Morphology and taxonomy of Choia from the Qingjiang Biota
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Abstract:
Choia is one of the representative demosponges that occurred during the Cambrian Explosion. This genus has been discovered in a wide spectrum of the Cambrian biotas. However, the body shape and growth pattern of this sponge group remain controversial. In this paper, two new species of Choia, Choia qingjiangensis sp. nov. and Choia textura sp. nov. along with the common species C. carteri Walcott, 1920 from the Cambrian Stage 3 Qingjiang Biota are studied to reveal their morphology and taxonomy. The body shape and orientation of Choia are reconstructed based on new preservation models for this group. The results indicate that Choia can be categorized into two types based on different height-to-width ratios. The first type has a relatively large height-to-width ratio, making it more prone to lat eral compression, often resulting in fan-shaped or severely damaged specimens. The second type has a smaller height-to-width ratio, and is usually preserved as a round or nearly round shape due to the vertical pressure; the central disks of the specimens are often broken and the coronal spicules (i.e., large radially protruding spicules) are usually missing. The new specimens in this study support the concave side-upward reconstruction of Choia, shedding light on the adaptive strategies of this group.
