Etymology: From aenigma (Gr.), mystery, arachne (Gr.), spider and sine (L.), without. The name was chosen because the spider in many respects is still a mystery and the male has no tibial apophyses.
The male of Aenigmarachne sinapophysis from Costa Rica is described. It is a small theraphosinae species belonging to the group where type VI urticating hairs are present. These spiders are distributed in Mexico and Central America. A. sinapophysis is the only species where the urticating hairs of that type are distally bent. In A. sinapophysis tibial spurs are absent. This species has a very long and bent embolus. The female is unknown. Therefore the relationship to other Central American genera of Theraphosinae has to remain vague for the time being.
