Fig. 4. Holotype UNAM 953 in New reticulosan sponges from the middle Cambrian of Sonora, Mexico

Fig. 4. Holotype UNAM 953 of the reticulosan sponge Ratcliffespongia arivechensis sp. nov. from the middle Cambrian El Mogallón Formation at Cerro El Mogallón, Sonora, Mexico. A. Skeletal layer with larger circular to elliptical parietal gaps. B. Detail showing reticulation of single skeletal layer. C. Enlargement showing that larger-order spicules are locally oriented with closely-spaced, aligned rays, combining to form straight or sinuous bundles.