Snails are mollusks with distinctive spiral shells. Slugs are snail-like mollusks that have no shells. Easy to tell apart, right? But not so fast. Mollusks of the family Velutinidae are small marine mollusks that have a shell like a snail—but that shell is small and indistinct, and they wear it on the inside! This makes them look like slugs.

So, are velutinids slug-like snails or snail-like slugs? Inquiring minds want to know.

Recently, a group of researchers, with a little help from specimens from the OGL collections, tackled this mystery. They gave the caenogastropod superfamily Velutinoidea a complete makeover. Don’t worry if Velutinoidea hasn’t been on your radar; it wasn’t on anyone’s radar for over 30 years. This superfamily of gastropods was established in 1840, and all the subfamilies and species have mostly been identified by morphology (based on the structure of the animals). The issue with this is that velutinids vary a lot in appearance, even within species, and they have few distinct characteristics that can be used to tell species apart.

With the introduction of more modern DNA analysis tools, the ability to genetically identify species has become much more accessible. This is especially true for a family like Velutinidae, where species all have similar morphological identifiers.

In the new study, 316 specimens of the family Velutinidae were sampled from all over the globe (with three from OGL!). Then, they were put through a multitude of DNA-based and traditional morphological analyses to determine how these species are related to each other and to other known species.

The result? Two new subfamilies and two new genera! This is more than just your average new species discovery.

So, are velutinids slugs or snails? It turns out that they are neither. Instead, they are a unique group related to both but with their own distinct evolutionary origins—and now with new and newly-reorganized names. OGL is proud to have contributed to this important research.

The more you know!

Want to help OGL support great research like this? Donate to OGL.