The gang discusses two papers that investigate evidence of symbiosis in the fossil record. The first paper looks at wormy organisms living inside Cambrian vetulicolians, and the second paper shows potential evidence of hydroids growing in mollusc shells. Meanwhile, Amanda is haunted, James’s computer is totally cooperating, and Curt may or may not have had to stitch this podcast together from other sources.   Up-Goer Five (Curt Edition): The friends look at two papers that look at animals that live inside of other animals. Sometimes these things live inside other things and both of the things do well because of it. Sometimes, these things live inside other things and they cause problems for the thing they live in. These two papers look at the ways we can see old bits of things that used to live in other things and how we can try and figure out why they might have lived inside other things. The first paper looks long animals living inside a weird animal from a long long time ago. These long animals are all in a small part of these animals that looks like where these weird animals would breathe. Many long animals live inside one of these weird animals. The second paper looks at how hard parts of animals grow over things trying to live on them and we can use use the way these things grow to get an idea of what could have been living on them.   References: Li, Yujing, et al. "Symbiotic fouling of Vetulicola, an early Cambrian nektonic animal." Communications Biology 3.1 (2020): 517. Wisshak, Max, et al. "Putative hydroid  symbionts recorded by bioclaustrations in fossil molluscan shells: a  revision and reinterpretation of the cecidogenus Rodocanalis." Papers in Palaeontology 9.2 (2023): e1484.