The coast of Southwest Florida hosts two species of the small-sized snail genus Truncatella: The Caribbean Truncatella, Truncatella caribaeensis Reeve, 1842 (maximum size 9 mm, or slightly more than 1/3 inch), and the Beautiful Truncatella, Truncatella pulchella Pfeiffer, 1839 (maximum size 0.65 mm, or about 1/4 inch). Truncatellas derive from marine ancestors but have adapted to live almost completely independently from the marine environment, except for the moment of fertilization, when male meets female in seawater. They live very close to the sea but above the high water line, usually in mangrove areas, and mostly under plant debris and other drift materials. The Caribbean Truncatella is the largest of the two species, differing also by its less marked, thinner outer lip (the expansion at the shell aperture, or opening), and the lack of a double outer lip, present in the slightly smaller Beautiful Truncatella.
The photos show, from left, the Caribbean Truncatella (Truncatella caribaeensis) and the Beautiful Truncatella (Truncatella pulchella); the arrow points to the “double outer lip” in this latter species. Photos by José H. Leal.