Eight of 20 Sonoran specimens taken in May are females, each of which lacks epiphyseal sutures, and each contained one embryo.
"Neotropical Bats from Northern Mexico"
Sydney Anderson
Three of 8 Sonoran specimens taken in July had open epiphyseal sutures but were of adult size.
"Neotropical Bats from Northern Mexico"
Sydney Anderson
The latter two, however, are rather broadly distributed on the Great Plains and their assignment as Sonoran species is somewhat arbitrary.
"Mammals of Northwestern South Dakota"
Kenneth W. Andersen