Septation in shells of Frasnian gastropods from the Holy Cross Mountains

Amongst several known Paleozoic gastropod species having transverse septa in the apical parts of shells, three species (Straparollus aff. circularis, Orecopia kadzielniae and Donaldiella karczewskii) have been found in the Frasnian limestones of Grabina and Bolechowice-Panek in the Holy Cross Mountains (Central Poland). Septation in gastropod shells is a rare phenomenon and is an adaptive feature. Septa occur either in the thick-shelled gastropods living in high-energetic (reef) environments, preventing against negative effects of destruction of the apical parts of shells, or in the thin-shelled gastropods living on muddy substrate, lowering the inner volume of a habitable part of shell and increasing outer surface of gastropod body

Colour pattern of Naticopsis planispira (Neritimorpha, Gastropoda) shell from Upper Carboniferous of Upper Silesian Coal Basin, southern Poland

A zigzag colour pattern with additional collabral belts and irregular spots was observed on a shell of Naticopsis (N.) planispira (Phillips, 1836) found in the Gołonóg Sandstone marine faunal horizon (Namurian A, the Upper Silesian Coal Basin, Poland). A disruption in the colour pattern was also observed to have occurred during ontogenetic shell growth. In this specimen, it appeared in the healed shell damage on the outer lip. So far, only nine Carboniferous species of Naticopsis have been reported with the colour pattern preserved. The most common are the zigzag-type and the spiral band-type. Individual taxa clearly differ in the morphology of the chevrons (direction and angles of breaks) and the location and width of the spiral bands on a whorl. However, the color patterns may not be diagnostic features for the Naticopsis species, because of the large intraspecific variation and colour pattern polymorphism on the neritimorph shells. Colour patterns on Palaeozoic neritimorph shells most likely served as camouflage with respect to the bottom surface in the photic zone