The egg case genera ''[[Palaeoxyris]]'' and ''[[Fayolia]]'', which are thought to have been produced by [[hybodonts]] and [[Xenacanth|xenacanths]] respectively, two groups of extinct shark-like cartilaginous fish more closely related to modern sharks and rays than to chimeraschimaeras, resemble those of bulldog sharks in having a spiral band running around them. Both ''Palaeoxyris'' and ''Fayolia'' taper towards their ends (with the tapering being more pronounced in ''Palaeoxyris''), with one end having a tendril. Unlike modern sharks, these eggs are typically found in freshwater environments.<ref>{{Cite journal |last=Fischer |first=Jan |last2=Licht |first2=Martin |last3=Kriwet |first3=Jürgen |last4=Schneider |first4=Jörg W. |last5=Buchwitz |first5=Michael |last6=Bartsch |first6=Peter |date=2014-04-03 |title=Egg capsule morphology provides new information about the interrelationships of chondrichthyan fishes |url=http://www.tandfonline.com/doi/abs/10.1080/14772019.2012.762061 |journal=Journal of Systematic Palaeontology |language=en |volume=12 |issue=3 |pages=389–399 |doi=10.1080/14772019.2012.762061 |issn=1477-2019}}</ref>