The two smallest land snail species in the world have been discovered and described by an international research team led by Barna Páll-Gergely, a staff member of the Plant Protection Institute of the ELKH Centre for Agricultural Research (ATK). Angustopila psammion and Angustopila coprologos are currently the world's smallest land molluscs. The paper describing the discovery was published in the prestigious journal Contributions to Zoology.
The smallest known terrestrial mollusc was a Bornean snail species described in 2015, but it has now been overtaken by a species named Angustopila psammion (meaning 'grain of sand' in ancient Greek), found in a cave in northern Vietnam. The new species, which is the new global record-holder of the tiniest land snail title, has a maximum shell size ranging from 0.6 to 0.68 mm and a calculated volume of 0.036 mm3.
Another species of tiny snail, also recently discovered in Laos, is special because the living specimens have a spiral pattern of tiny mud granules on their shells. The most common explanation for similar patterns of behaviour is camouflage. If this is also true in this case, then a snail slightly larger than 0.6 mm will need to camouflage itself to avoid attack by a predator. Since the mud granules are probably made from the snails' faeces, the species is called Angustopila coprologos, which means 'dung gatherer' in ancient Greek.
Although slightly smaller marine species than the newly discovered snail species are known to man, these are currently the smallest found on dry land. The lower limit of the snail size is probably determined by two factors. One is that the newborn snail – which is about 0.2 mm in diameter – must have a sufficient number of nerve cells for its life processes to work, and the other is that the adult snail must be large enough to 'produce' at least one egg.