The present study describes flexible nanofibrils in a Cambrian linguloid brachiopod Ungula inornata (Mickwitz, 1896).
After pilot examination of more than 10 specimens of Ungula inornata from different levels in the Maekalda (Mens et al.
The lower boundary of the Kallavere Formation is marked by the lingulate coquina containing numerous valves of linguloid brachiopods Ungula ingrica, Schmidtites celatus, rare Keyserlingia buchii and Oepikites obtusus.
The Ulgase Formation has yielded lingulate brachiopods Ungula inornata from all levels above the basal coquina, Ceratreta tanneri from the upper 3 m and Ungula sp.
As the shells were poorly preserved, but differed from the lingulate species formerly known in the region, they were referred to as Ungula sp.
Representatives of the genus Ungula have a baculate shell structure.
This shell architecture should be considered as the primary shell structure type of the genus Ungula.
It is important to note that the described feature of the shell structure of Ungula sp.