which are dated to the Early Cambrian; and those of other Early Cambrian fossils such as Ocruranus and Eohalobia. These similarities suggest that Orthrozanclus was an intermediate form between Wiwaxia and the Halkieriids and that all three of these taxa formed a monophyletic clade, in other words a group that consists of a common ancestor and all of its descendants. However this draws Orthrozanclus into a complex debate that has gone on since 1990 about whether Wiwaxia is more closely related to molluscs or to polychaete worms, and therefore about the entire "family tree" of the Lophotrochozoa, a "super-phylum" that is thought to contain modern molluscs, annelids and brachiopods as well as some extinct groups. The main opponent of this view, Nicholas Butterfield, proposes that Wiwaxia is more closely related to annelids while Halkieriids are very close to molluscs. Zhao et al. (2017) propose an alternative - that halkieriids (including orthrozanclus and halkieria) are unrelated to Wiwaxia, but are instead related to the camenellan tommotiids and thus belong in the brachiopod stem lineage. See also Burgess shale Halwaxiida References External links Spiky oddball prowled ocean half billion years ago. Yahoo UK & Ireland News New fossil unites three branches of life in the Cambrian. Ars Technica Burgess Shale fossils Taxa named by Simon Conway Morris Fossil taxa described in 2007 Maotianshan shales fossils Cambrian genus extinctions