perhaps reflect a similar ...
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... few clusters of sclerites that are flattened parallel to the basal facet or are otherwise highly irregular have been identified in the same samples that have yielded Cambrothyra (Fig. 9.10-9.13); some have a verruculose texture on their presumed basal facets ( Fig. 9.12, 9.13). Similar material has been assigned to Cambrothyra by Qian et al. (2000, pl . 1, fig. 4), but the origin of these clusters is unclear as they do not closely resemble isolated Cambrothyra sclerites, nor can they be assigned to other known ...
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... few clusters of sclerites that are flattened parallel to the basal facet or are otherwise highly irregular have been identified in the same samples that have yielded Cambrothyra (Fig. 9.10-9.13); some have a verruculose texture on their presumed basal facets ( Fig. 9.12, 9.13). Similar material has been assigned to Cambrothyra by Qian et al. (2000, pl . 1, fig. 4), but the origin of these clusters is unclear as they do not closely resemble isolated Cambrothyra sclerites, nor can they be assigned to other known ...
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... of sclerites that are flattened parallel to the basal facet or are otherwise highly irregular have been identified in the same samples that have yielded Cambrothyra (Fig. 9.10-9.13); some have a verruculose texture on their presumed basal facets ( Fig. 9.12, 9.13). Similar material has been assigned to Cambrothyra by Qian et al. (2000, pl . 1, fig. 4), but the origin of these clusters is unclear as they do not closely resemble isolated Cambrothyra sclerites, nor can they be assigned to other known ...
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... agree with Qian et al. (2000) that continuous variation connects previously described species, but we further argue that the distinction between Cambrothyra ampulliformis and C. truncata is similarly blurred by intermediate forms. Variability in the basal facet, such that some sclerites have a long ''neck'' ( Fig. 5.1, 5.2, 5.7-5.9), some have an extremely short ''neck'' (Fig. 5.3, 5.15), and others entirely lack a ''neck'' ( Fig. 5.4, 5.5, 5.10, 5.16), renders these groups intergradation- al. In addition, other sclerites do not easily fall into either category, such as those in which the basal facet is reduced to a narrow ring (Fig. 5.13, 5.14. ...
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... have a long ''neck'' ( Fig. 5.1, 5.2, 5.7-5.9), some have an extremely short ''neck'' (Fig. 5.3, 5.15), and others entirely lack a ''neck'' ( Fig. 5.4, 5.5, 5.10, 5.16), renders these groups intergradation- al. In addition, other sclerites do not easily fall into either category, such as those in which the basal facet is reduced to a narrow ring (Fig. 5.13, 5.14. 5.18) or those in which the surface of the basal facet extends proximally as a ''neck'' but in which a ridge runs around the outer edge of the basal facet so that the rim of the foramen is below the outer rim of the basal facet (Fig. 5.11, 5.17; a similar sclerite was placed in C. truncata by Qian et al. [2000, pl. 1, fig. 6]). ...
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... easily fall into either category, such as those in which the basal facet is reduced to a narrow ring (Fig. 5.13, 5.14. 5.18) or those in which the surface of the basal facet extends proximally as a ''neck'' but in which a ridge runs around the outer edge of the basal facet so that the rim of the foramen is below the outer rim of the basal facet (Fig. 5.11, 5.17; a similar sclerite was placed in C. truncata by Qian et al. [2000, pl. 1, fig. 6]). A similar range of morphologies is shown in the illustrations of Duan (1986), , and Qian et al. (2000). The different individual sclerites within pairs or clusters of sclerites, which certainly originally came from a single animal, generally have ...
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... sclerites within the same pair or cluster often show differences in outline, cross- section, shape of the foramen, and angle between the basal facet and long axis (although the full range of variation among sclerites is never expressed within a single pair or cluster), demonstrating that a single Cambrothyra animal had variable sclerites ( Fig. 9.1-9.9; see also Qian et al., 2000). Consequent- ly, we attribute all of this material to a single, highly variable ...
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... microstructural characters (Bengtson, 2005;Porter, 2008): the sclerite wall has an outer organic layer and an inner layer of longitudinally oriented aragonite fibers; the upper surface of the sclerite of many coeloscleritophorans bears projections, while the lower surface is smooth. Scale-like projections are present in some Cambrothyra sclerites (Figs. 6.12-6.15, 10.2, 10.4), although they do not seem to be restricted to one particular side of the sclerite and appear to be absent from most sclerites. The wall of Cambrothyra sclerites was likely composed of fibrous aragonite (Fig. 8.1- 8.3, 8.5-8.8, 8.11). The frequent phosphatization of the outer surface of the sclerite may suggest that an outer organic ...
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... projections, while the lower surface is smooth. Scale-like projections are present in some Cambrothyra sclerites (Figs. 6.12-6.15, 10.2, 10.4), although they do not seem to be restricted to one particular side of the sclerite and appear to be absent from most sclerites. The wall of Cambrothyra sclerites was likely composed of fibrous aragonite (Fig. 8.1- 8.3, 8.5-8.8, 8.11). The frequent phosphatization of the outer surface of the sclerite may suggest that an outer organic layer was present, as the decay of organic matter greatly aids in the process of phosphatization ( Lucas and Prévô t, 1991). The occasional preservation of scale-like projections as holes through an outer phosphatic ...
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... 8.1- 8.3, 8.5-8.8, 8.11). The frequent phosphatization of the outer surface of the sclerite may suggest that an outer organic layer was present, as the decay of organic matter greatly aids in the process of phosphatization ( Lucas and Prévô t, 1991). The occasional preservation of scale-like projections as holes through an outer phosphatic layer (Fig. 6.12, 6.13, 6.15) closely resembles the situation in other coeloscleritophorans where the outer phosphatic coat is interpreted as an organic layer that did not get phosphatized where it covered calcareous projections (Porter, 2004(Porter, , 2008. None of these microstructural characters are unique to coeloscleritophorans, so their presence in ...
