Latest helcionelloid molluscs from the lower Ordovician of Kazakhstan

The helcionelloid mollusc Chuiliella elenae gen. et sp. nov. is described f rom the Lower Ordovician of Kazakhstan. It represents the geologically youn gest record of a group of mainly bilaterally symmetrical ancient molluscs w hich originated in the earliest Cambrian, flourished during the early-mid C ambrian and was thought to have become extinct during the late Cambrian. Ch uiliella is a typical helcionelloid in terms of shell shape, although the c omarginal ornamentation characteristic of many helcionelloids is lacking. I nterpretation of the raised margin of the aperture adjacent to the earlier coiled whorl as exhalant channels favours reconstruction of helcionelloids as endogastrically coiled, i.e., with the apex posterior.