Growth pattern of Fortunian scalidophoran sclerites

Fortunian scalidophoran worms have shown high diversity, with 7 genera and species 10 indeterminate forms. Current studies mainly focused on morphology as well early evolution, ontogeny not been carried out due to the limited number of specimens. Here, we report new material an Orsten-type preserved Indeterminate Form 3 from Zhangjiagou section. Collected specimens different annulus widths indicate presence several ontogenetic stages. We found newly formed sclerites at stages, suggesting that become more numerous in addition increasing size during growth. The large may also increase grow, however, their change.