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... other coeloscleritophorans further resemble Cam- brothyra in possessing pores that penetrate the sclerite wall. Possible pores in chancelloriid sclerites have occasionally been noted in the literature ( Bengtson et al., 1990, fig. 23G, 23H; Wrona, 2004, fig. 6M-6S; Porter, 2008, pl. 2, fig. 15; see also Li, 1999, pl. 2, fig. 7; Ferná ndez Remolar, 2001a, fig. 3f). Pores are frequently preserved in chancelloriids from the Parara and Ajax limestones as small spines, 5-10 mm in diameter, that cover much of the surface of steinkerns, except on the basal facet and the facets between adjacent rays (Fig. 11.1-11.3, 11.6, 11.7). ...
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... fig. 6M-6S; Porter, 2008, pl. 2, fig. 15; see also Li, 1999, pl. 2, fig. 7; Ferná ndez Remolar, 2001a, fig. 3f). Pores are frequently preserved in chancelloriids from the Parara and Ajax limestones as small spines, 5-10 mm in diameter, that cover much of the surface of steinkerns, except on the basal facet and the facets between adjacent rays (Fig. 11.1-11.3, 11.6, 11.7). Where the outer surface of the sclerite has also been phosphatized, these spines extend like pillars across the cavity left by dissolution of the sclerite wall (Fig. 11.7). As shown by Vinther (2009, fig. 4), similar pores are also present (1,8,9,12) and as internal molds with a partial coating of the outside of the ...
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... limestones as small spines, 5-10 mm in diameter, that cover much of the surface of steinkerns, except on the basal facet and the facets between adjacent rays (Fig. 11.1-11.3, 11.6, 11.7). Where the outer surface of the sclerite has also been phosphatized, these spines extend like pillars across the cavity left by dissolution of the sclerite wall (Fig. 11.7). As shown by Vinther (2009, fig. 4), similar pores are also present (1,8,9,12) and as internal molds with a partial coating of the outside of the sclerite (2-7, 10, 11): 1, NIGP 152164; 2, NIGP 152117; 3, 7, NIGP 152136; 4-6, NIGP 152148; 8, 9, NIGP 152142; 10, 11, NIGP 152143; 12, NIGP 152149. Specimens are from the Xiaowan section ...
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... sachitids: steinkerns are often covered with small projec- tions, and specimens preserving the outer surface likewise show that the pores crossed the wall (Fig. 11.8-11.11). (In this paper we use the term sachitid to refer to members of the Sachitidae Meshkova, 1969, rather than to members of the larger group Sachitida He in Yin et al., 1980.) The thickness and length of these pore molds can vary between specimens, or between different areas of the same specimen, probably due to differences in ...
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... to refer to members of the Sachitidae Meshkova, 1969, rather than to members of the larger group Sachitida He in Yin et al., 1980.) The thickness and length of these pore molds can vary between specimens, or between different areas of the same specimen, probably due to differences in preservation (e.g., compare the upper and lower parts of Fig. 11.11). Pores are also present in halkieriid sclerites ( Bengtson et al., 1990, figs. 52D, 52E, 55O, 55P (although these were interpreted as not fully penetrating the wall); Yue, 2004, pl. 2, fig. H, pl. 3, fig. D, R; Porter, 2008, pl. 1, fig. 13; Vinther, 2009). (Sclerites of both the sachitid (5)(6)(7)(8)12) and as internal molds with a ...
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... same specimen, probably due to differences in preservation (e.g., compare the upper and lower parts of Fig. 11.11). Pores are also present in halkieriid sclerites ( Bengtson et al., 1990, figs. 52D, 52E, 55O, 55P (although these were interpreted as not fully penetrating the wall); Yue, 2004, pl. 2, fig. H, pl. 3, fig. D, R; Porter, 2008, pl. 1, fig. 13; Vinther, 2009). (Sclerites of both the sachitid (5)(6)(7)(8)12) and as internal molds with a partial coating of the outside of the sclerite (1-4, 9-11, 13-16). 13-16 are elemental maps; all others are scanning electron micrographs. 1-3, NIGP 152130; 4, NIGP 152131; 5-8, NIGP 152126; 9-11, Xiw103-09; 12, Xiw103-10; 13-16 are elemental ...
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... 80 mm for 10. Hippopharangites dailyi Bengtson in Bengtson et al., 1990, and the chancelloriid Archiasterella hirundo Bengtson in Bengtson et al., 1990, are also covered with tubercle-like projections on their outer surface [Bengtson, 2005;Porter, 2008], but the pores are much more numerous than the tubercles and appear to be unrelated to them [ Fig. 11.2, 11.3, ...
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... coeloscleritophorans is a verruculose basal facet. This has been noted in South Australian material of Chancelloria racemifundis Bengtson in Bengtson et al., 1990, Chancelloriella irregularis Demidenko, 2000, Eremactis conara Bengtson and Conway Morris in Bengtson et al., 1990, and E. mawsoni Bengtson and Conway Morris in Bengtson et al., 1990 (Fig. 11.4, 11.5; Bengtson et al., 1990;Demidenko, 2000;Gravestock et al., 2001), and in chancelloriids from Spain and Antarctica (Ferná ndez Remolar, 2001a, fig 3d; Wrona, 2004, fig. 6T). Bengtson (in Bengtson et al., 1990) refers to these verruculae as ''spherulitic deposits,'' but their internal structure remains unknown. Similar ...
