The genus Villosa is a fairly large group of North America unionids that seem to be readily separated into distinct groups at the generic or subgeneric levels. Unfortunately, there are no available names for these groups. Many species readily separate into distinct populations based on shell characteristics; these may require subspecific rankings. We do not recognize the Antillean species assigned to this genus to be congeneric with Villosa.

This scheme is based solely on shell characteristics. The Division has begun a comprehensive genetic study of Villosa, and it will be interesting to see how closely the results of the two data sets match.

Maps are strictly approximations.

"Villosa" is broken down into the following taxa:

Villosa

Villosa     villosa
Villosa     amygdala
The lienosa Group
    Villosa       lienosa     lienosa
                                    caliginosa
                                    vanuxemi
                                    "North"
                                    "West"
                                    "Gulf"
                                    "Suwanee"
Villosa      ortmanni
Villosa      jonesii
Villosa      delumbis
Villosa      vaughaniana
Villosa      umbrans
"Villosa"    vibex

Genus A

"Villosa"    fabalis

Genus B

"Villosa"     trabalis     trabalis
                                perpurpurea

Genus C

The iris Group
    "Villosa"     iris   iris
                            novieboraci
                            "Missouri"
The nebulosa Group
    "Villosa"     nebulosa     nebulosa
                                      radians
Genus D

"Villosa"    arkansasensis
"Villosa"    constricta
"Villosa"    choctawensis

Genus E

"Villosa"     taeniata

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