01576nas a2200193   4500008004100000245012800041210006900169300001200238490000700250520095100257653001401208653001101222653002101233653001901254100001601273700002001289700001901309856005401328       2010                        eng d00aCambrian Origin of All Skeletalized Metazoan Phyla--Discovery of Earth's Oldest Bryozoans (Upper Cambrian, Southern Mexico)0 aCambrian Origin of All Skeletalized Metazoan PhylaDiscovery of E  a547-5500 v383 a<p>Exquisite <em>Pywackia baileyi</em> Landing n. gen. and sp. specimens from the lower Tiñu Formation, southern Mexico, extend the bryozoan record into the Upper Cambrian. They are ∼8 m.y. older than the purported oldest bryozoans from South China, and show that all skeletalized metazoan phyla appeared in the Cambrian. The new form differs from similar, twig-like cryptostomes by its shallow autozooecia and an elongate axial zooid, which may be homologous to the stolon in nonmineralized ctenostomes. It may morphologically resemble mineralized stem group bryozoans that retained a stolon-like individual, although an ability to bud was acquired by the feeding individuals (autozooids). The latest Cambrian origin of bryozoans, several mollusk classes (polyplacophorans, cephalopods), and euconodonts was a major evolutionary development and can be considered the onset of the Ordovician radiation of more complex marine communities.</p>
10abryozoans10aMexico10aPywackia baileyi10aupper Cambrian1 aLanding, E.1 aEnglish, A., M.1 aKeppie, J., D.  uhttp://geology.gsapubs.org/content/38/6/547.short