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... Bengtson in Bengtson et al., 1990, Chancelloriella irregularis Demidenko, 2000, Eremactis conara Bengtson and Conway Morris in Bengtson et al., 1990, and E. mawsoni Bengtson and Conway Morris in Bengtson et al., 1990 (Fig. 11.4, 11.5; Bengtson et al., 1990;Demidenko, 2000;Gravestock et al., 2001), and in chancelloriids from Spain and Antarctica (Ferná ndez Remolar, 2001a, fig 3d; Wrona, 2004, fig. 6T). Bengtson (in Bengtson et al., 1990) refers to these verruculae as ''spherulitic deposits,'' but their internal structure remains unknown. Similar microstructures are also present on the lower surfaces of cap-shaped fossils that may be halkieriid valves (Conway Morris and Chapman, 1997; S.M.P., unpub. observations), the spine tips of ...
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... appear to have both the typical verruculae on the basal facet and diagenetically produced spherulitic apatite filling the foramen, illustrating the more irregular morphology of the latter (Fig. 6.8, 6.9). In a few specimens, however, there appears to be less difference between the verruculose texture and spherulitic apatite filling the foramen (Fig. 6.11) which may suggest that both have a diagenetic origin. The preservation on rare specimens of verruculae by a thin phosphatic crust overlying a hollow space (Fig. 6.5-6.7) suggests that they were originally calcareous; thus if they reflect diagenetic overgrowth they cannot have been originally phosphatic. In any case, that this texture ...
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... sclerite clusters are rare: in one sample from Xiaowan, 71 of 78 Cambrothyra specimens were isolated sclerites, seven were twins, and no pairs or clusters of sclerites were identified. Among chancelloriids s.s., in contrast, isolated rays with a complete outer wall have never been reported; isolated rays are only known from steinkerns (e.g., Fig. 11.1) or specimens that preserve only fragments of the outer wall ( Fig. 11.2, 11.3). Presumably the rays only dissociate from one another during laboratory preparation following dissolution of the calcareous walls that held them together. Although the different rays in chancelloriid sclerites were likely separated from each other by a thin ...
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... specimens were isolated sclerites, seven were twins, and no pairs or clusters of sclerites were identified. Among chancelloriids s.s., in contrast, isolated rays with a complete outer wall have never been reported; isolated rays are only known from steinkerns (e.g., Fig. 11.1) or specimens that preserve only fragments of the outer wall ( Fig. 11.2, 11.3). Presumably the rays only dissociate from one another during laboratory preparation following dissolution of the calcareous walls that held them together. Although the different rays in chancelloriid sclerites were likely separated from each other by a thin organic layer (Sdzuy, 1969, pl. 16, fig. 7b; Bengtson et al., 1990, fig. 37B, ...
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... difference between Cambrothyra and chancelloriids s.s. is that most Cambrothyra sclerites are entirely rounded in cross-section (Fig. 4.17-4.19), lacking the flattened sides or facets found in sclerites preserved in clusters ( Fig. 9.1-9.9) and occasional isolated sclerites (Fig. 4.10, 4.26). In pairs of Cambrothyra sclerites, each possesses a facet where they meet, but they lack the additional facets that would be present if they were once part of a larger compound sclerite. ...
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... difference between Cambrothyra and chancelloriids s.s. is that most Cambrothyra sclerites are entirely rounded in cross-section (Fig. 4.17-4.19), lacking the flattened sides or facets found in sclerites preserved in clusters ( Fig. 9.1-9.9) and occasional isolated sclerites (Fig. 4.10, 4.26). In pairs of Cambrothyra sclerites, each possesses a facet where they meet, but they lack the additional facets that would be present if they were once part of a larger compound sclerite. Conse- quently, we infer that the Cambrothyra scleritome included not only clusters of ...
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... difference between Cambrothyra and chancelloriids s.s. is that most Cambrothyra sclerites are entirely rounded in cross-section (Fig. 4.17-4.19), lacking the flattened sides or facets found in sclerites preserved in clusters ( Fig. 9.1-9.9) and occasional isolated sclerites (Fig. 4.10, 4.26). In pairs of Cambrothyra sclerites, each possesses a facet where they meet, but they lack the additional facets that would be present if they were once part of a larger compound sclerite. Conse- quently, we infer that the Cambrothyra scleritome included not only clusters of sclerites but also isolated sclerites, pairs of sclerites, and ...
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... and protoconodonts (reviewed in Vannier et al., 2007). Twin sclerites could represent either basal fusion of two sclerite buds or incipient division of one sclerite bud prior to mineralization; in either case they are far too common to be regarded as teratological. A tentative reconstruction of part of the Cambrothrya scleritome is shown in Fig. ...
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... in possessing sclerites similar to the twin sclerites of the latter. Most siphogonuchitid sclerites are isolated rays, but rare specimens preserve several sclerites fused in bundles or clusters (Qian and Bengtson, 1989;Bengtson, 1992;Conway Morris and Chapman, 1996). In some cases, each ray bears a separate foramen ( Voronin et al., 1982, pl. 7, fig. 11; Yang et al., 1983, pl. 1, fig. 11; He and Yang, 1986, pl. 1;Qian, 1989, pl. 45, figs. 1, 2;Ding et al., 1992, pl. 6, figs. 11, 12;Conway Morris and Chapman, 1996, figs. 7o-7q, 9a, 9b, 9e, 9f;Esakova and Zhegallo, 1996, pl. 11, fig. 15), while in others, different rays share a common foramen, similar to twin sclerites of Cambrothyra ( ...
