South American genus Guaranita includes tiny
spiders (body length ~1 mm) that lead reclusive lives under
ground-objects and run rapidly when disturbed. As a result, they have
been poorly collected and studied. Previous publications reported a
total of 58 adult specimens; molecular sequence data have been
available of only one species; and nothing has been known about
characters that require SEM (spinnerets; epiandrous spigots; tarsal
Here we report on a recent collection of more than 250 adult specimens of Guaranita spiders from Argentina, describing one new species and the previously unknown female of G. dobby. In addition, we provide CO1 barcodes for all (now five) known species, and first SEM data and first chromosome data for the genus. The diploid number of Guaranita goloboffi (2n♂ = 11) is among the lowest in araneomorph spiders with monocentric chromosome structure.