Sphaerionillum castaneum Click here for a larger view

Diagnosis.--Key characters: Ommatidial size fine (Fig. 39a); pronotum without transverse ridges; elytra without raised ivory calli; tibial carinae present (Fig. 22); femoral carinae absent; femora clavate (Fig. 37c); profemoral apices rounded (Fig. 26c, d); meso- and metafemoral apices rounded to dentiform (Figs. 25b, 26); lateral projections into mesocoxae from mesosternum present (Fig. 21); greatly expanded prosternal process between procoxae with posterior procoxal cavities closed (Fig. 27); median pronotal callus present; long, coarse, erect hairs sparsely, uniformly distributed over elytra and pronotum (similar to those in Fig. 16); elytra with pattern of large, pale maculations; elytral apicolateral spines weak; elytral sutural spines absent. Length: 11-16 mm.

Distribution and Diversity.--Guatemala, México. Three species.

Discussion.--This very distinctive genus was shown to be related to Atylostagma, although this is probably an artifact of the poor resolution in that part of the phylogeny (Fig. 50). More analysis is needed to fully understand the relationships in this basal portion of the tree.

The distinctive tapering elytra with sparse, uniformly- distributed coarse setae, pale maculations of the elytra, and closed procoxal cavities posteriorly readily characterize Sphaerionillum.