Markuelia denotes a genus of fossil worm from the Middle Cambrian period that encompasses two known species, Markuelia hunanensis and Markuelia secunda, which are presumably the closest known relatives to three modern taxa of bilaterian animals: the Loricifera, Kinorhyncha and Priapulida.
Found in Hunan province in southern China and in eastern Siberia, these fossils represent many developmental stages from the first cell divisions to the time of hatching and therefore offer not only a unique opportunity to study the development of Lower Cambrian animals, but also yield remarkable insights into the phylogeny of the whole taxon, today known by the name of Scalidophora .
