Key to extant species of Adelopoma

This attempt to key Adelopoma species is based on conchological features. Important diagnostic features, such as density of axial ribs and spiral striae, remain unknown for species described pre-2004. Moreover, we did not examine type material of earlier species and only rely on accuracy of the original descriptions of all taxa. Therefore, our proposed key is preliminary.

1 Species from Central America and Mexico ................................................................. 2

- Species from South American mainland or the southern Caribbean.............................................. 3

2 About 16 axial ribs on penultimate whorl............................................................ A. stolli

- About 7–9 axial ribs on penultimate whorl (‘24 are present on the first three whorls’ (Bartsch & Morrison 1942))................................................................................................. A. costaricense

3 About 12–15 axial ribs on ultimate whorl; northern Argentina, Bolivia, Paraguay ............................ A. tucma

- More than 15 axial ribs on ultimate whorl................................................................. 4

4 Up to 20 axial ribs on ultimate whorl..................................................................... 5

- Significantly over 20 axial ribs on ultimate whorl........................................................... 8

5 Shell height 2.5–2.9 mm; Atlantic coast of Brazil ............................................................ 6

- Shell height up to 2.6 mm; Ecuadorian and Peruvian Amazon and Andes......................................... 7

6 Protoconch of 1.5 whorl; shell height 2.6–2.9 mm ............................................... A. paulistanum

- Protoconch of 2 whorls; shell height up to 2.6 mm ................................................. A. brasiliense

7 Shell height 2.1–2.3 mm; about 16‒18 spiral ribs per 0.1 mm on ultimate whorl in apertural view; peristome nearly parallel to coiling axis in lateral profile........................................................ A. gracile Greķe, sp. nov.

- About 21‒22 spiral ribs per 0.1 mm on ultimate whorl in apertural view; peristome distinctly prosocline.... A. paraguayana

- About 11‒15 spiral ribs per 0.1 mm on ultimate whorl in apertural view; peristome distinctly prosocline..... A. peruvianum

8 About 33 axial ribs on ultimate whorl; southern Caribbean and northern Venezuela ....................... A. occidentale

- About 26 axial ribs on ultimate whorl; Venezuelan Andes............................................... A. bakeri