Monday, December 3, 2012

Discovering the Newest Calyptraeid Species - Part 2 - Can we name it?

Finding something you think is new is the easy part.  Then the work really begins.  Before any species can be named it is important to demonstrate that it does not already have a name.  This sounds straightforward but it’s actually a lot like historical detective work.  Frustrating, fascinating, and under-appreciated by people who don’t do it themselves.

The type shells of two of the species described in 
the 1800s, kept at the British Museum and kindly 
photographed for us by their staff.  They look as 
good as new, you'd never guess they are almost 
200 years old!  From Veliz et al. 2012.

So, how did we go about that?  

The first step is to find all of the names that have been given to species in the genus Crepipatella.  This includes the currently recognized species, as well as any other species that have been synonymized with them.  Species are synonymized when two different species are named but are later found to be the same species.  This was not uncommon in the 1800s when access to publications was not as rapid as it is today.  It also happens when different individuals of one species look differen. For example males and females can look different and could have been described as different species.

When two species are synonymized the oldest name is the one that is used, and all of the younger names are considered “junior synonyms”.

When David and I started our search for names in 2009, two names, C. fecunda and C. dilatata, were in use in Chile. But it turned out that 14 species of Crepipatella were described from South America in the 1800s.  We knew the species discovered by David was not the same as C. fecunda or C. dilatata, but we had to check the 12 other species. 

The text and a figure from the original species description of 
Crepipatella nautiloides by Lesson in 1830.

We tracked down the original species descriptions, checked the associated figures, plates or illustrations – these often tell you much more than the short text - to determine if any of them matched our new species.  And finally – if they still exist - we checked the type specimen (the example of the species to which the name is formally attached) or their photos to see if they can tell us something useful. 

Shells of Crepipatella dilatata are on the 
top row, C. occulta in the middle row and 
C. fecunda (now called C. peruviana) on 
the bottom.  From Veliz et al. 2012.
The problem for us was that the old species descriptions are mostly based on shells, but our species show diagnostic genetic and developmental differences from the other two.  Luckily there is also a tendency for the shells to differ:  Crepipatella fecunda tends to have larger, more robust shells that are white on the inside. Crepipatella dilatata tends to have smaller streaky brownish-red shells and our species tends to have glossy chestnut shells.  But there is a lot of variation in each species.

Based on the geographic locations of these old species – some were collected 1000s of miles from the known range of our species – and the shell color, we were able to eliminate all of the previously named species and show that the species discovered by David more than 10 years ago really did need to be named. 

We chose the name occulta – The Latin adjective for hidden.  Since it looks just like the other Crepipatella species and has been hidden in plain sight for 100s of years.

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