The hollow newel state in gastropods: when snail shells are open-axis.

This article examines the concept of holes in philosophy and their practical implications in zoological morphology, specifically in gastropod shells. The authors introduce different types of openings in gastropod shells, such as the true umbilicus, pseudoumbilicus, and a newly identified opening called the hollow newel. They propose that the axial openings in gastropod shells be designated as hollow newels, which lack complete inner shell walls forming the columella. The authors compare this concept to spiral staircases without a central supporting pillar. The text explores the presence of a hole, known as the "HN," in certain gastropod shells, discussing its attachment points for muscles and various character states associated with this feature. The authors conducted a survey and found that HNs are primarily found in turritellids. The text also delves into the potential functions and evolutionary significance of the HN. Overall, the article emphasizes the need for further research and examination of physical specimens to gain a better understanding of gastropod evolution and ecology. [Extracted from the article]