Belisana Thorell: high species diversity and male-female coevolution
(published in Zoologica, 2005; see Abstract, PDF (21 MB))
 

The genus Belisana previously contained only two nominal species. This paper added over 50 new species, mostly from SE Asia. Males have a pair of apophyses on their chelicerae that grasp a pair of female pockets during copulation. The distances between apophyses/pockets vary enormously among species, and provide an ideal and simply measured trait for male-female coevolution studies.

Photo: detail of the male genitalia of Belisana khaoyai; B. A. Huber