Diagnosis.--Key characters: Ommatidial size coarse (Fig. 39b); prosternal process expanded apically (Fig. 18); mesal antennal spines present (Figs. 8b, 9b); pronotal impunctate regions present, although poorly-defined; femoral carinae absent; procoxal cavities closed laterally (Fig. 24); mesal profemoral apices rounded (as in Fig. 26d); metafemoral apices spinose (Figs. 8c, d, 9c, d); mesofemoral apices dentiform to weakly spinose (as in Fig. 25b); elytra with very sparse, translucent pubescence and visible costae; procoxal cavities open posteriorly (Fig. 18); pronotum without transverse ridges; mesotibial carinae absent; spine of antennomere three acute (Fig. 45a, b); mesofemoral shape gradually enlarged (Fig. 37c); antennomere three of males and females about half length of pronotum or less (Fig. 46a); peripheral pronotal calli pronounced; body very glabrous. Length: 23-30 mm.

Distribution and Diversity.--Southwestern United States to Panamá. Two species.

Discussion.--Based on the shared novel cell (Fig. 40c) feature, Atylostagma fell with Sphaerionillum in the phylogeny. They are part of a large polytomy, however, so further analysis needs to be made to discover their relationship to other genera.

The large size, pale integument with visible costae on the elytra, length of antennomere three less than half length of pronotum, and moderately to strongly bispinose elytral apices readily distinguish Atylostagma from other elaphidiines.