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... the twin sclerites of the latter. Most siphogonuchitid sclerites are isolated rays, but rare specimens preserve several sclerites fused in bundles or clusters (Qian and Bengtson, 1989;Bengtson, 1992;Conway Morris and Chapman, 1996). In some cases, each ray bears a separate foramen ( Voronin et al., 1982, pl. 7, fig. 11; Yang et al., 1983, pl. 1, fig. 11; He and Yang, 1986, pl. 1;Qian, 1989, pl. 45, figs. 1, 2;Ding et al., 1992, pl. 6, figs. 11, 12;Conway Morris and Chapman, 1996, figs. 7o-7q, 9a, 9b, 9e, 9f;Esakova and Zhegallo, 1996, pl. 11, fig. 15), while in others, different rays share a common foramen, similar to twin sclerites of Cambrothyra ( Yang et al., 1983, pl. 1, figs. 12, ...
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... Morris and Chapman, 1996). In some cases, each ray bears a separate foramen ( Voronin et al., 1982, pl. 7, fig. 11; Yang et al., 1983, pl. 1, fig. 11; He and Yang, 1986, pl. 1;Qian, 1989, pl. 45, figs. 1, 2;Ding et al., 1992, pl. 6, figs. 11, 12;Conway Morris and Chapman, 1996, figs. 7o-7q, 9a, 9b, 9e, 9f;Esakova and Zhegallo, 1996, pl. 11, fig. 15), while in others, different rays share a common foramen, similar to twin sclerites of Cambrothyra ( Yang et al., 1983, pl. 1, figs. 12, 13;Qian and Bengtson, 1989, fig. 19;Qian, 1989, pl. 45, figs. 3, 4). Fan-like arrays of sclerites described as Dabashanites Chen, 1979, andMirusilites He andYang, 1986, are more complicated and ...
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... Cambrothyra does not possess a scleritome of compound sclerite rosettes like that of chancelloriids s.s., it does show a close resemblance to Eremactis and Monospinites, coeloscleritophorans described as single-rayed chancelloriids (Vasil'eva and Sayutina, 1988;Bengtson et al., 1990). Eremactis sclerites are elongate and spine-shaped ( Fig. 13.1- 13.7) but otherwise show many similarities with Cambrothyra (see descriptions in Bengtson et al., 1990;Gravestock et al., 2001;Skovsted, 2006). For example, the basal facet in Eremactis often has a verruculose texture ( Fig. 13.1; Bengtson et al., 1990, figs. 31F, 31G, 32B, 32H, 33E). Some Eremactis sclerites preserve numerous ...
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... (Vasil'eva and Sayutina, 1988;Bengtson et al., 1990). Eremactis sclerites are elongate and spine-shaped ( Fig. 13.1- 13.7) but otherwise show many similarities with Cambrothyra (see descriptions in Bengtson et al., 1990;Gravestock et al., 2001;Skovsted, 2006). For example, the basal facet in Eremactis often has a verruculose texture ( Fig. 13.1; Bengtson et al., 1990, figs. 31F, 31G, 32B, 32H, 33E). Some Eremactis sclerites preserve numerous highly elongate projections from the surface through an outer, presumably organic layer ( Fig. 13.2, 13.3, 13.8-13.10). Some of these projections occur on the lower surface of the sclerite, as they are found on the same side of the ...
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... in Bengtson et al., 1990;Gravestock et al., 2001;Skovsted, 2006). For example, the basal facet in Eremactis often has a verruculose texture ( Fig. 13.1; Bengtson et al., 1990, figs. 31F, 31G, 32B, 32H, 33E). Some Eremactis sclerites preserve numerous highly elongate projections from the surface through an outer, presumably organic layer ( Fig. 13.2, 13.3, 13.8-13.10). Some of these projections occur on the lower surface of the sclerite, as they are found on the same side of the sclerite as the basal facet; this is unusual for coeloscleritophorans (Bengtson, 2005;Porter, 2008) but projections are also sometimes present on the lower side of Cambrothyra sclerites (Figs. 5.18, ...
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... of the sclerite as the basal facet; this is unusual for coeloscleritophorans (Bengtson, 2005;Porter, 2008) but projections are also sometimes present on the lower side of Cambrothyra sclerites (Figs. 5.18, 6.12-6.14). Eremactis scler- ites also show variability in many of the same features as Cambrothyra: they range in shape from cylindrical ( Fig. 13.5, 13.7) to tapering to spindle-shaped ( Fig. 13.1), the basal facet ranges in orientation from approximately perpendicular (Fig. 13.1) to approximately parallel ( Fig. 13.2, 13.6) to the long axis of the sclerite, and the basal facet may or may not slope proximally to form a ''neck'' (present in Fig. 13.2-13.5; absent in Fig. 13.1, ...
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... for coeloscleritophorans (Bengtson, 2005;Porter, 2008) but projections are also sometimes present on the lower side of Cambrothyra sclerites (Figs. 5.18, 6.12-6.14). Eremactis scler- ites also show variability in many of the same features as Cambrothyra: they range in shape from cylindrical ( Fig. 13.5, 13.7) to tapering to spindle-shaped ( Fig. 13.1), the basal facet ranges in orientation from approximately perpendicular (Fig. 13.1) to approximately parallel ( Fig. 13.2, 13.6) to the long axis of the sclerite, and the basal facet may or may not slope proximally to form a ''neck'' (present in Fig. 13.2-13.5; absent in Fig. 13.1, 13.6). This variation has been used to erect four ...
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... sometimes present on the lower side of Cambrothyra sclerites (Figs. 5.18, 6.12-6.14). Eremactis scler- ites also show variability in many of the same features as Cambrothyra: they range in shape from cylindrical ( Fig. 13.5, 13.7) to tapering to spindle-shaped ( Fig. 13.1), the basal facet ranges in orientation from approximately perpendicular (Fig. 13.1) to approximately parallel ( Fig. 13.2, 13.6) to the long axis of the sclerite, and the basal facet may or may not slope proximally to form a ''neck'' (present in Fig. 13.2-13.5; absent in Fig. 13.1, 13.6). This variation has been used to erect four different species of Eremactis ( Bengtson et al., 1990;Gravestock et al., 2001) but ...
