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Hello everyone. Fairly new… just found these. Riverside County. Just trying to figure out what they are. They looked pretty interesting. Would anyone know what they are?

No idea what could it be, it is of stonish look and feel

Wisconsin Cambrian fossils in sandstone (aprox. 492 million years). Sharply defined rings. Very circular. Not irregular shaped like jellyfish. Any thoughts? Plus, If you can come up with a really good answer, you might get $500 Okay......The fossils aren't mine. They were found by amateur geologists Jerry Gunderson and Ron Meyer. They are part of a contest being done by the University of California Riverside. They are asking for people to prepare explanations for these fossil/geological features. And the best answer gets $500. (Or the best answers get to split the amount.) More details here with more photos, a video and descriptions. http://ringmaster.cs.ucr.edu/Rings.html They are looking at explanations to be submitted to their Reddit site. Here's observations they note about where the fossils were found and the size and depth of the rings. Ring diameters vary from about 2 cm to 11 cm, and the distribution of sizes appears to be a normal distribution. Cross sections through the rings (photos 3-5 above) suggest that if the rings formed at the seafloor (as opposed to within the sediment) they did so as grooves or ditches into the seafloor, rather than being upstanding circular structures such as the walls of a lunar crater. The grooves have apparently subsequently been infilled with sediment. Ring walls are 2-4mm wide and width is not obviously dependent on ring diameter – rather, it is related to what material the wall is cast in: rings cast by mud are narrower than those cast by sand. Rings extend down into the sediment as far as about 9 mm. Ring walls may have several layers of mud and sand within them – they were not necessarily filled up with sediment in a single episode of deposition. There is no indication of any structure preserved at the center of the rings. Ring walls are sharply defined compared to other structures in these rocks that are clearly animal burrows – hence the rings might have formed after the burrowing activity took place. Rings walls can be wider at the top of the ring than at the base, some even seem to have a slight bevel at the top. This is not the case in all rings. It is possible that some rings were originally slightly tilted relative to the sediment bedding because in several cases sections cut across the rings suggest that one side is slightly “higher” in the sediment than the other. It is not clear that this pattern existed at the times the rings formed: it could be an artifact that happened as the sediment experienced compaction. Ring distribution appears to be random on surfaces in which ring density is high. But where rings are distributed less densely, they tend to be dispersed, meaning their centers tend to be further apart from one another than chance would suggest. This may mean that rings forming at or near the same time were less likely to form in areas already occupied by other rings. The same rock unit is found commonly in the area, but these structures are only known at a single quarry. The rocks from this quarry are distinctive in the way they split well along bed partings so it is possible that the rings occur elsewhere but have not been recognized yet. We do not know whether the rings formed at the seafloor, or whether they formed within the sediment after the layers containing them were buried. When viewed in cross section there is nothing obvious either beneath or above the rings that throws any further light on their origins. The only structures associated with their formation are apparently the rings themselves.