Sponge spicule fossils from Member 3 of the Cambrian Qingxi Formation in the Sanjiang area, Guangxi
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Abstract:
Sponges (Porifera) are among the oldest metazoan groups, and their fossilized spicules are of great importance in sponge research. In this study, numerous sponge spicule fossils were discovered in a limestone layer of Member 3 of the Cambrian Qingxi Formation in the Sanjiang area, Guangxi, China. A systematic analysis was conducted to document the morphological characteristics of different types of these sponge spicules. The results indicate that the sponge spicules from Member 3 of the Qingxi Formation are abundant and diverse, with diaxonic tetractine spicules dominating and accounting for over 85% of the total. In addition, more complex forms, such as pentactines and orthotetraenes, were identified. Scanning electron microscopy (SEM) revealed the internal cross-sectional structures of axial canals within these spicules. Energy-dispersive X-ray spectroscopy (EDS) analysis showed that their elemental composition consists primarily of Si and O. Based on comparisons of morphological variations of these spicules, this study suggests that the sponges from Member 3 of the Cambrian Qingxi Formation in the Sanjiang area of Guangxi may have primarily formed grid-like structures composed of cross-shaped and X-shaped sponge spicules. These findings provide new data for the classification and evolutionary study of Cambrian sponge spicule fossils.