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... Cambrothyra sclerites (Figs. 5.18, 6.12-6.14). Eremactis scler- ites also show variability in many of the same features as Cambrothyra: they range in shape from cylindrical ( Fig. 13.5, 13.7) to tapering to spindle-shaped ( Fig. 13.1), the basal facet ranges in orientation from approximately perpendicular (Fig. 13.1) to approximately parallel ( Fig. 13.2, 13.6) to the long axis of the sclerite, and the basal facet may or may not slope proximally to form a ''neck'' (present in Fig. 13.2-13.5; absent in Fig. 13.1, 13.6). This variation has been used to erect four different species of Eremactis ( Bengtson et al., 1990;Gravestock et al., 2001) but they may not all be valid (cf. Skovsted, ...
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... they range in shape from cylindrical ( Fig. 13.5, 13.7) to tapering to spindle-shaped ( Fig. 13.1), the basal facet ranges in orientation from approximately perpendicular (Fig. 13.1) to approximately parallel ( Fig. 13.2, 13.6) to the long axis of the sclerite, and the basal facet may or may not slope proximally to form a ''neck'' (present in Fig. 13.2-13.5; absent in Fig. 13.1, 13.6). This variation has been used to erect four different species of Eremactis ( Bengtson et al., 1990;Gravestock et al., 2001) but they may not all be valid (cf. Skovsted, ...
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... cylindrical ( Fig. 13.5, 13.7) to tapering to spindle-shaped ( Fig. 13.1), the basal facet ranges in orientation from approximately perpendicular (Fig. 13.1) to approximately parallel ( Fig. 13.2, 13.6) to the long axis of the sclerite, and the basal facet may or may not slope proximally to form a ''neck'' (present in Fig. 13.2-13.5; absent in Fig. 13.1, 13.6). This variation has been used to erect four different species of Eremactis ( Bengtson et al., 1990;Gravestock et al., 2001) but they may not all be valid (cf. Skovsted, ...
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... Gravestock et al., 2001, SAMP 31006. Specimens are from the Ajax Limestone, Mount Scott Range, Flinders Ranges (1, 2, 5-9: sample UNEL 1872), and the Parara Limestone, Curramulka Quarry (3, 4, 10: sample UNEL 1846). Scale bars are 100 mm for 1-8 and 30 mm for 9 and 10. diagenetically fused Monospinites sclerites is known (Vasil'eva, 1998, pl. 22, fig. ...
Citations
... Most chancelloriid sclerites have a rosette form with up to about ten radiating hollow rays, each with a basal foramen for the passage of soft tissues connecting with the main body mass (Bengtson & Hou 2001, Yun et al. 2021b. Numerous morphotaxa have been introduced at the level of genus and species for sclerite morphologies with different numbers (one or more) and combinations of rays (summarized by Moore et al. 2010Moore et al. , 2014Moore et al. , 2019. Complete scleritomes are usually dominated by a single sclerite morphotype, but small numbers of other morphotypes may be present (Bengtson & Collins 2015). ...
... Chancelloriids, along with halkieriids, siphogonuchitids, and sachitids, were placed by Bengtson and Missarzhevsky (1981) in the Coeloscleritophora. This proposal was followed by some researchers (e.g., Qian and Bengtson, 1989;Bengtson et al., 1990;Bengtson, 2005;Porter, 2008;Moore et al., 2010), but again rejected by others because of the differences in anatomy between chancelloriids and the halkieriids: the former are cylindrically symmetrical whereas the latter are bilaterally symmetrical (Conway Morris and Peel, 1995;Vinther and Nielsen, 2005). Subsequently, chancelloriids have been considered to be related to tunicates (Mehl, 1996), cnidarians (Randell et al., 2005), mollusks (Conway Morris and Peel, 1995;Vinther and Nielsen, 2005; Conway Morris and Caron, 2007;Vinther, 2009), or to lie elsewhere in the early branches of the Metazoa (Janussen et al., 2002;Sperling et al., 2007). ...
A large number of well-preserved chancelloriid scleritomes from the Guanshan biota, early Cambrian of Yunnan, China, are described as a new species, Allonnia tenuis n. sp., and provide solid evidence for the original appearance of these enigmatic animals, based on specimens compacted laterally and top-down. With the assistance of a flexible integument, chancelloriids, especially Allonnia from early and middle Cambrian, may have had the ability to partially or completely expand and contract the body, which might have played an important role in feeding. A new metazoan with single-element spines, Nidelric gaoloufangensis n. sp., is also described. Preservation and affinity are discussed. Detailed comparison of the morphology of the body and spines of this metazoan indicate that it shares many similarities with chancelloriids, of which it may be an unusual form.
UUID: http://zoobank.org/2708d95a-1fae-46fc-afea-9707ae97a4d7
... 5), the oldest undoubted articulated sclerites of chancelloriids are known from beds that can be correlated with the upper Fortunian Stage in Siberia (Val'kov 1983;Khomentovsky et al. 1990; and this paper) and South China (Moore et al. 2014). These are reportedly preceded by such related forms as Cambrothyra ampulliformis Qian and Zhang, 1983 from the upper Anabarites trisulcatus-Protohertzina anabarica Assemblage Zone in South China (Moore et al. 2010), yet unknown in the coeval interval in Siberia. ...
... Apart from the oldest chancelloriids with central rays from the upper Fortunian, a probable relative of the chancelloriids is Cambrothyra ampulliformis (= truncata) Qian and Zhang, 1983, with single-rayed sclerites, is known from the lowermiddle Fortunian Assemblage Zone 1 of South China (Steiner et al. 2004a: fig. 2; Moore et al. 2010). ...
Assemblages of mineralized skeletal fossils are described from limestone rocks of the lower Cambrian Nemakit-Daldyn, Medvezhya, Kugda-Yuryakh, Manykay, and lower Emyaksin formations exposed on the western and eastern flanks of the Anabar Uplift of the northern Siberian Platform. The skeletal fossil assemblages consist mainly of anabaritids, molluscs, and hyoliths, and also contain other taxa such as Blastulospongia, Chancelloria, Fomitchella, Hyolithellus, Platysolenites, Protohertzina, and Tianzhushanella. The first tianzhushanellids from Siberia, including Tianzhushanella tolli sp. nov., are described. The morphological variation of Protohertzina anabarica and Anabarites trisulcatus from their type locality is documented. Prominent longitudinal keels in the anabaritid Selindeochrea tripartita are demonstrated. Among the earliest molluscs from the Nemakit-Daldyn Formation, Purella and Yunnanopleura are interpreted as shelly parts of the same species. Fibrous microstructure of the outer layer and a wrinkled inner layer of mineralised cuticle in the organophosphatic sclerites of Fomitchella are reported. A siliceous composition of the globular fossil Blastulospongia is reported herein and a possible protistan affinity similar to Platysolenites is discussed. New carbon isotope data facilitate correlation both across the Anabar Uplift and with the Terreneuvian Series of the IUGS chronostratigraphical scheme for the Cambrian System. The base of Cambrian Stage 2 is provisionally placed herein within the Fortunian‒Cambrian Stage 2 transitional interval bracketed by the lowest appearance of Watsonella crosbyi and by a slightly higher horizon at the peak of carbon isotope excursion Iʹ from western flank of the Anabar Uplift. Correlation across the Siberian Platform of the fossiliferous Medvezhya and lower Emyaksin formations showing δ13Ccarb excursion Iʹ with the upper Sukharikha Formation containing excursion 5p and upper Ust’-Yudoma Formation containing excursion I is supported herein.
... Janussen et al. (2002) recommended that no further chancelloriid species be erected on the basis of isolated sclerites. Although we concur that sclerite-based taxonomy of chancelloriids is difficult to reconcile with that based on whole bodies in Burgess-Shale-type preservation, there are good examples of three-dimensionally preserved sclerite associations with taxonomically useful characters that may serve to characterize composite scleritomes (Bengtson et al., 1990;Moore et al., 2010Moore et al., , 2014. A moratorium on sclerite-based taxonomy would therefore be counterproductive to the study of chancelloriid diversity and evolution. ...
... Spelling of Name. The spellings "Chancelloridae" and "Chancelloriidae" both occur in the modern literature (e.g., Janussen et al., 2002;Moore et al., 2010). Walcott (1920) based the family name Chancelloridae on the type and only genus Chancelloria. ...
... It was not until 1973 that Goryanskij pointed out that Walcott's Chancelloria eros was a heterogenous collection of taxa and that the morphology of chancelloriid "spicules" indicated them to be dermal skeletal elements. After Bengtson and Missarzhevsky (1981) argued that the mode of formation of chancelloriid sclerites precluded their homology with sponge spicules, most investigators have accepted (though sometimes with expressed hesitation) the flaws in the evidence for poriferan affinity (e.g., Grigor'eva and Zhuravleva, 1983;Rigby, 1983;Vasil'eva, 1985;Dzik, 1986;Rigby, 1986;Rozanov, 1986;Beresi and Rigby, 1994;Briggs et al., 1994;Dzik, 1994;Mehl, 1996;Chen and Zhou, 1997;Conway Morris, 1998;Mehl, 1998;Li, 1999;Demidenko, 2000;Fernández Remolar, 2001;Janussen et al., 2002;Beresi, 2003;Rigby and Collins, 2004;Wrona, 2004;Randell et al., 2005;Clausen and Álvaro, 2006;Porter, 2008;Kloss et al., 2009;Moore et al., 2010;Chen, 2012;Moore et al., 2014-but see Butterfield, 1995Butterfield and Nicholas, 1996;Botting and Butterfield, 2005;Sperling et al., 2007). ...
The cactus-like chancelloriids from the Middle Cambrian Burgess Shale are revised on the basis of Walcott’s (1920) original collections and new material containing several hundred specimens collected by Royal Ontario Museum field expeditions from 1975 to 2000. Walcott’s interpretation of chancelloriids as sponges was based on a misinterpretation of the dermal coelosclerites as embedded sponge-type spicules, an interpretation that further led to the lumping of three distinct taxa into one species, Chancelloria eros Walcott, 1920. The other two taxa are herein separated from C. eros and described as Allonnia tintinopsis n.sp. and Archiasterella coriacea n.sp., all belonging to the Family Chancelloriidae Walcott, 1920. Chancelloriids were sedentary animals, anchored to shells or lumps of debris in the muddy bottom, or to sponges, or to other chancelloriids. They had a radially symmetrical body and an apical orifice surrounded by a palisade of modified sclerites. Well-preserved integuments in Al. tintinopsis and Ar. coriacea do not show any ostium-like openings. Neither is there any evidence for internal organs, such as a gut. Partly narrowed specimens suggest that the body periodically contracted from the attached end to expel waste material from the body cavity. Chancelloriids were close in organization to cnidarians but shared the character of coelosclerites with the bilaterian halkieriids and siphogonuchitids. The taxon Coeloscleritophora is most likely paraphyletic.
... The Xihaoping Member is in turn overlain by silty shales of the Guojiaba Formation. Abundant small shelly fossils have been described from the Xihaoping Member, typically preserved as phosphatic internal molds or partially replaced casts (e.g., Qian and Zhang, 1983;Duan, 1984;Ding et al., 1990Ding et al., , 1992Steiner et al., 2004;Moore et al., 2010); in some cases, these molds include small patches of silica, phyllosilicates, or pyrite (personal observ.). Our sample (SXX-08-06 in Moore et al., 2010) revealed a diverse fauna upon acid maceration (Fig. 2), dominated by cambroclaves (Cambroclavus fangxianensis Qian and Zhang, 1983) and hyoliths (including many beautifully preserved examples of Conotheca brevica Qian, Xie, and He, 2001, as well as other indeterminate specimens). ...
... Abundant small shelly fossils have been described from the Xihaoping Member, typically preserved as phosphatic internal molds or partially replaced casts (e.g., Qian and Zhang, 1983;Duan, 1984;Ding et al., 1990Ding et al., , 1992Steiner et al., 2004;Moore et al., 2010); in some cases, these molds include small patches of silica, phyllosilicates, or pyrite (personal observ.). Our sample (SXX-08-06 in Moore et al., 2010) revealed a diverse fauna upon acid maceration (Fig. 2), dominated by cambroclaves (Cambroclavus fangxianensis Qian and Zhang, 1983) and hyoliths (including many beautifully preserved examples of Conotheca brevica Qian, Xie, and He, 2001, as well as other indeterminate specimens). Also relatively common are the problematic coeloscleritophorans Cambrothyra ampulliformis Qian andZhang, 1983, andAurisella tarimensis Qian andXiao, 1984; the possible chancelloriid Polycladium Qian and Xiao, 1984;the hyolith-like Cupitheca Duan in Xing et al., 1984; sponge spicules (including those of both hexactinellids and the possible heteractinid Xixiangites Ding and Li in Ding et al., 1992); as well as Cambroskiadeion and Acidocharacus, the subjects of this paper. ...
... It is possible that the long spine functioned as a site for the attachment of muscles (similar to an apodeme in an arthropod skeleton) or as a support for some soft organ. The verruculae on its base resemble textures found on the sclerites of some chancelloriids and of the chancelloriid-like animals Cambrothyra Qian and Zhang, 1983, and Eremactis Bengtson and Conway Morris in Bengtson et al., 1990(Bengtson et al., 1990Moore et al., 2010). They are also similar to verruculae found on Acidocharacus longiconus, as described below. ...
Phosphatized and phosphatic small shelly fossils are a major source of information concerning the evolution of animals during the early Cambrian. Although progress has been made in understanding some of these fossils, many remain enigmatic, both with regard to their phylogenetic affinities and the overall morphology of the animal from which isolated sclerites came. Two unusual fossils from the upper lower Cambrian (Qiongzhusian or Atdabanian) Xihaoping Member of the Dengying Formation from Xiaowan, Xixiang County, southeastern Shaanxi Province, China are described herein. The first of these is a cap-shaped fossil we describe as Cambroskiadeion xiaowanense new genus and species. On its concave surface it bears a spine, the base of which is covered with numerous hemispherical verruculae. The long spine indicates that this was a sclerite rather than a univalved shell, although it remains unclear from what sort of animal it came. Similar fossils have been hypothesized to be halkieriid valves; although the rarity of halkieriid sclerites in the present samples argues against this view, it is possible these fossils are part of a similar multi-element skeleton. The second fossil is Acidocharacus longiconus Qin and Ding, 1988; it is known only from the Xihaoping Member and consists of a tall spine, often bearing barbs or bumps, attached to a rounded conical base. The base is covered with verruculae similar to those found on Cambroskiadeion. The function of these elements, and whether they were internal or external, remains unknown.
... However, protolagenids are much larger (560-2400 mm) and they probably had biomineralized tests . Additionally, the Cambrian chancelloriid-like fossil Cambrothyra ampulliformis Qian and Zhang, 1983, when preserved as disarticulated sclerites, can be superficially similar to O. hyalina in having a restricted aperture with a raised rim often on a slightly depressed platform (Qian and Zhang, 1983;Qian et al., 2000;Moore et al., 2010). However, C. ampulliformis is clearly a multi-element skeletal organism and its sclerites (150-800 mm in maximum dimension) are much larger than the organic-wall vesicle of O. hyalina. ...
Abstract Silicified microfossils preserved in chert nodules of the Doushantuo Formation in the Yangtze Gorges area of South China have great potential to improve the biostratigraphic subdivision and correlation of the Ediacaran System. This potential can be realized only if solid taxonomy is available. However, a systematic treatment of these microfossils (particularly acanthomorphic acritarchs) is lacking, greatly limiting their biostratigraphic potential. This paper presents the systematic paleontology of silicified microfossils from upper Doushantuo Formation (Member III) chert nodules at three sections in the Yangtze Gorges area. More than 90 species of microfossils are described, including 66 named taxa of acanthomorphs, seven named taxa of sphaeromorphs, 12 taxa of cyanobacterial filaments and coccoids, four taxa of algal thalli, and two species of tubular microfossils. Several acritarch species, including Appendisphaera clava n. sp., Mengeosphaera grandispina n. sp., M. stegosauriformis n. sp., Leiosphaeridia, and possibly Sinosphaera rupina, are shown to be multicellular organisms, consistent with the proposition that some Ediacaran acritarchs may be diapause eggs of early animals. This study supports the view that the Tianzhushania spinosa acanthomorph biozone is unique to the lower Doushantuo Formation in South China (and perhaps its equivalent in northern India) and that Ediacaran acanthomorph assemblages from Australia, Siberia, and East European Platform are younger than the Tianzhushania spinosa biozone. It is proposed that the first occurrence of Hocosphaeridium anozos, a species with easily recognizable morphology and wide taphonomic and geographic distributions, be used to define the second Doushantuo acanthomorph biozone succeeding the Tianzhushania spinosa biozone. New taxa described in this paper include three new genera (Bispinosphaera n. gen.; Yushengia n. gen.; and Granitunica n. gen.) and 40 new species: Appendisphaera? brevispina n. sp., A. clava n. sp., A.? hemisphaerica n. sp., A. longispina n. sp., A. setosa n. sp., Bispinosphaera peregrina n. gen. n. sp., Crinita paucispinosa n. sp., Ericiasphaera densispina n. sp., Hocosphaeridium dilatatum n. sp., Knollisphaeridium denticulatum n. sp., K. longilatum n. sp., K. obtusum n. sp., K. parvum n. sp., Mengeosphaera angusta n. sp., M. bellula n. sp., M. cf. bellula n. sp., M. constricta n. sp., M.? cuspidata n. sp., M.? gracilis n. sp., M. grandispina n. sp., M. latibasis n. sp., M. minima n. sp., M. spicata n. sp., M. spinula n. sp., M. stegosauriformis n. sp., M. triangularis n. sp., M. uniformis n. sp., Sinosphaera asteriformis n. sp., Tanarium acus n. sp., T. elegans n. sp., T. longitubulare n. sp., T.? minimum n. sp., T. obesum n. sp., T. varium n. sp., Urasphaera fungiformis n. sp., U. nupta n. sp., Yushengia ramispina n. gen. n. sp., Granitunica mcfaddeniae n. gen. n. sp., Osculosphaera arcelliformis n. sp., and O. membranifera n. sp.
... This organism is treated as closely related to, but outside the Chancelloridae sensu stricto (Steiner et al. 2004a, fig. 2; Moore et al. 2010). ...
Data on the first appearances of major animal groups with mineralized skeletons on the Siberian Platform and worldwide are revised and summarized herein with references to an improved carbon isotope stratigraphy and radiometric dating in order to reconstruct the Cambrian radiation (popularly known as the ‘Cambrian explosion’) with a higher precision and provide a basis for the definition of Cambrian Stages 2 to 4. The Lophotrochozoa and, probably, Chaetognatha were first among protostomians to achieve biomineralization during the Terreneuvian Epoch, mainly the Fortunian Age. Fast evolutionary radiation within the Lophotrochozoa was followed by radiation of the sclerotized and biomineralized Ecdysozoa during Stage 3. The first mineralized skeletons of the Deuterostomia, represented by echinoderms, appeared in the middle of Cambrian Stage 3. The fossil record of sponges and cnidarians suggests that they acquired biomineralized skeletons in the late Neoproterozoic, but diversification of both definite sponges and cnidarians was in parallel to that of bilaterians. The distribution of calcium carbonate skeletal mineralogies from the upper Ediacaran to lower Cambrian reflects fluctuations in the global ocean chemistry and shows that the Cambrian radiation occurred mainly during a time of aragonite and high-magnesium calcite seas.
Chancelloriids are a poorly understood group of phylogenetically problematic Cambrian metazoans; complete specimens show they were sessile, radially symmetrical, club‐shaped organisms covered with sclerites in the form of rosettes of spines. While isolated sclerites are common components of Cambrian shelly assemblages, they have been relatively little studied. We describe chancelloriid sclerites from a series of nine sections spanning the upper Dyeran to lower Delamaran stages (latest Stage 4 to perhaps basal Wuliuan) from the Pioche–Caliente region of east‐central Nevada, USA. Acid maceration of samples from the Combined Metals, Comet Shale and Susan Duster Limestone members of the Pioche Formation yielded more than 2000 sclerites. Based on careful examination of these sclerites and statistical analyses of co‐occurring sclerite types, we distinguish six species, each with a restricted stratigraphic range. Chancelloria impar Moore sp. nov. is the dominant species in most upper Dyeran samples. Archiasterella cometensis Moore sp. nov. and A. auriculata Moore sp. nov. are rare in the upper Dyeran but abundant in the lowest Delamaran; A. uncinata Moore sp. nov. and C. lilioides Moore sp. nov. replace these in younger samples. A. auriculata is noteworthy for sharing features with species of both Archiasterella and Chancelloria. These results provide further support for the taxonomic tractability and biostratigraphical utility of chancelloriid sclerites; large collections from single horizons allow intraspecific variability to be assessed and species to be distinguished. Our results document a taxonomic turnover in chancelloriids at the Dyeran–Delamaran boundary, showing that not only trilobites were affected at this time.
Hyoliths are a group of Palaeozoic fossils with calcareous shells whose affinities remain controversial. As their shells were originally aragonitic, their fossils are usually coarsely recrystallized, and few data on their microstructure are available. We report hyoliths from the middle Cambrian (Drumian, Floran) Gowers Formation of the eastern Georgina Basin, Queensland. These are preserved as phosphatic internal moulds, often with the inner layers of the shell also partly replaced by phosphate. Microstructural details preserved by this early diagenetic phosphatization show that these hyolith conchs were originally composed of fibrous crystallites, c. 0.5 μm wide, parallel to one another and to the inner surface of the shell. In several species, the fibres are arranged in a plywood-like structure composed of multiple lamellae with a different fibre orientation in each lamella: often they are transversely oriented (relative to the long axis of the conch) in the inner part of the wall and longitudinally oriented in the outer part. Opercula also show a microstructure of parallel fibres. The lamello-fibrillar microstructure we report from hyoliths is reminiscent of microstructures of many Cambrian molluscs; that this microstructure is found in both conchs and opercula suggests that these structures are serial homologues of one another, and in this respect they resemble brachiopod valves. As with many other biological plywoods, the hyolith shell probably records self-organization in a liquid-crystal-like organic matrix. This provided a straightforward way to construct a material that could resist stresses from different directions, offering an effective defence against predators.
